Vibrational, NMR and quantum chemical investigations of acetoacetanilde, 2-chloroacetoacetanilide and 2-methylacetoacetanilide

Article abstract of DOI:10.1016/j.saa.2013.06.003

The vibrational assignment and analysis of the fundamental modes of the compounds acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA) have been performed. Density functional theory studies have been carried out with B3LYP method utilising 6-311++G ^** and cc-pVTZ basis sets to determine structural, thermodynamic and vibrational characteristics of the compounds and also to understand the influence of chloro and methyl groups on the characteristic frequencies of amide (-CONH-) group. intramolecular hydrogen bond exists in acetoacetanilide and o-substituted acetoacetanilide molecules and the N?O distance is found to be around 2.7 ?. The ¹H and ¹³C nuclear magnetic resonance chemical shifts of the molecules were determined and the same have been calculated using the gauge independent atomic orbital (GiAO) method. The energies of the frontier molecular orbitals have been determined. in AAA, 2CAAA and 2MAAA molecules, the n_N → pπ^*_co Interaction between the nitrogen lone pair and the amide C=O antibonding orbital gives strong stabilization of 64.75, 62.84 and 64.18 kJ mol ¹, respectively. The blue shift in amide-ii band of 2MAAA is observed by 45-50 cm¹ than that of AAA. The steric effect of ortho methyl group significantly operating on the N-H bond properties. The amide-iii, the C-N stretching mode of methyl and chloro substituted aceto-acetanilide compounds are not affected by the substitution while the amide-V band, the N-H out of plane bending mode of 2-chloroacetoacetanilide compound is shifted to a higher frequency than that of AAA. The substituent chlorine plays significantly and the blue shift in o-substituted compounds than the parent in the amide-V vibration is observed. The amide-Vi, C=O out of plane bending modes of 2MAAA and 2CAAA are significantly raised than that of AAA. A blue shift of amide-Vi, C=O out of plane bending modes of 2MAAA and 2CAAA than AAA is observed.

Full text of DOI:10.1016/j.saa.2013.06.003

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Vibrational, NMR and quantum chemical investigations
of acetoacetanilde, 2-chloroacetoacetanilide and
2-methylacetoacetanilide
a
a
b
V. Arjunan a, , M. Kalaivani , S. Senthilkumari , S. Mohan
⇑
a Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Puducherry 605 008, India
b School of Sciences and Humanities, VelTech University, Avadi, Chennai 600 062, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The FTIR and FT-Raman spectra of acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-meth-
ylacetoacetanilide (2MAAA) have been analysed. Quantum chemical studies were performed with B3LYP
method using 6-311++Gꢁꢁ and cc-pVTZ basis sets. The structural parameters, energies, thermodynamic
parameters, vibrational frequencies and the NBO charges were determined. The 1H and 13C isotropic
chemical shifts (d ppm) with respect to TMS were also calculated using the gauge independent atomic
orbital method. The delocaliation energy of the different types of bonding interactions was investigated.
The influences of chloro and methyl groups on the characteristic frequencies of amide (ACONHA) have
been discussed.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Spectral analysis of acetoacetanilide
and its derivatives were reported.
The n(N11) ? pꢁ(C13@O14)
interaction has strong stabilisation.
Blue shift (45–50 cmꢂ1) in amide-II
band of 2MAAA is observed than AAA.
The amide-III modes are not affected
by methyl and chloro substitution.
A blue shift of amide-VI modes of
2MAAA and 2CAAA than AAA is
observed.
a r t i c l e i n f o
a b s t r a c t
Article history:
The vibrational assignment and analysis of the fundamental modes of the compounds acetoacetanilide
(AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA) have been performed.
Density functional theory studies have been carried out with B3LYP method utilising 6-311++Gꢁꢁ and
cc-pVTZ basis sets to determine structural, thermodynamic and vibrational characteristics of the
compounds and also to understand the influence of chloro and methyl groups on the characteristic
frequencies of amide (ACONHA) group. Intramolecular hydrogen bond exists in acetoacetanilide and
o-substituted acetoacetanilide molecules and the Nꢃ ꢃ ꢃO distance is found to be around 2.7 Å. The 1H
and 13C nuclear magnetic resonance chemical shifts of the molecules were determined and the same have
been calculated using the gauge independent atomic orbital (GIAO) method. The energies of the frontier
Received 11 April 2013
Received in revised form 27 May 2013
Accepted 4 June 2013
Available online 20 June 2013
Keywords:
Acetoacetanilide
2-Chloroacetoacetanilide
2-Methylacetoacetanilide
molecular orbitals have been determined. In AAA, 2CAAA and 2MAAA molecules, the nN
?
pꢁCO interaction
DFT
between the nitrogen lone pair and the amide C@O antibonding orbital gives strong stabilization of 64.75,
62.84 and 64.18 kJ molꢂ1, respectively. The blue shift in amide-II band of 2MAAA is observed by
45–50 cmꢂ1 than that of AAA. The steric effect of ortho methyl group significantly operating on the
FTIR
NMR
⇑
Corresponding author. Tel.: +91 413 2211111, mobile: +91 9442635795; fax: +91 413 2251613.
E-mail address: varjunftir@yahoo.com (V. Arjunan).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.06.003

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
155
NAH bond properties. The amide-III, the CAN stretching mode of methyl and chloro substituted aceto-
acetanilide compounds are not affected by the substitution while the amide-V band, the NAH out of
plane bending mode of 2-chloroacetoacetanilide compound is shifted to a higher frequency than that
of AAA. The substituent chlorine plays significantly and the blue shift in o-substituted compounds than
the parent in the amide-V vibration is observed. The amide-VI, C@O out of plane bending modes of
2MAAA and 2CAAA are significantly raised than that of AAA. A blue shift of amide-VI, C@O out of plane
bending modes of 2MAAA and 2CAAA than AAA is observed.
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
chelates revealed that they were active against pathogenic fungal
strains.
Acetoacetanilide and its derivatives are used in manufacturing
agricultural chemicals, coating materials, dyes and pigments (the
dry colours generally referred to as Hansa and benzidine yellows)
as well as co-promoters for unsaturated polyesters. It is used in
the productions of pyrazolone, light yellow 5G, acid complex yel-
low GR, neutral dark yellow GL, hansa yellow G and pigment yel-
low G. It is used as the raw materials in agriculture products of
carboxin in pesticides, also can be used in medicine and organic
synthesis. Diketene derivatives of acetoacetic acid and heterocy-
cles have versatile applications including making agrochemicals,
dyes, pigments, pharmaceuticals and stabilisers for PVC and poly-
ester. Acetoacetanilide was known as chelating agent, and was
used for determination of Fe(III) by spectrophotometric methods.
Diazotisation of AAA leads to useful chelating agent.
Metazachlor is an acetoacetanilide herbicide used to control
broad leaved weeds and annual grasses. It can also be used on
ornamentals, nursery stock, in forestry and on wood land. It can
control gramineous weeds and dicotyledonous weeds in the cole,
soyabean, potato and tobacco fields. 2-Chloroacetoacetanilide
and 2-methylacetoacetanilide are used as intermediate for the syn-
thesis of organic pigments, pharmaceuticals and agrochemicals.
Recent studies suggest that organic materials have drawn sub-
stantial interest as potential candidates for applications in electro-
optic and photonic devices, such as digital optical switches, light
modulators, logic gates and high density optical data storage
devices [2,3]. Extensive experimental and theoretical investiga-
tions of conjugated organic materials exhibiting large optical
nonlinearities have been reported [4,5].
NLO organic materials are gaining widespread recognition and
are under intensive investigation owing to their potential applica-
tions in the field of optical signal processing [6,7]. To possess NLO
properties, organic molecules should contain a polar and highly con-
jugated p-electron system terminated with electron donor and
acceptor groups. Acetoacetanilide and its derivatives having consid-
erable interest, not least for their NLO properties, which make these
compounds highly attractive for applications in frequency doubling
of the light produced by semiconductor lasers [8,9].
Vijayan et al. [10] reported the growth and characterisation of
nonlinear optical (NLO) single crystal acetoacetanilide. Ravikumar
et al. [11] reported the vibrational contributions to the second-or-
der nonlinear optical properties of p-conjugated structure aceto-
acetanilide. But the structural, vibrational and 1H and 13C
chemical shifts of acetoacetanilide (AAA), 2-chloroacetoacetanilide
(2CAAA) and 2-methylacetoacetanilide (2MAAA) have not been
investigated. Thus, considering the industrial and biological impor-
tance of these compounds, extensive spectroscopic and theoretical
quantum chemical studies were carried out on AAA, 2CAAA and
2MAAA and to understand the effect of methyl and chloro group
on the characteristic frequencies of amide group.
The c-chloroacetoacetanilide is used as spectrophotometric indica-
tor for the EDTA titration of Fe (III) [1]. Bis-acetoacetanilide azo
yellow and orange pigments, dyes, and dyestuffs are well known
and are commonly used in various types of printing inks. They also
generally provide effective colouration to certain substrates, such
as plastics, paints, textiles, and the like. For example, Pigment Yel-
low 17 is a strong greenish-shade bis-acetoacetanilide yellow and
has often been incorporated within plastics. Diazo pigments ob-
tained from 3,3’-dichlorobenzidine and various acetoacetanilide
compounds, which do not contain any water-soluble groups, have
been used widely for the colouration of polyvinyl chloride resins,
printing inks, paints and rubber. Acetoacetanilideisonicotinylhyd-
razone and its metal chelate exhibit anticancer activity. The studies
on N-methylacetoacetanilideisonicotinylhydrazone and its metal
Experimental
The compounds acetoacetanilide, 2-chloroacetoacetanilide and
2-methylacetoacetanilide were prepared from the respective
aniline, 2-chloroaniline, 2-methylaniline and t-butylacetoacetate
with dry xylene as solvent using the reported procedure [12].
Scheme 1.
Table 1
Melting point and elemental analysis of the compounds.
Name of the compound
Melting point (°C)
% Found/(calculated)
C
H
N
Acetoacetanilide
2-Chloroacetoacetanilide
2-Methylacetoacetanilide
83
107
106
67.72 (67.78)
56.69 (56.75)
68.99 (69.08)
6.19 (6.26)
5.19 (5.24)
6.81 (6.85)
7.87 (7.91)
6.55 (6.62)
7.25 (7.32)

156
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
The reaction is represented by the Scheme 1. The pure samples of
aniline, 2-chloroaniline, 2-methylaniline, t-butylacetoacetate and
dry xylene were purchased from Aldrich chemicals, U.S.A and are
used as such without further purification. All other chemicals used
are of analar (AR) grade.
triple-f cc-pVTZ basis sets. Thus, the gradient corrected density
functional theory (DFT) [13] with the three-parameter hybrid
functional Becke3 (B3) [14,15] for the exchange part and the
Lee–Yang–Parr (LYP) correlation functional [16], calculations have
been carried out in the present investigation with Gaussian-09 [17]
program. The harmonic vibrational frequency calculations were
carried out resulting in IR and Raman frequencies together with
intensities and Raman depolarisation ratios.
The molecular electrostatic potential (MEP) serves as a useful
quantity to explain hydrogen bonding, reactivity and structure–
activity relationship of molecules including biomolecules and
drugs [18]. Isoelectronic molecular electrostatic potential surfaces
(MEP) and electron density surfaces [19] were calculated using
6-311++Gꢁꢁ basis set. The molecular electrostatic potential (MEP)
at a point ‘r’ in the space around a molecule (in atomic units) can
be expressed as:
0.1 mol each of dry aniline (9.31 g), 2-chloroaniline (12.76 g)
and 2-methylaniline (10.72 g), respectively is mixed with 15.82 g
(0.1 mol) of t-butyl acetoacetate in 25 ml of pure dry xylene. The
reaction mixture is then heated at 120 °C on a hot plate for about
15 min. The reaction was ceased after the evolution of t-butyl
alcohol. The reaction mixture is allowed to cool; the crude solid
products separate out. The synthesised crude compounds were
recrystallised from acetone several times. The total yield of prod-
ucts acetoacetanilide; pale yellow needle like crystalline powder;
m.p. 83–85 °C, 2-chloroacetoacetanilide; white or off-white pow-
der; m.p. 107 °C and 2-methylacetoacetanilide; white or off-white
powder; m.p. 104–106 °C is around 85%. The melting points were
uncorrected. The purity of the compounds was confirmed by
chemical analysis for C, H and N. The compounds prepared, the
melting point and elemental analysis are presented in Table 1.
The FTIR spectra of the compounds were recorded in the solid
phase by KBr disc method in a Bruker IFS66 V spectrometer in
Z
0
0
X
~
ZA
q
ðr Þdr
VðrÞ ¼
ꢂ
ꢀ!
0
~
~
jr ꢂ rj
~
j RA ꢂ rj
A
where ZA is the charge on nucleus A, located at RA and
q
(r0) is the
electronic density function for the molecule. The first and second
terms represent the contributions to the potential due to nuclei
and electrons, respectively. V(r) is the resultant at each point r,
which is the net electrostatic effect produced at the point r by both
the electrons and nuclei of the molecule. GaussView 5.0.8 visualisa-
tion program [20] has been utilised to construct the MEP surface
and the shape of frontier molecular orbitals.
the range 4000–400 cmꢂ1. The spectral resolution was 2 cmꢂ1
.
The FT-Raman spectra of these compounds were also recorded in
the range 4000–400 cmꢂ1 with the same instrument with
FRA106 Raman modules. The light scattering was excited using a
low-noise diode pumped Nd:YAG laser source operating at
1.064 lm with 200 mW power. A special (enhanced) liquid nitro-
gen cooled TGS detector was used. The frequencies of all sharp
bands are accurate to 2 cmꢂ1. The 1H (400 MHz; CDCl3) and 13C
(100 MHz; CDCl3) nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker HC400 instrument. Chemical shifts for pro-
tons are reported in parts per million scales (d scale) downfield
from tetramethylsilane.
The B3LYP method allows calculating the shielding constants
with accuracy. The 1H and 13C NMR isotropic shielding were calcu-
lated using the GIAO method [21,22] using the optimised parame-
ters obtained from B3LYP/6-311++Gꢁꢁ method. The effect of CDCl3
solvent on the theoretical NMR parameters was included using the
PCM model. The isotropic shielding constant values were used to
calculate the isotropic chemical shifts d with respect to tetrameth-
ylsilane (TMS). The chemical shifts were determined by the rela-
Computational details
tion diso(X) =
shift and riso – isotropic shielding constant.
r
iso(X)TMS
ꢂ
riso(X), where diso – isotropic chemical
Since the amide group is highly polarisable, the DFT study is
essential for the purpose of getting the structural parameters in
precision with the standard high level 6-311++Gꢁꢁ and the
The Raman scattering activities (Si) calculated by Gaussian 09W
program were suitably converted to relative Raman intensities (Ii)
Fig. 1. The stable geometry and atom numbering of (a) acetoacetanilide and (b) 2-chloro acetoacetanilide and (c) 2-methylacetoacetanilide.

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
157
Table 2
Structural parameters calculated for acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA) employing B3LYP methods with 6-
311++Gꢁꢁ and cc-pVTZ basic sets.
Structural parameters
AAA
2CAAA
Expt.a
2MAAA
Expt.b
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
Internuclear distance (Å)
C1AC2
C1AC6
C1AN11
C2AC3
C2AH24
C2ACl24
C2AC24
C3AC4
C3AH7
C4AC5
C4AH8
C5AC6
1.40
1.40
1.41
1.39
1.09
1.40
1.40
1.41
1.39
1.08
1.41
1.40
1.41
1.39
1.40
1.40
1.40
1.39
1.40
1.40
1.40
1.37
1.41
1.40
1.42
1.40
1.41
1.40
1.41
1.39
1.41
1.40
1.41
1.40
1.76
1.76
1.51
1.39
1.09
1.39
1.08
1.39
1.08
1.08
1.02
1.36
1.97
1.22
1.54
1.10
1.09
1.52
1.22
1.51
1.10
1.10
1.51
1.39
1.08
1.39
1.08
1.39
1.08
1.08
1.01
1.36
1.96
1.22
1.54
1.10
1.09
1.52
1.22
1.51
1.09
1.09
1.50
1.40
1.39
1.08
1.39
1.08
1.39
1.08
1.08
1.02
1.36
1.95
1.22
1.54
1.10
1.09
1.52
1.22
1.51
1.10
1.39
1.08
1.39
1.08
1.39
1.08
1.08
1.01
1.36
1.94
1.22
1.54
1.10
1.09
1.52
1.22
1.51
1.09
1.39
1.08
1.39
1.08
1.39
1.08
1.08
1.02
1.37
1.98
1.22
1.54
1.10
1.09
1.52
1.22
1.51
1.10
1.39
1.08
1.39
1.08
1.39
1.08
1.08
1.02
1.36
1.98
1.22
1.54
1.10
1.09
1.52
1.21
1.51
1.09
1.39
0.95
1.39
0.95
1.39
1.38
1.38
C5AH9
C6AH10
N11AH12
N11AC13
H12AO19
C13AO14
C13AC15
C15AH16
C15AH17
C15AC18
C18AO19
C18AC20
C20AH
0.95
0.88
1.36
1.36
1.22
1.52
0.99
0.99
1.51
1.22
1.50
0.98
1.23
1.52
1.51
1.22
1.50
C24AH
Bond angle (°)
C2AC1AC6
C2AC1AN11
C6AC1AN11
C1AC2AC3
C1AC2AH24
C3AC2AH24
C1AAC2ACl24
C3AC2ACl24
C1AC2AC24
C3AC2AC24
C2AC3AC4
C2AC3AH7
C4AC3AH7
C3AC4AC5
C3AC4AH8
C5AC4AH8
C4AC5AC6
C4AC5AH9
C6AC5AH9
119.5
116.9
123.6
120.5
119.6
120.0
119.4
117.0
123.7
120.5
119.5
120.0
117.6
118.9
123.5
121.7
117.6
119.0
123.5
121.7
117.1
117.2
125.7
123.4
120.2
117.3
122.5
118.2
120.2
117.4
122.5
118.3
120.1
116.4
123.5
118.0
120.0
118.3
120.0
118.3
121.6
120.2
121.8
118.5
119.6
119.2
120.1
120.7
120.6
120.3
119.1
120.0
119.3
120.8
116.8
128.9
114.1
125.9
115.2
118.8
106.8
106.3
119.3
106.5
106.1
111.2
121.9
116.5
121.7
109.3
110.3
110.6
109.7
106.8
110.3
121.6
120.2
121.8
118.5
119.6
119.2
120.2
120.7
120.6
120.3
119.1
120.0
119.2
120.8
116.9
129.0
113.9
126.2
115.1
118.7
106.8
106.3
119.2
106.4
106.1
111.2
122.1
116.4
121.5
109.4
110.3
110.5
109.7
106.7
110.2
121.6
120.4
121.7
120.3
119.4
120.3
119.2
120.4
120.5
121.3
119.9
118.8
119.3
119.7
121.0
116.4
128.8
114.6
125.7
115.3
119.0
106.7
106.4
119.7
106.2
106.1
111.0
122.1
116.3
121.6
109.2
110.3
110.6
109.6
106.8
110.3
120.3
119.4
120.3
119.2
120.4
120.5
121.3
119.9
118.8
119.4
119.6
121.0
116.5
128.9
114.4
125.9
115.1
118.9
106.7
106.4
119.6
106.2
106.0
111.1
122.3
116.2
121.4
109.3
110.2
110.6
109.7
106.7
110.3
119.9
119.1
121.0
119.3
119.8
120.9
120.9
120.1
118.9
120.6
118.6
120.8
116.7
128.0
115.2
125.5
115.5
119.0
106.8
106.2
119.2
106.5
106.1
111.3
121.8
116.4
121.9
109.3
110.2
110.6
109.6
106.8
110.2
119.9
119.1
121.0
119.3
119.8
120.8
120.9
120.1
118.9
120.6
118.5
120.9
116.6
128.2
115.1
125.7
115.3
119.0
106.9
106.3
119.0
106.5
106.0
111.3
121.9
116.3
121.7
109.4
110.2
110.5
109.7
106.7
110.2
118.8
120.6
119.6
120.2
120.2
120.9
119.6
119.6
120.3
119.8
119.8
118.0
128.1
113.9
124.6
116.3
119.2
106.8
106.8
122.1
106.8
106.8
106.8
123.3
115.8
123.9
109.5
109.5
109.5
109.5
109.5
109.5
119.2
120.6
120.4
C1AC6AC5
C1AC6AH10
C5AC6AH10
C1AN11AH12
C1AN11AC13
H12AN11AC13
N11AC13A014
N11AC13AC15
O14AC13AC15
C13AC15AH16
C13AC15AH17
C13AC15AC18
H16AC15AH17
H16AC15AC18
H17AC15AC18
C15AC18AO19
C15AC18AC20
O19AC18AC20
C18AC20AH21
C18AC20AH22
C18AC20AH23
H21AC20AH22
H21AC20AH23
H22AC20AH23
128.9
124.8
116.2
119.0
122.5
121.2
(continued on next page)

158
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Table 2 (continued)
Structural parameters
AAA
2CAAA
Expt.a
2MAAA
Expt.b
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
C2AC24AH25
C2AC24AH26
C2AC24AH27
H25AC24AH26
H25AC24AH27
H26AC24AH27
112.0
112.3
110.4
107.1
107.4
107.5
112.0
112.3
110.4
106.9
107.4
107.6
a
Values taken from Ref. [24].
Values taken from Ref. [25].
b
using the following relationship derived from the basic theory of
Raman scattering [23].
present between the ketone carbonyl and the amide NAH groups.
The Nꢃ ꢃ ꢃO distance is seen to be 2.77 Å in AAA, 2.79 Å in 2CAAA and
2.79 Å in 2MAAA. The hydrogen bond distance Oꢃ ꢃ ꢃH is shorter in
AAA (1.95 Å) than that of o-substituted compounds. This is due
to steric effect of chloro and methyl groups. The substituents do
not affect the amide group parameters. The acetyl group (ACOCH3)
is not planar with respect to anilide part of the molecules. This is
confirmed from the dihedral angle C13AC15AC18AC20 and is
found to be 144°, 142.2° and 141.2° in AAA, 2CAAA and 2MAAA
molecules, respectively.
4
fðm0
ꢂ
miÞ Si
Ii ¼
mi½1 ꢂ expðꢂhc i=kTÞꢄ
m
where v0 is the exciting frequency (cmꢂ1), vi is the vibrational
wavenumber of the ith normal mode, h, c and k are universal
constants, and f is the suitably chosen common scaling factor for
all the peak intensities.
The bond lengths between the amide nitrogen and the aromatic
ring, C1AN11 and between the amide nitrogen and the carbonyl
group, N11AC13 given in Table 2 reflect the changes in conjuga-
tion. The C1AN11 bond distance slightly increases in 2MAAA than
that of AAA and 2CAAA. In 2MAAA the adjacent methyl group
influence on the rotation of acylamino group. As the steric
hindrance increases and the plane of acylamino group rotates,
the C1AN11 bond becomes longer and the N11AC13 bond be-
comes shorter. The hyperconjugative effect of ACH3 group on the
C1AN11 bond distances is also plays the role. The C2AC1AC6 bond
angle is shorter in 2CAAA (117.6°) than that of AAA (119.5°) and
2MAAA (120.2°). This is due to the presence of the AI effect of elec-
tron withdrawing ACl group in 2CAAA.
Results and discussion
Structural properties
The optimised geometry and the scheme of atom numbering of
AAA, 2CAAA and 2MAAA are represented in Fig. 1. The bond
lengths and the bond angles for the optimised geometry of AAA,
2CAAA and 2MAAA at B3LYP levels with 6-311++Gꢁꢁ and cc-pVTZ
basis sets are presented in Table 2. The CAC and CAH bond lengths
are found to be not significantly affected by Cl and ACH3 substitu-
tions. The bond length of the compounds AAA, 2CAAA and 2MAAA
determined at the DFT level of theory are in good agreement with
the XRD results [24,25]. All the compounds AAA, 2CAAA and
2MAAA adopt trans planar configuration at the amide and non-pla-
nar acetyl group however, the nature of the hydrogen bonding
defines the orientation of the ketone carbonyl with respect to the
amide. An intramolecular hydrogen bonding C@Oꢃ ꢃ ꢃHAN is
With the electron donating methyl substituent on the benzene
ring of 2MAAA, the symmetry of the ring is distorted, yielding
ring angles smaller than 120° at the point of substitution and
slightly larger than 120° at the ortho and meta positions [26].
Table 3
The calculated thermodynamic parameters of acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA) employing B3LYP methods with
6-311++Gꢁꢁ and cc-pVTZ basis sets.
Thermodynamic parameters (298 K)
AAA
2CAAA
2MAAA
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
B3LYP/6-311++Gꢁꢁ
B3LYP/cc-pVTZ
SCF energy, (Hartrees)
ꢂ593.0793
128.4
126.6
120.7
45.2
ꢂ593.1282
128.6
126.8
120.9
45.0
ꢂ1052.6998
123.1
121.3
114.7
49.0
ꢂ1052.7578
123.3
121.5
114.9
48.8
ꢂ632.4054
146.7
145.0
138.1
51.1
ꢂ632.3060
144.8
143.0
137.8
43.9
Total energy (thermal), Etotal (kcal molꢂ1
)
Vibrational energy, Evib (kcal molꢂ1
)
Zeropoint vibrational energy (kcal molꢂ1
Heat capacity, Cv (cal molꢂ1 Kꢂ1
Entropy, S (cal molꢂ1 Kꢂ1
)
)
)
112.5
112.2
119.4
119.3
119.9
105.6
Rotational constants (GHz)
X
Y
Z
1.95
0.40
0.34
1.95
0.40
0.34
1.04
0.38
0.29
1.05
0.38
0.29
1.41
0.39
0.31
1.41
0.39
0.31
Dipolemoment (Debye)
lx
ly
lz
ltotal
2.88
2.87
ꢂ2.18
ꢂ2.15
2.97
1.65
0.30
3.41
2.97
1.66
0.29
3.42
ꢂ1.17
ꢂ1.17
ꢂ0.05
ꢂ0.00
ꢂ0.27
ꢂ0.29
ꢂ0.13
ꢂ0.17
3.12
3.12
2.18
2.16
ELUMO
ELUMO (eV)
EHOMO (eV)
EHOMOꢂ1 (eV)
ELUMOꢂHOMO (eV)
(eV)
1
ꢂ0.7886
ꢂ1.5209
ꢂ6.2608
ꢂ7.0492
4.7400
ꢂ0.6041
ꢂ1.3328
ꢂ6.1691
ꢂ6.9852
4.8363
ꢂ1.0036
ꢂ1.4779
ꢂ6.4494
ꢂ7.0652
4.9716
ꢂ0.8498
ꢂ1.2874
ꢂ6.3509
ꢂ6.9909
5.0635
ꢂ0.7578
ꢂ1.5206
ꢂ6.1417
ꢂ6.7928
4.6211
ꢂ0.5802
ꢂ1.3443
ꢂ6.0573
ꢂ6.7341
4.7130
+

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
159
Fig. 2. The total electron density surface mapped with electrostatic potential of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c) 2-methylacetoacetanilide.
The angle at the point of substitution C1AC2AC3 is 118.0° while
the bond angle at ortho position to the ACH3 substitution
C2AC3AC4 is 121.7°. Introduction of electron attracting chloro
group leads to significant perturbations in the ring, in a reverse
manner. The bond angle C1AC2AC3 is 123.4° where the ACl
group is attached while at ortho, C2AC3AC4 position the angle
is found to be 118.8°.
The energies and thermodynamic parameters of the compounds
AAA, 2CAAA and 2MAAA have also been computed at B3LYP meth-
ods with 6-311++Gꢁꢁ and cc-pVTZ basis sets and are presented in
Table 3. The frequency calculations compute the zero point ener-
gies, thermal correction to internal energy, enthalpy, Gibbs free en-
ergy and entropy as well as the heat capacity for a molecular
system. The calculated SCF energy of the compounds clearly
indicates that 2CAAA is more stable than AAA and 2MAAA. From
Table 3 it is observed that the dipole moment of 2MAAA is higher
than the dipole moments of AAA and 2CAAA due to the presence of
the electron donating ACH3 group.
Determination of molecular electrostatic potential
To understand the relative polarity [27] the molecular electro-
static potential surface (MEP) of the molecular complex has been
determined by B3LYP/6-311++Gꢁꢁ method [28]. The total electron
density mapped with electrostatic potential surface which displays
electrostatic potential (electron + nuclei) distribution, molecular
shape, size and dipole moments of the molecules AAA, 2CAAA
and 2MAAA are shown in Fig. 2. The MEP surface of the compounds
is represented in the Supplementary Figure S1 and the electrostatic
potential contour map for positive and negative potentials are also
shown in Fig. 3.
The electron rich and partially negative charge of the MEP
surface is shown in red colour, the blue region reveals the electron
deficient and partially positive charge, light blue region shows
slightly electron deficient region, the slightly electron rich region
is indicated by yellow and the green colour shows neutral. It is
obviously from the Figs. 2 and 3 that the region around carbonyl
Fig. 3. The contour map of electrostatic potential of the total density of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c) 2-methylacetoacetanilide.

160
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Fig. 4. The frontier molecular orbitals and their energy gap of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c) 2-methylacetoacetanilide.
Table 4
oxygen atoms represents the most negative potential region (red).
The hydrogen atoms attached to the ends of methyl and methylene
group posses the maximum bang of positive charge (blue). The pre-
dominance of green region in the MEP surfaces corresponds to a
potential halfway between the two extremes red and dark blue col-
our. The total electron density of the molecule 2CAAA
Atomic charges of acetoacetanilide (AAA), 2-chloroacetoacetanilide (2ClAAA) and
2-methylacetoacetanilide (2MAAA) by NBO analysis using B3LYP/6-311++Gꢁꢁ
method.
Atom
AAA
0.15639
2CAAA
2MAAA
C1
C2
C3
C4
C5
C6
H7
H8
0.13253
ꢂ0.05765
ꢂ0.21407
ꢂ0.20670
ꢂ0.18754
ꢂ0.21521
0.22005
0.20838
0.20757
0.25014
ꢂ0.62860
0.43723
0.69221
ꢂ0.61555
ꢂ0.56267
0.25535
0.23764
0.59073
ꢂ0.5669
ꢂ0.66617
0.23008
0.22904
0.22352
0.15560
ꢂ0.05134
ꢂ0.19290
ꢂ0.21444
ꢂ0.19270
ꢂ0.22434
0.19938
0.20328
ꢂ0.22686
ꢂ0.19120
ꢂ0.22181
ꢂ0.18430
ꢂ0.23020
0.20502
0.20457
0.20468
0.24535
ꢂ0.61846
0.42210
0.68691
ꢂ0.62062
ꢂ0.56419
0.25575
0.23854
0.59471
ꢂ0.57907
ꢂ0.66708
0.23175
0.22907
0.22389
0.20504
(+4.82e ꢅ 10ꢂ2 to ꢂ4.82e ꢅ 10ꢂ2
)
is smaller than 2MAAA
(+5.19e ꢅ 10ꢂ2 to ꢂ5.19e ꢅ 10ꢂ2
)
and AAA (+5.19e ꢅ 10ꢂ2 to
ꢂ5.19e ꢅ 10ꢂ2) is due to the presence of the ꢂI effect of chlorine
in 2CAAA.
H9
0.20396
Analysis of frontier molecular orbitals
H10
N11
H12
C13
O14
C15
H16
H17
C18
O19
C20
H21
H22
H23
H24
Cl24
C24
H25
H26
H27
0.24513
ꢂ0.62693
0.42779
0.68842
ꢂ0.61883
ꢂ0.56358
0.25486
0.23781
0.59416
ꢂ0.57926
ꢂ0.66678
0.23173
0.22861
0.22414
Well known concepts such as conjugation, aromaticity and lone
pairs are well illustrated by molecular orbitals. The energies of
HOMO, LUMO, LUMO + 1 and HOMO – 1 and their orbital energy
gap are calculated by using B3LYP/6-311++Gꢁꢁ method and the
pictorial illustration of the frontier molecular orbitals and their
respective positive and negative regions are shown in Fig. 4.
The positive and negative phase is represented in red and green
colour, respectively. The region of HOMO and LUMO levels spread
over the entire molecule and the calculated energy gap of LUMO–
HOMO’s explains the ultimate charge transfer interface within the
molecule. The frontier orbital energy gap in the case of AAA, 2CAAA
and 2MAAA are found to be 4.7400, 4.9716 and 4.6211 eV,
respectively.
0.00662
ꢂ0.60425
0.21051
0.21588
0.21408
Topological charge distributions
The natural atomic charges of AAA, 2CAAA and 2MAAA calcu-
lated by natural population analysis by using the B3LYP/ 6-
311++Gꢁꢁ method is presented in Table 4. In all these compounds
among the ring carbon atoms C1 has a positive charge while oth-
ers have negative charge. The positive charge of C1 is due to the
attachment of highly electronegative nitrogen atom (N11) to it. In
both the 2CAAA and 2MAAA compounds the C2 carbon has less

Table 5
Second order perturbation theory analysis of Fock matrix of acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methyl acetoacetanilide (2MAAA) by B3LYP/6-311++Gꢁꢁ method.
Donor (i)–acceptor (j) interaction
AAA
2CAAA
2MAAA
E(2)a (kJ molꢂ1
)
E(j) –E(i)b (a.u.)
F(i, j)e (a.u.)
E(2)a (kJ molꢂ1
)
E(j) –E(i)b (a.u.)
F(i,j)e (a.u.)
E(2)a (kJ molꢂ1
)
E(j)–E(i)b (a.u.)
F(i,j)e (a.u.)
r
r
r
(C1AC2) ? rꢁ(C1AC6)
(C1AC2) ? rꢁ(C2AC3)
(C1AC6) ? rꢁ(C1AC2)
4.12
2.91
4.24
18.76
3.12
3.70
1.27
1.29
1.26
0.28
1.26
1.11
1.28
0.29
0.28
0.29
1.28
1.08
1.10
0.28
0.28
1.10
1.10
1.10
1.08
1.09
1.07
1.09
1.22
1.25
1.06
0.53
0.52
1.11
0.52
0.89
0.30
0.27
0.72
0.60
0.67
0.67
0.065
0.055
0.065
0.065
0.056
0.057
0.053
0.070
0.069
0.065
0.053
0.058
0.056
0.066
0.070
0.057
0.058
0.064
0.058
0.057
0.061
0.058
0.062
0.072
0.062
0.053
0.057
0.063
0.053
0.052
0.090
0.120
0.119
0.101
0.100
0.104
4.28
3.59
5.18
19.82
4.05
3.50
1.28
1.30
1.24
0.27
1.27
1.15
1.32
0.29
0.30
0.31
1.28
1.06
1.11
0.28
0.26
1.09
1.11
1.12
1.07
1.10
1.05
1.10
1.22
1.26
1.06
0.53
0.52
1.12
0.53
0.89
0.29
0.27
0.72
0.61
0.66
0.67
0.066
0.061
0.072
0.066
0.064
0.057
0.058
0.070
0.069
0.064
0.062
0.063
0.055
0.068
0.072
0.055
0.057
0.062
0.059
0.057
0.059
0.058
0.062
0.071
0.061
0.054
0.056
0.063
0.052
0.053
0.092
0.119
0.120
0.101
0.101
0.105
4.39
3.09
4.79
19.67
3.51
3.89
1.26
1.28
1.25
0.29
1.25
1.10
1.28
0.29
0.28
0.29
1.28
1.07
1.10
0.28
0.28
1.10
1.10
1.10
1.08
1.10
1.06
1.10
1.23
1.26
1.05
0.53
0.52
1.11
0.52
0.89
0.30
0.27
0.72
0.60
0.67
0.67
0.066
0.056
0.069
0.067
0.059
0.059
0.058
0.069
0.068
0.067
0.059
0.062
0.056
0.067
0.069
0.057
0.057
0.063
0.058
0.058
0.061
0.057
0.059
0.072
0.061
0.053
0.056
0.063
0.053
0.052
0.089
0.120
0.119
0.101
0.099
0.104
p
(C1AC6) ? pꢁ(C2AC3)
r
r
r
p
p
p
(C2AC3) ? rꢁ(C1AC2)
(C2AC3) ? rꢁ(C1AN11)
(C2AC3) ? rꢁ(C3AC4)
2.78
3.24
3.25
(C1AC6) ? pꢁ(C4AC5)
(C2AC3) ? pꢁ(C1AC6)
(C2AC3) ? pꢁ(C4AC5)
21.33
20.45
17.81
2.79
3.86
3.56
19.11
22.04
3.68
3.77
4.64
3.88
3.72
4.36
3.80
3.87
5.12
4.52
5.90
7.66
4.44
6.58
3.76
33.95
64.75
23.74
20.47
18.19
19.47
20.92
19.02
16.36
3.76
4.67
3.39
20.35
23.63
3.45
3.64
4.27
4.07
3.68
4.13
3.82
3.93
4.97
4.44
5.99
7.46
4.46
6.30
3.80
35.90
62.84
24.24
20.26
18.79
19.77
20.67
19.84
19.37
3.70
4.46
3.56
19.73
20.70
3.69
3.66
4.46
3.87
3.66
4.39
3.75
3.57
5.14
4.47
5.81
7.52
4.51
6.49
3.77
32.89
64.18
23.73
20.51
18.11
19.49
r
r
r
p
p
(C3AC4) ? rꢁ(C2AC3)
(C3AH7) ? rꢁ(C1AC2)
(C3AH7) ? rꢁ(C4AC5)
(C4AC5) ? pꢁ(C1AC6)
(C4AC5) ? pꢁ(C2AC3)
r
r
r
r
r
r
r
r
r
r
r
r
r
r
r
(C4AH8) ? rꢁ(C2AC3)
(C4AH8) ? rꢁ(C5AC6)
(C5AC6) ? rꢁ(C1AN11)
(C5AH9) ? rꢁ(C1AC6)
(C5AH9) ? rꢁ(C3AC4)
(C6AH10) ? rꢁ(C1AC2)
(C6AH10) ? rꢁ(C4AC5)
(N11AH12) ? rꢁ(C1AC6)
(N11AH12) ? rꢁ(C13AO14)
(C13AC15) ? rꢁ(C1AN11)
(C15AH16) ? pꢁ(C13AO14)
(C15AH16) ? pꢁ(C18AO19)
(C15AH17) ? rꢁ(C18AO19)
(C20AH21) ? pꢁ(C18AO19)
(C20AH22) ? rꢁ(C15AC18)
n(LP(1)N11) ? pꢁ(C1AC6)
n(LP(1)N11) ? pꢁ(C13AO14)
n(LP(2)O14) ? rꢁ(N11AC13)
n(LP(2)O14) ? rꢁ(C13AC15)
n(LP(2)O19) ? rꢁ(C15AC18)
n(LP(2)O19) ? rꢁ(C18AC20)
a
b
e
Stabilisation (delocalisation) energy.
Energy difference between i(donor) and j(acceptor) NBO orbitals.
Fock matrix element i and j NBO orbitals. LP – lone pair.

162
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
negative charge than that of AAA. This is due to the attachment of
chlorine and methyl groups at C2 carbon in 2CAAA and 2MAAA.
The very high positive charge resides on the carbonyl carbon
atoms C13 and C18 because of the partial polar nature of C@O
group. This also leads to more negative charge on the oxygen
atoms O14 and O19.
Donor–acceptor interactions
The natural bond orbital (NBO) demonstrates the bonding con-
cepts like atomic charge, Lewis structure, bond type, hybridisation,
bond order, charge transfer and resonance possibility. The stabili-
sation of orbital interaction is proportional to the energy difference
Fig. 6. 1H NMR spectrum of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide
and (c) 2-methylacetoacetanilide.
Fig. 5. 13C NMR spectrum of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide
and (c) 2-methylacetoacetanilide.
Table 6
The experimental and calculated 13C isotropic chemical shifts (diso, ppm) with respect to TMS and isotropic magnetic shielding constants (
riso) of acetoacetanilde (AAA),
2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA).
Assignment
AAA
2CAAA
13C)
2MAAA
13C)
Expt. (diso)
riso
(
13C)
Cal. (diso
)
Expt. (diso
)
riso
(
Cal. (diso
)
Expt. (diso
)
riso
(
Cal. (diso)
C1
C2
C3
C4
C5
C6
C13
C15
C18
C20
C24
36.62
60.75
49.06
54.65
48.42
59.87
15.19
131.48
ꢂ36.52
148.99
147.91
123.78
135.47
129.88
136.11
124.66
169.34
53.05
137.62
120.34
128.94
124.64
128.94
120.34
164.54
50.69
35.60
60.78
49.85
52.78
44.24
46.98
18.75
129.69
ꢂ35.74
149.17
148.93
123.75
134.68
131.75
140.29
137.55
165.78
54.84
134.58
122.19
127.49
125.00
129.18
123.57
163.86
49.71
38.13
50.92
47.73
55.22
51.04
60.12
15.38
130.48
ꢂ36.46
148.90
163.60
146.4
133.61
136.8
129.31
133.49
124.41
169.15
54.05
135.66
129.31
130.47
125.18
126.55
122.88
163.89
49.53
221.05
35.54
204.41
30.75
220.27
35.36
204.66
31.01
220.99
35.63
20.93
205.33
31.01
17.81

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
163
between interacting orbitals. Therefore, the interaction having
strongest stabilisation takes place between effective donors and
effective acceptors. This bonding–anti bonding interaction can be
quantitatively described in terms of the NBO approach that is
expressed by means of second-order perturbation interaction en-
ergy E(2) [29–32]. This energy represents the estimate of the off-
diagonal NBO Fock matrix element. The stabilization energy E(2)
associated with i(donor) ? j(acceptor) delocalisation is estimated
from the second-order perturbation approach [33] as given below
the range 100–200 ppm [37–39]. The ꢂI effect of nitrogen (N11)
reduces the electron density of the carbon atom C1, thus its NMR
signal is observed in the downfield at 137.62, 134.58 and
135.66 ppm in the case of AAA, 2CAAA and 2MAAA, respectively.
The chemical shift of other ring carbon atoms of AAA, 2CAAA and
2MAAA lie in the range 128.94–120.34, 129.18–122.19 and
129.31–122.88 ppm, respectively. The acetyl methyl group carbon
(C20) of all the three molecules gives the NMR absorption at
31 ppm. In 2MAAA the methyl carbon (C24) shows signal at
17.8 ppm. This clearly reveals that the acetyl methyl carbon
(C20) atom found in the downfield due to the adjacent highly polar
carbonyl group. The methylene group carbon (C15) gives signal in
the upfield at around 50 ppm. This is due to the attachment of elec-
tron withdrawing nature of the adjacent two carbonyl groups. The
acetyl carbonyl carbon atom C18 of AAA, 2CAAA and 2MAAA com-
pounds are significantly observed in the downfield with chemical
shift value 204.41, 204.66 and 205.33 ppm while the amide car-
bonyl carbon atom C13 of AAA, 2CAAA and 2MAAA compounds
are observed at 164.54, 163.86 and 163.89 ppm, respectively. This
clearly reveals the highly polar nature of acetyl carbonyl group
than the amide carbonyl group.
The NMR spectra of the compounds were thoroughly analysed to
quantify the possible different effects acting on the shielding con-
stant of protons. In the case of AAA, 2CAAA and 2MAAA compounds
the peaks due to ACH3 and ACH2A groups appear in the up field re-
gions at 2.29, 1.97, 2.30 and 3.56, 3.63, 3.59 ppm, respectively. The
signal of ACH2A protons is shifted to downfield than that of ACH3
protons due to electrons withdrawing C@O groups present on
either side of ACH2A group. The NH proton signal of AAA, 2CAAA
and 2MAAA compounds appears as a singlet at about 9.20, 9.58
and 9.17 ppm, respectively. The aromatic ring protons produce sig-
nal between 7 and 7.5 ppm. The hydrogen atoms present in the
benzene ring of AAA and 2MAAA compounds shows NMR peaks
in the narrow range 7.11–7.53 and 7.17–7.87 ppm while the 2CAAA
shows in the region 5.06–8.32 ppm. A good agreement between the
calculated and experimental chemical shift values are observed
from Table. 7. The linear regression between the experimental
and theoretical 1H and 13C NMR Chemical shifts of AAA, 2CAAA
and 2MAAA are represented in Figs. 7 and 8. The correlations of
the experimental chemical shift with that of the shielding constants
are illustrated in the Supplementary Figs. S2 and S3.
F2ði; jÞ
Eð2Þ ¼ q
i ej
ꢂ
ei
where qi is the donor orbital occupancy, ei and ej are diagonal
elements (orbital energies) and F(i,j) is the off-diagonal Fock matrix
element.
The types of donor–acceptor interactions and their stabilisation
energies of AAA, 2CAAA and 2MAAA are determined by analysing
the Fock matrix and summarised in Table 5. In AAA, 2CAAA and
2MAAA molecules, the lone pair donor orbital, nN
tion between the nitrogen lone pair and the C13@O14 antibonding
orbital has strong stabilisation of 64.75, 62.84 and 64.18 kJ molꢂ1
respectively. The lone pair donor orbital, nN
pꢁCC interaction be-
?
pꢁCO interac-
,
?
tween the nitrogen lone pair and the C1AC6 antibonding orbital
gives stabilisation of 33.95, 35.90 and 32.89 kJ molꢂ1, respectively.
In AAA, 2CAAA and 2MAAA molecules, the bond pair donor orbital,
pCC
?
pꢁCC interaction between the C1AC6 bond pair and the C2AC3
antibonding orbital give stabilisation of 18.76, 19.82 and
19.67 kJ molꢂ1 and also the interaction between the C1AC6 bond
pair and the C4AC5 antibonding orbital gives more stabilisation
with 21.33, 20.92 and 20.67 kJ molꢂ1
.
NMR spectral investigations
NMR spectroscopy is a powerful tool to derive structural infor-
mation and it involves the change of the spin state of a nuclear
magnetic moment when the nucleus absorbs electromagnetic radi-
ation in a strong magnetic field [34]. Thus, NMR techniques are
used to detect the presence of particular nuclei in a compound
for a given nuclear species. And, it is also an important tool for
the identification of molecules and for the examination for their
electronic structure [35,36]. The observed 13C and 1H NMR spectra
of the compounds AAA, 2CAAA and 2MAAA are given in the Figs. 5
and 6, respectively. The 13C and 1H theoretical and experimental
chemical shifts, isotropic shielding constants and the assignments
of the compounds AAA, 2CAAA and 2MAAA are presented in Tables
6 and 7. Aromatic carbons give signals with chemical shift values in
Vibrational analysis
The geometry of AAA, 2CAAA and 2MAAA molecules possessing
C1 point group symmetry. A total of 66 fundamental modes of
Table 7
The Experimental and calculated 1H isotropic chemical shifts (diso, ppm) with respect to TMS and isotropic magnetic shielding constants (
r
iso) of acetoacetanilde (AAA),
2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA).
Assignment
AAA
2CAAA
2MAAA
Expt. (diso)
riso (1H)
Cal. (diso
)
Expt. (diso
)
riso (1H)
Cal. (diso
)
Expt. (diso
)
riso (1H)
Cal. (diso)
H7
H8
H9
24.42
24.65
24.31
23.03
22.03
28.50
28.29
29.38
29.92
29.37
24.77
7.55
7.32
7.66
8.94
9.94
3.47
3.68
2.59
2.05
2.60
7.20
7.31
7.11
7.31
7.53
9.20
3.56
3.56
2.29
2.29
2.29
7.53
24.71
24.81
24.54
25.31
22.42
28.62
28.44
29.47
30.00
29.47
7.26
7.16
7.43
6.66
9.55
3.53
3.53
2.5
7.36
5.06
7.27
8.32
9.58
3.63
3.63
1.97
1.97
1.97
24.57
24.77
24.52
22.96
22.30
28.42
28.26
29.36
29.93
29.36
7.4
7.2
7.17
7.18
7.06
7.87
9.17
3.59
3.59
2.30
2.30
2.30
7.45
9.01
9.67
3.55
3.71
2.61
2.04
2.61
H10
H12
H16
H17
H21
H22
H23
H24
H25
H26
H27
1.97
2.5
29.44
29.32
29.62
2.53
2.65
2.35
2.31
2.31
2.31

164
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Fig. 8. The linear regression between the experimental and theoretical 13C NMR
Chemical shifts (d) of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c)
2-methylacetoacetanilide.
Fig. 7. The linear regression between the experimental and theoretical 1H NMR
Chemical shifts (d) of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c)
2-methylacetoacetanilide.
substituents but by the form of substitution around the ring [40],
although heavy halogens diminish the frequency [41]. In AAA,
the ring carbon–carbon stretching bands are appeared in the infra-
red spectrum at 1619, 1600, 1499, 1446, 1315 and 1161 cmꢂ1. The
corresponding CAC stretching modes are observed in the Raman
spectrum at 1603, 1501, 1451, 1309 and 1161 cmꢂ1. In the case
of 2CAAA the bands observed in the infrared spectrum at 1598,
1594, 1470, 1442, 1281 and 1264 cmꢂ1 and 1597, 1593, 1474,
1282 and 1257 cmꢂ1 in Raman spectrum are attributed to the cor-
responding CAC stretching modes. The CAC stretching bands of
2MAAA are observed in the infrared spectrum at 1612, 1550,
1491, 1296 and 1267 cmꢂ1 while at 1613, 1545, 1492, 1268 and
1194 cmꢂ1 in Raman spectrum. The electron withdrawing nature
of chlorine in the ring lowers the CAC stretching vibrations of
2CAAA than that of AAA and 2MAAA. The mode observed at 995
and 1000 cmꢂ1 in the IR and Raman spectra is assigned to the
trigonal bending of AAA. The mode observed at 991 cmꢂ1 in the
vibrations are possible for AAA and 2CAAA while 2MAAA produce
75 fundamental modes of vibrations. All the vibrations are active in
both IR and Raman. The FTIR and FT-Raman spectra of AAA, 2CAAA
and 2MAAA are shown in Figs. 9 and 10, respectively. All the ob-
served wavenumbers are assigned in terms of fundamentals, over-
tones and combination bands. The observed and calculated
frequencies along with their relative intensities and probable
assignments are presented in Tables 8–10.
Carbon–carbon vibrations
The carbon–carbon stretching modes of the phenyl group are
expected in the range from 1650 to 1200 cmꢂ1. The actual position
of these mode are determined not so much by the nature of the

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
165
Fig. 9. FTIR spectrum of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c) 2-methylacetoacetanilide.
Raman spectrum is assigned to the trigonal bending of 2CAAA. The
trigonal bending mode of 2MAAA is attributed to 994 and
990 cmꢂ1 in the IR and Raman spectra, respectively. The observed
and calculated CCC in-plane and out of plane bending modes of all
the compounds are assigned and presented in Tables 8–10. These
results are in good agreement with the literature values [42–45].
observed in the region 1300–850 cmꢂ1 and are usually weak. The
CAH out of plane bending modes are usually medium intensity
[45–48] arises in the region 950–600 cmꢂ1. In the case of AAA
the bands observed at 1167, 1155 and 1075 cmꢂ1 in IR spectrum
are assigned to the CAH in-plane bending vibrations. The CAH
in-plane bending modes of 2CAAA are assigned to the
wavenumbers at 1150, 1080, 1051, 1037 cmꢂ1 in IR and at 1164,
1038 cmꢂ1 in Raman spectra. The CAH in-plane bending modes
of the compound 2MAAA are also assigned to the wavenumbers
at 1049, 1039 cmꢂ1 in IR and at 1062 cmꢂ1 in Raman spectra.
The CAH out of plane bending modes of the compounds are also
assigned and presented in the Tables 8–10.
CAH vibrations
The aromatic compounds show CAH stretching vibrations in
the region 3100–3000 cmꢂ1. In AAA these modes are observed at
3138, 3086, 3072, 3067 and 3046 cmꢂ1 in IR spectrum and at
3069, 3059 cmꢂ1 in Raman spectrum. The bands observed in the
infrared spectra of 2CAAA at 3118, 3080, 3069, 3004 cmꢂ1 and at
3080, 3072 cmꢂ1 in Raman spectrum are attributed to the corre-
sponding CAH stretching modes. The bands observed in the infra-
red and Raman spectra of 2MAAA at 3121, 3083, 3049 and
3053 cmꢂ1 are assigned to the CAH stretching vibrations. In aro-
matic compounds the CAH in-plane bending vibrations are
Keto (C@O) group vibrations
The acetyl keto (C@O) stretching vibration is expected in the
region 1760–1730 cmꢂ1 [48,49]. In AAA the C@O stretching is
observed in IR as a strong band at 1713 cmꢂ1 and a very weak band
at 1715 cmꢂ1 in Raman spectra. In 2CAAA, the C@O stretching is

166
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Fig. 10. FT-Raman spectrum of (a) acetoacetanilide and (b) 2-chloroacetoacetanilide and (c) 2-methylacetoacetanilide.
observed in IR as very strong band at 1713 cmꢂ1. In 2MAAA the
very strong C@O stretching band is observed in IR at 1708 cmꢂ1
The acetylketo stretching vibration is not at all influenced by the
ring substituents. In the present work, the C@O in-plane and out
of plane bending vibrations of both the compounds are assigned
and given in Tables 8–10.
The medium band observed at 3294 cmꢂ1 in IR is attributed to
the NAH stretching of AAA molecule. The molecules 2CAAA and
2MAAA shows the characteristic medium NAH stretching bands
at 3206 and 3271 cmꢂ1 in the IR spectrum. The influence of the
ring substituent on NAH stretching frequency of acetoacetanilide
and its derivatives may be the resultant steric effect, direct field ef-
fects, hydrogen bonding and bond polarisation effects. The increase
in NAH stretching frequency may be expected in introduction of an
o-methyl or t-butyl group into the phenyl ring. In the present
investigation, it is observed that there is no rise in the NAH
stretching frequency of 2MAAA than that of acetoacetanilide. This
clearly confirms that the steric effect due to o-methyl group is not
significantly operating on the NAH stretching vibration. In 2CAAA,
the expected lowering of NAH stretching frequency than AAA is
observed. This lowering of NAH stretching frequency in 2CAAA
than that of AAA shows the presence of strong intramolecular
hydrogen bonding (N11AH12ꢃ ꢃ ꢃO19) due to the chlorine atom
connected at the ortho position. This intramolecular hydrogen
bonding is considered to be the predominant effect than the steric
and polar factors of chlorine.
.
Amide group vibrations
The characteristic vibrations of the amide (ACONHA) group of
AAA, 2CAAA and 2MAAA are analysed and the comparison of the
amide (ACONHA) group vibrations are presented in Table 11.
The C@O stretching (amide-I band) is found at 1663, 1678 and
1673 cmꢂ1 in IR spectrum of AAA, 2CAAA and 2MAAA, respectively.
The comparison of the wavenumber of C@O stretching mode in
2CAAA and 2MAAA with that of AAA molecule reveals that the
substitution of methyl and chloro group in the phenyl ring does
not makes the molecule effectively compete with the carbonyl
group and does not show significant variation from that of the
parent compound acetoacetanilide [45]. The blue shift of acetyl
carbonyl stretching 35–50 cmꢂ1 in IR than amide carbonyl stretch-
ing is due to the electron donating methyl group. The competition
between the delocalisation of the lone pair present in the amide
nitrogen towards carbonyl group and the aromatic ring also
responsible for the blue shift in acetyl carbonyl stretching
frequencies.
The strong vibrations observed at 1545 and 1547 cmꢂ1 in IR and
Raman spectra are ascribed to the amide-II band, the NAH in-plane
bending of AAA. The very strong vibrations observed at 1544 and
1537 cmꢂ1 in IR and Raman spectra are ascribed to the amide-II
band of 2CAAA. The steric effect due to ortho methyl group signif-
icantly operating on the NAH in-plane bending properties. The

Table 8
The observed FTIR, FT-Raman and calculated frequencies by B3LYP method with 6-311++Gꢁꢁ and cc-pVTZ basis sets along with their relative intensities and probable assignments of acetoacetanilidea.
Observed
B3LYP/6-311++Gꢁꢁ
Depolarisation
ratio
B3LYP/cc-pVTZ
Depolarisation
ratio
Assignment
wavenumber
(cmꢂ1
FTIR
)
FTR
Unscaled
Scaled
IR intensity Raman
intensity
Unscaled
Scaled
IR intensity Raman
intensity
(cmꢂ1
)
(cmꢂ1
)
(cmꢂ1
)
(cmꢂ1
)
3294 m
3138 w
3086 w
3072 w
3067 w
3046 w
3480
3240
3191
3177
3167
3157
3144
3113
3084
3296
3140
3088
3074
3069
3048
2956
2929
2901
2855
2838
1714
1662
1619
1603
1547
1499
1446
1415
1434
1410
1363
1343
1325
1309
1239
1179
1167
1161
1155
1143
1074
1018
1027
994
970
975
963
905
870
858
754
748
742
692
687
684
637
561
527
227.96
4.03
17.23
21.36
1.15
6.55
8.14
4.39
4.96
63.81
17.05
100.00
26.13
38.17
13.43
28.34
25.06
22.66
78.24
34.47
0.95
18.29
17.77
41.99
28.33
5.22
1.97
3.12
3.36
3.48
0.47
1.53
11.43
10.07
27.90
5.18
2.00
5.84
2.00
1.57
0.71
6.74
1.03
21.03
0.10
0.30
0.04
0.09
0.02
0.80
4.11
0.13
1.71
0.20
0.16
0.13
0.74
0.57
0.62
0.63
0.31
0.71
0.01
0.16
0.14
0.18
0.57
0.42
0.38
0.33
0.44
0.75
0.65
0.72
0.75
0.53
0.21
0.31
0.25
0.25
0.20
0.19
0.73
0.32
0.20
0.05
0.64
0.10
0.44
0.73
0.70
0.47
0.33
0.20
0.19
0.27
0.13
0.75
0.33
0.37
0.48
0.71
0.12
3478
3245
3192
3179
3169
3159
3144
3114
3084
3031
3017
1771
1749
1648
1642
1590
1534
1482
1476
1463
1441
1392
1363
1349
1337
1278
1233
1205
1203
1184
1180
1113
1054
1046
1020
1010
995
3298
3142
3090
3076
3071
3050
2958
2931
2903
2857
2840
1716
1664
1621
1605
1549
1501
1448
1417
1436
1412
1365
1345
1327
1311
1240
1180
1168
1162
1156
1144
1076
1023
1029
996
981
977
965
907
872
861
756
750
744
694
689
686
639
566
528
239.13
3.94
19.25
23.17
1.21
6.76
8.09
4.79
4.87
0.76
0.91
275.63
132.60
0.86
198.41
369.73
68.99
54.00
10.00
16.44
21.20
54.38
3.31
24.25
87.47
85.97
80.61
9.46
14.27
3.86
39.69
12.37
2.43
7.00
0.39
0.71
22.12
0.06
58.53
16.29
100.00
25.99
38.63
12.69
27.88
25.75
22.54
67.26
32.72
0.43
13.22
29.34
19.63
24.19
4.77
2.28
2.73
3.31
3.60
0.67
0.90
12.27
7.18
22.61
4.35
3.43
2.69
2.23
1.20
0.70
5.04
0.86
17.63
0.14
0.27
0.03
0.06
0.10
0.56
3.58
0.43
1.53
0.21
0.19
0.14
0.74
0.57
0.63
0.63
0.30
0.71
0.01
0.16
0.27
0.20
0.49
0.39
0.38
0.32
0.52
0.75
0.66
0.69
0.73
0.66
0.24
0.36
0.28
0.27
0.17
0.25
0.72
0.35
0.25
0.09
0.73
0.13
0.50
0.57
0.75
0.74
0.75
0.28
0.20
0.38
0.13
0.65
0.47
0.49
0.75
0.70
0.12
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
NAH
CAH
CAH
CAH
CAH
CAH
aCH3
aCH2
aCH3
sCH3
sCH2
C@O(keto)
C@O(anilide)
CC
3069 m
3059 m
2954 vw 2954 w
2921 vw 2927 m
2853 vw 2863 vw 3028
3017
0.79
1.01
1714 s
1663 vs
1619 w
1600 s
1545 s
1499 m
1446 s
1415 w
1727 vw 1765
289.48
177.96
19.40
208.53
358.91
65.50
43.82
16.68
17.34
23.49
59.38
1.25
21.94
89.40
92.53
72.90
16.95
7.48
1662 m
1742
1644
1640
1589
1603 vs
1547 w
CC
bNAH
m
m
daCH3
daCH3
dCH2
dsCH3
m
x
m
m
1501 vw 1527
CC
CC
1451 w
1414 w
1475
1474
1463
1441
1391
1357
1350
1337
1275
1231
1203
1201
1182
1179
1110
1051
1044
1014
1001
994
980
952
921
904
857
848
829
771
761
717
706
632
1410 m
1363 m
1343 m
1329 w
1315 w
1238 w
1178 w
1167 m
1161 m
1155 w
1143 w
1075 vw
1344 m
1325 w
1309 m
1239 m
1179 w
CAN
CH2
CC
NAC
s
CH2
bCH
CC
bCAH
CH3
1161 w
m
6.47
38.59
13.82
3.47
7.41
0.36
0.65
20.81
0.07
3.54
8.65
3.49
3.27
0.88
3.78
55.51
68.96
3.14
21.66
0.60
x
bCAH
bCAH
qCH3
bCCC (TB)
1028 vw 1034 w
995 vw
1000 s
bCAH
976 vw
m
CC
CH3
CAH
bC@O(anilide)
qCH2
964 vw
906 w
864 vw
983
952
927
905
859
853
830
776
764
719
711
635
s
c
3.50
6.75
3.54
3.34
0.61
3.70
39.69
67.71
3.55
17.22
0.57
871 w
755 w
754 m
749 m
743 m
693 w
688 m
685 m
636 w
m
m
CC
CC
bC@O(keto)
0.45
0.61
0.79
0.02
1.84
1.44
0.15
0.33
0.66
0.12
1.66
1.53
c
c
c
c
c
c
NAH
CAH
CAH
CAH
CAH
C@O(anilide)
638 m
528 w
528 vw
608
4.89
609
4.06
(continued on next page)

168
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
NAH in-plane bending of 2MAAA are ascribed to the strong vibra-
tions observed in the IR and Raman spectra at 1597 and 1590 cmꢂ1
.
A blue shift of 45–50 cmꢂ1 is observed in the amide-II bands of
2MAAA than AAA.
The vibrational modes observed at 1343, 1339 and 1340 cmꢂ1
in IR spectra are ascribed to the amide-III band, the CAN stretching
mode of AAA, 2CAAA and 2MAAA, respectively. The spectral data
indicates that no appreciable rise in CAN stretching frequencies
due to the influence of the methyl and chloro groups. The amide-
IV, C@O in-plane bending vibration of AAA is found at 864 and
871 cmꢂ1 in the IR and Raman spectra. In 2CAAA compound, this
mode is observed at 836 and 847 cmꢂ1 in the IR and Raman spec-
tra. The amide-IV band of 2MAAA is assigned at 834 and 842 cmꢂ1
in the IR and Raman spectra. There is a red shift (ꢆ30 cmꢂ1) in the
C@O in-plane bending frequencies of 2CAAA and 2MAAA than that
of AAA are observed.
The amide-V, the NAH out of plane bending mode of AAA,
2CAAA and 2MAAA are found at 693, 758 and 717 cmꢂ1 in the IR
spectrum. The substituent effect of chlorine plays significantly
and the blue shift in o-substituted compounds than the parent in
the amide-V vibration is observed. The C@O out of plane bending
mode (amide-VI) of AAA is observed at 517 cmꢂ1 in IR spectra.
The C@O out of plane bending mode of 2CAAA are observed at
593 and 595 cmꢂ1 in IR and Raman spectra. The C@O out of plane
bending of 2MAAA are assigned at 680 and 689 cmꢂ1 in IR and Ra-
man spectra, respectively. A blue shift of amide-VI, C@O out of
plane bending modes of 2MAAA and 2CAAA than AAA is observed.
Methyl group vibrations
The asymmetric and symmetric stretching modes of ACH3
group normally appear at about 2965 and 2880 cmꢂ1 [50]. The
symmetric stretching,
2853 and 2863 cmꢂ1 in the infrared and Raman spectra of AAA.
The asymmetric stretching, a(CH3) frequencies are observed at
2954 cmꢂ1 in AAA. The symmetric stretching,
s(CH3) frequencies
are observed at 2883 and 2890 cmꢂ1 in the infrared and Raman
spectra of 2CAAA. The asymmetric stretching, a(CH3) frequencies
of 2CAAA are established at 2923 and 2926 cmꢂ1 in the infrared
ms(CH3) frequencies are established at
m
m
m
and Raman spectra. The symmetric stretching, ms(CH3) frequencies
are assigned to the wavenumber at 2871 and 2874 cmꢂ1 in the
infrared and Raman spectra of 2MAAA. The asymmetric stretching,
m
a(CH3) frequencies are attributed to 2980, 2918, 2898 and 2984,
2921, 2901 cmꢂ1 in the infrared and Raman spectra of 2MAAA.
The asymmetric methyl deformation modes da(CH3) of AAA are ob-
served at 1415 and 1414 cmꢂ1 in IR and Raman spectra. The sym-
metrical methyl deformation modes, ds(CH3) of AAA are observed
at 1363 cmꢂ1 in IR spectrum. In 2CAAA, the asymmetrical methyl
deformation modes, da(CH3) are observed at 1449, 1431 and
1450 cmꢂ1 in IR and Raman spectra. The symmetrical methyl
deformation modes, ds(CH3) of 2CAAA are assigned to 1366 and
1368 cmꢂ1 in IR and Raman spectra. The asymmetrical methyl
deformation modes, da(CH3) of 2MAAA are observed at 1486,
1461, 1444, 1430 and 1469, 1451 cmꢂ1 in IR and Raman spectra.
The symmetrical methyl deformation modes, ds(CH3) of 2MAAA
are attributed to 1372, 1365 and 1373, 1366 cmꢂ1 in IR and Raman
spectra. The assignment of the bands at 1143 and 1121 cmꢂ1 in the
infrared spectrum are assigned to the methyl wagging mode of the
compounds AAA and 2MAAA, respectively. The band at 1131 cmꢂ1
in the Raman spectrum is assigned to the methyl wagging mode of
2CAAA. The methyl twisting mode of the compounds AAA, 2CAAA
and 2MAAA are attributed to the bands at 964, 952 and 944 cmꢂ1
,
respectively in the infrared spectra. The rocking mode of the
methyl group of AAA is observed at 1028 and 1034 cmꢂ1 in the
infrared and Raman spectra, respectively. The corresponding mode
of the compound 2CAAA is seen at 1027 and 1035 cmꢂ1 in the

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
169
Table 9
The observed FTIR, FT-Raman and calculated frequencies by B3LYP method with 6-311++Gꢁꢁ and cc-pVTZ basis sets along with their relative intensities and probable assignments
of 2-chloroacetoacetanilidea.
Observed
B3LYP/6-311++Gꢁꢁ
Depolarisation
ratio
B3LYP/cc-pVTZ
Depolarisation
ratio
Assignment
wavenumber
(cmꢂ1
FTIR
)
FTR
Unscaled
Scaled
IR
Raman
Unscaled
Scaled
IR
Raman
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
3206 m
3118 w
3080 w 3080 vw 3203
3069 w 3072 vw 3189
3004 w
2923 w 2926 vw 3144
2888 w
2883 w
3457
3244
3203
3115
3077
3058
3001
2920
2895
2864
2858
2850
1708
190.69
7.85
5.48
11.46
2.75
7.59
4.41
5.12
0.93
0.65
73.35
25.08
86.79
63.86
29.21
34.08
30.64
28.67
100.00
36.88
2.63
0.19
0.16
0.15
0.40
0.71
0.63
0.32
0.71
0.02
0.17
0.21
3459
3249
3205
3191
3176
3144
3119
3082
3030
3019
1776
3204
3116
3078
3059
3002
2921
2896
2864
2881
2851
1709
187.19
7.70
6.32
12.72
3.11
7.59
4.83
5.00
0.89
0.56
76.15
27.56
97.89
75.32
34.25
38.86
36.17
33.06
100.00
41.13
2.18
0.20
0.19
0.17
0.39
0.70
0.63
0.31
0.72
0.02
0.18
0.31
m
m
m
m
m
m
m
m
m
m
m
NAH
CAH
CAH
CAH
CAH
aCH3
aCH2
aCH3
sCH3
3174
2903 w 3116
3083
2890 w 3028
3019
sCH2
C@O(keto)
1710
vs
1772
227.17
207.91
1678 s
1598
vs
1674 w 1744
1597 vs 1634
1676
1595
211.39
145.50
21.70
71.40
0.18
0.42
1751
1636
1677
1596
176.61
102.54
17.88
68.34
0.20
0.44
m
m
C@O(anilide)
CC
1594
vs
1544
vs
1593 vs 1622
1537 m 1574
1591
1535
117.53
425.78
8.22
0.75
0.43
1623
1574
1592
1536
115.57
458.68
5.52
0.70
0.43
m
CC
17.50
17.79
bNAH
1470 m 1474 vw 1498
1449 w 1450 vw 1474
1468
1447
1440
1429
20.44
11.44
79.49
17.16
6.63
3.04
5.90
4.02
0.39
0.73
0.40
0.64
1503
1475
1474
1463
1469
1448
1441
1430
16.54
33.91
61.58
16.01
7.03
2.47
6.74
4.59
0.34
0.51
0.61
0.66
m
CC
daCH3
CC
1442 s
1431
1469
1462
m
daCH3
vw
1372 s
1366 s
1339 w
1313 m
1281 w
1264 m
1231 m
1157 m
1150 m
1444
1368 w 1390
1349
1312 m 1326
1282 m 1310
1257 m 1267
1235
1170 m 1202
1164 m 1186
1131 vw 1178
1152
1370
1364
1337
1310
1279
1255
1229
1168
1148
1129
1078
1049
1035
1025
989
950
929
925
876
845
829
802
760
756
717
706
664
598
591
535
526
462
438
430
379
363
288
259
195
182
154
101
79
25.67
59.09
20.04
107.76
18.82
49.59
93.05
36.26
1.22
38.41
0.59
8.37
52.78
6.70
0.94
17.41
3.42
2.90
4.29
1.21
3.25
3.49
24.10
102.36
3.97
4.20
0.53
8.12
21.51
14.19
18.49
3.12
1.31
6.50
1.65
4.15
5.03
15.36
1.06
0.04
2.37
0.04
0.29
0.58
0.01
4.82
2.32
0.21
0.88
0.65
0.21
2.69
1.99
1.90
2.22
2.02
0.70
0.08
1.32
1.65
2.26
0.83
0.60
1.13
0.34
0.62
0.12
0.14
0.95
0.18
0.73
0.75
0.22
0.30
0.29
0.22
0.42
0.42
0.41
0.40
0.08
0.04
0.10
0.61
0.74
0.30
0.73
0.12
0.28
0.70
0.21
0.11
0.54
0.51
0.29
0.68
0.23
0.25
0.42
0.35
0.30
0.37
0.56
0.27
0.12
0.39
0.71
0.66
0.15
0.75
0.75
0.75
0.69
0.74
0.74
1445
1391
1348
1326
1313
1269
1236
1204
1188
1178
1154
1075
1056
1047
1008
996
968
956
908
1371
1365
1338
1311
1280
1256
1230
1169
1149
1130
1079
1050
1036
1026
990
951
939
927
881
847
833
805
762
758
721
708
666
600
593
537
530
464
443
433
381
365
292
261
197
184
158
103
81
23.81
54.03
21.25
114.48
9.88
40.73
104.81
38.23
1.08
35.29
0.61
8.45
45.28
6.28
0.84
19.36
2.90
3.08
4.88
0.69
2.93
3.48
45.99
64.27
2.80
5.05
0.89
10.76
20.90
10.40
17.92
3.24
1.30
7.06
1.59
4.50
3.95
16.00
1.03
0.10
2.36
0.04
0.38
0.54
0.27
5.03
2.43
0.06
0.72
0.68
0.71
2.55
2.26
1.74
1.64
2.88
0.86
0.10
1.32
1.73
2.23
0.91
0.72
1.26
0.40
0.77
0.08
0.19
1.38
0.20
0.70
0.73
0.25
0.32
0.35
0.23
0.45
0.37
0.46
0.40
0.10
0.08
0.14
0.68
0.74
0.25
0.75
0.16
0.37
0.74
0.22
0.11
0.67
0.66
0.30
0.64
0.29
0.22
0.50
0.41
0.33
0.30
0.67
0.32
0.14
0.40
0.69
0.73
0.14
0.75
0.74
0.72
0.71
0.75
0.74
dCH2
dsCH3
m
x
CAN
CH2
m
m
m
CC
CC
NAC6H5
s
CH2
bCAH
CH3
x
1080 m
1051 m
1037 s
1027 w
991 w
bCAH
bCAH
bCAH
1072
1038 vs 1051
1035 vs 1045
998
q
CH3
bCCC(TB)
CH3
952 w
995
960
956
905
s
c
m
CAH
CC
qCH2
836 w
847 vw
769 vw
879
857
829
766
761
741
730
681
614
583
549
544
472
454
445
393
376
299
281
243
190
161
147
104
79
892
859
830
bC@O(anilide)
m
m
CC
CC
762 s
758 w
772
759
743
739
683
615
584
551
546
474
457
446
393
376
301
bC@O(keto)
c
c
m
c
c
c
NAH
CAH
CACl
CAH
CAH
C@O(anilide)
708 s
712 vw
669 vs
0.69
14.65
6.74
0.59
13.66
5.75
666 w
600 w
593 m
537 m
595 vw
539 w
8.61
8.09
16.24
16.92
2.73
5.55
2.19
6.63
1.52
3.00
1.28
3.05
7.84
2.51
0.56
3.33
2.74
10.07
12.91
22.36
3.00
4.84
2.13
6.67
1.56
2.76
1.28
2.91
7.57
2.80
0.55
3.24
2.53
8.73
bCAN
bNAC6H5
464 vw
c
c
c
CAN
NAC6H5
C@O(keto)
bCCC
bCACl
bCCC
bCCC
bCCH3
261 w
197 m
283
243
190
163
148
104
c
c
c
c
c
c
CCH3
CCC
CACl
CCC
CCC
CCC
103 w
81w
75
60
79
64
77
62
64
(continued on next page)

170
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Table 9 (continued)
Observed
B3LYP/6-311++Gꢁꢁ
Depolarisation
ratio
B3LYP/cc-pVTZ
Depolarisation
ratio
Assignment
wavenumber
(cmꢂ1
FTIR
)
FTR
Unscaled
Scaled
IR
Raman
Unscaled
Scaled
IR
Raman
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
36
22
34
20
1.45
0.60
0.17
0.70
0.73
0.75
35
22
34
21
1.34
0.64
0.18
0.94
0.73
0.75
CH3torsion
Lattice
vibration
a
m
– stretching; b – in-plane bending; d – deformation;
q
– rocking; c – out of plane bending; x – wagging; s – twisting and TB-trigonal bending.
Table 10
The observed FTIR, FT-Raman and calculated frequencies by B3LYP method with 6-311++Gꢁꢁ and cc-pVTZ basis sets along with their relative intensities and probable assignments
of 2-methylacetoacetanilide.a
Observed
B3LYP/6-311++Gꢁꢁ
Depolarisation
ratio
B3LYP/cc-pVTZ
Depolarisation
ratio
Assignment
wavenumber
(cmꢂ1
FTIR
)
FTR
Unscaled
Scaled
IR
Raman
Unscaled
Scaled
IR
Raman
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
3271 m
3121 w
3083
vw
3502
3243
3187
3264
3115
3077
183.65
5.03
22.33
60.17
20.22
100.00
0.18
0.16
0.16
3502
3247
3189
3265
3116
3078
190.30
4.98
24.56
53.58
19.26
100.00
0.20
0.19
0.17
m
m
m
NAH
CAH
CAH
3049
vw
3053 w 3171
3158
3043
15.21
36.28
0.74
3173
3044
15.99
35.80
0.74
m
CAH
3026
2979
2939
2948
2916
2896
2869
2860
2859
1708
6.81
8.20
4.59
18.45
4.86
13.61
0.80
0.95
21.61
287.26
30.91
30.35
27.44
26.58
25.47
25.83
88.74
35.45
76.09
1.28
0.49
0.63
0.32
0.60
0.71
0.72
0.02
0.17
0.03
0.16
3160
3144
3119
3109
3083
3059
3030
3019
3017
1770
3024
2979
2939
2928
2916
2896
2869
2860
2846
1706
7.10
8.10
4.97
17.46
4.75
14.05
0.74
0.94
20.89
278.52
29.58
29.38
27.93
25.05
25.12
24.00
74.93
35.10
67.10
0.69
0.50
0.64
0.31
0.60
0.71
0.70
0.02
0.16
0.03
0.31
m
m
m
m
m
m
m
m
m
m
CAH
aCH3(Ac)
aCH2
aCH3
aCH3(Ac)
aCH3
sCH3(Ac)
sCH2
sCH3
2980 w 2984 w 3144
2944 w
3117
3108
2918 w 2921 m 3083
2898 w 2901 m 3060
2871 w 2874 w 3028
2856 w 2865 w 3019
3015
1708
vs
1765
C@O(keto)
1673 s
1612 s
1597 s
1550
vs
1670 m 1743
1613 w 1650
1673
1612
1590
1545
175.90
45.85
187.72
336.71
20.79
13.02
54.16
16.26
0.19
0.74
0.41
0.44
1750
1653
1632
1587
1671
1610
1588
1543
128.59
31.87
172.66
351.03
15.19
12.29
40.84
14.21
0.21
0.72
0.39
0.44
m
m
C@O(anilide)
CC
1590 s
1630
bNAH
m
1545 m 1585
CC
1491 m 1492 w 1519
1492
1487
1462
38.18
60.55
30.81
7.62
3.35
3.37
0.38
0.75
0.75
1523
1498
1494
1489
1484
1459
32.03
94.09
9.16
6.94
3.40
2.97
0.34
0.72
0.75
m
CC
1486 m
1461 s
1494
1493
daCH3
daCH3
1469
vw
1444 w 1451
vw
1476
1445
10.37
3.82
0.29
1481
1442
5.93
2.88
0.32
daCH3 (Ac)
1430 w
1380 s
1372 s
1474
1384 w 1462
1373 w 1444
1431
1385
1374
1367
1341
1319
12.11
16.62
23.94
2.83
58.89
16.51
2.81
3.50
3.78
3.65
0.52
0.75
0.65
0.72
0.53
0.75
0.20
1475
1463
1444
1423
1392
1348
1428
1382
1371
1364
1338
1316
9.35
16.06
21.62
2.40
54.02
17.75
2.89
3.49
3.88
3.37
0.75
0.75
0.66
0.69
0.50
0.73
0.22
daCH3 (Ac)
dCH2
dsCH3
1365 m 1366 w 1420
dsCH3 (Ac)
1340 w
1318 m 1319
vs
1390
1349
m
x
CAN
CH2
11.89
12.06
1296 w
1335
1320
1277
1298
1282
1269
1233
1196
1170
1152
1124
1104
1052
1042
1031
993
988
968
950
947
883
845
56.46
28.79
104.30
80.49
0.48
28.60
1.09
36.83
3.48
13.04
1.65
6.96
1.84
0.68
8.49
5.56
40.66
7.20
2.33
1.15
4.29
1.22
1.71
12.77
0.06
1.07
0.86
0.10
2.42
0.04
0.97
0.24
0.03
0.32
0.23
0.22
0.27
0.11
0.53
0.58
0.40
0.09
0.08
0.65
0.69
0.33
0.45
0.18
0.70
0.09
0.63
0.73
1335
1325
1279
1232
1213
1203
1188
1179
1140
1076
1062
1046
1012
1004
996
1295
1269
1266
1230
1193
1167
1131
1121
1094
1048
1038
1027
989
984
962
948
943
877
841
50.27
35.85
99.82
87.36
1.19
26.58
0.80
35.74
2.69
11.31
1.43
6.64
1.85
0.56
5.27
4.76
31.79
6.28
1.75
1.00
4.41
0.99
1.52
9.94
0.08
0.94
0.59
0.10
2.22
0.01
0.95
0.17
0.23
0.38
0.26
0.26
0.30
0.17
0.46
0.60
0.40
0.09
0.12
0.75
0.74
0.43
0.75
0.15
0.75
0.11
0.73
0.75
m
m
m
m
m
CC
CC
CC
NAC6H5
CC
1267 m 1268 s
1231 w 1236 w 1231
1194 w 1211
1158 m 1168 m 1202
1186
1121 w 1122 w 1179
1136
1049 m 1062 s
1039 w
1028 w
994 w
985 w
sCH2
bCAH
x
x
bCAH
bCAH
CH3
CH3
1073
1058
1044
1009
996
995
957
954
907
q
CH3
bCCC(TB)
CH3(Ac)
CH3
bCAH
CH3(Ac)
CH2
bC@O(anilide)
990 w
q
s
24.87
2.88
4.36
3.67
1.29
26.07
2.25
4.40
3.87
0.98
961
954
909
890
944 w
834 w
s
q
842 w
883

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
171
Table 10 (continued)
Observed
B3LYP/6-311++Gꢁꢁ
Depolarisation
ratio
B3LYP/cc-pVTZ
Depolarisation
ratio
Assignment
wavenumber
(cmꢂ1
FTIR
)
FTR
Unscaled
Scaled
IR
Raman
Unscaled
Scaled
IR
Raman
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
(cmꢂ1
)
(cmꢂ1
)
intensity intensity
856
829
803
769
741
734
703
616
584
565
545
518
474
453
428
381
308
288
270
208
182
178
152
111
77
833
801
772
754
721
693
606
599
570
553
517
507
465
457
406
375
314
288
218
207
151
140
132
114
81
2.07
3.13
0.59
54.11
36.68
30.14
2.43
3.88
4.38
23.82
1.95
16.12
2.48
5.31
2.05
0.56
3.50
2.09
1.41
9.60
2.36
0.74
0.33
2.56
3.09
10.68
1.30
0.41
2.64
2.17
6.07
0.36
0.58
0.20
2.20
1.82
0.99
5.62
0.17
0.74
0.68
0.06
0.27
1.14
0.80
0.44
1.20
0.25
0.65
0.03
0.09
0.05
0.75
0.15
0.17
0.73
0.42
0.11
0.06
0.75
0.37
0.55
0.23
0.39
0.61
0.23
0.74
0.39
0.39
0.36
0.30
0.55
0.75
0.69
0.12
0.48
0.74
0.13
0.75
0.59
0.75
0.74
0.73
0.75
858
830
805
775
747
741
705
617
587
567
550
519
475
456
430
381
310
290
271
207
184
182
156
112
79
834
797
768
750
717
689
602
595
566
548
512
502
453
452
401
369
309
283
213
202
146
135
127
110
78
1.81
3.33
0.65
41.66
36.81
25.14
2.50
3.11
3.71
24.51
1.93
17.00
2.64
4.44
2.17
0.51
3.24
2.16
1.46
9.53
2.27
0.74
0.23
2.46
2.53
9.52
1.28
0.40
2.33
1.85
5.28
0.05
0.40
0.16
1.79
1.65
0.81
4.99
0.09
0.64
0.72
0.09
0.26
0.98
0.74
0.66
1.08
0.24
0.60
0.04
0.05
0.06
0.95
0.10
0.21
0.87
0.40
0.12
0.08
0.66
0.46
0.60
0.32
0.34
0.70
0.26
0.66
0.45
0.32
0.68
0.28
0.58
0.74
0.67
0.11
0.50
0.73
0.34
0.73
0.55
0.75
0.74
0.73
0.75
m
m
c
CC
CC
CAH
797 s
774 w
768 s
750 m
717 w
bC@O(keto)
714 w
680 vw 689 w
602 w
c
c
c
c
c
NAH
C@O(anilide)
CAH
CAH
CAH
595 w
560 m
598 w
566 m
bCCC
501 w
512 w
bCAN
bNC6H5
bCCC
c
c
c
bCCC
bCACH3
bCACH3
c
c
c
c
c
c
452 w
401 w
CAN
C@O(keto)
NAC6H5
308 w
282 w
212 w
201 m
145 w
134 w
126 m
CACH3
CACH3
CCC
CCC
CCC
CCC
66
36
22
71
42
28
67
37
23
66
37
23
CH3 Torsion
CH3 Torsion
Lattice
vibration
a
m
– stretching; b – in-plane bending; d – deformation; q – rocking; c – out of plane bending; x–wagging; s–twisting; Ac-acetyl and TB-trigonal bending.
Table 11
Comparison of FTIR and FT-Raman (FTR) amide (ACONHA) group vibrations of acetoacetanilide (AAA), 2-chloroacetoacetanilide (2CAAA) and 2-methylacetoacetanilide (2MAAA).
Compound name
mC@O
bNAH
mCAN
bC@O
cNAH
cC@O
mNAH
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
AAA
2CAAA
2MAAA
1663
1678
1673
1662
1674
1670
1545
1544
1590
1547
1537
1597
1343
1339
1340
1344
864
836
834
871
847
842
693
758
717
528
593
680
528
595
689
3294
3206
3271
–
–
–
–
–
714
–
–
infrared and Raman spectra, respectively. The methyl rocking
mode of 2MAAA is attributed to the bands observed at 1028 and
985 cmꢂ1 in the infrared spectrum. These assignments are agreed
well with the reported literatures [51,52].
ging, twisting and rocking modes of AAA, 2CAAA and 2MAAA are
all given in the Tables 8–10.
CACl vibrations
The CACl absorption is observed in the broad region between
850 and 550 cmꢂ1. The strong band in IR at 708 cmꢂ1 having very
weak Raman counterpart at 712 cmꢂ1 is assigned to the CACl
stretching mode of 2CAAA. The in-plane CACl deformation vibra-
tions of 2CAAA is calculated at 363 cmꢂ1 by B3LYP/6-311++Gꢁꢁ
method. The out of plane CACl mode is assigned and given in the
Table 9. These assignments are in good agreement with the litera-
ture values [53–55].
Methylene group vibrations
The asymmetric and symmetric methylene stretching vibra-
tions normally occur at 2926 and 2853 cmꢂ1 [49]. The symmetric
stretching,
AAA. The asymmetric stretching,
lished at 2921 and 2927 cmꢂ1 in the infrared and Raman spectra
of AAA. The
s(CH2) frequencies are calculated at 2850 cmꢂ1 of
2CAAA. The asymmetric stretching, a(CH2) frequency is estab-
lished at 2888 and 2903 cmꢂ1 in the infrared and Raman spectra
of 2CAAA. The symmetric stretching, s(CH2) frequency is assigned
a(CH2) fre-
m
s(CH2) frequencies are calculated at 2838 cmꢂ1 of
m
a(CH2) frequencies are estab-
m
m
Scale factors
m
A better agreement between the computed and experimental
frequencies can be obtained by using scale factors. The method
of linear scaling equation is used [56,57] to determine the scaled
wavenumbers. The scaling equations were minimised the residual
separating experimental and theoretically predicted vibrational
frequencies
to 2944 cmꢂ1 in the infrared spectrum of 2MAAA. The
m
quency is attributed to 2856 and 2865 cmꢂ1 in the infrared and Ra-
man spectra of 2MAAA. The methylene deformation modes, d(CH2)
of AAA, 2CAAA and 2MAAA are observed at 1363, 1372 and
1372 cmꢂ1, respectively in IR spectra. The other methylene wag-

172
V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
Fig. 12. The linear regression between the experimental and scaled theoretical
wavenumbers of 2-chloroacetoacetanilide.
Fig. 11. The linear regression between the experimental and scaled theoretical
wavenumbers of acetoacetanilide.
(i) In 2MAAA the adjacent methyl group influence on the rota-
tion of acylamino group. As the steric hindrance increases,
the plane of acylamino group rotates which render the
C1AN11 bond becomes longer by (0.06 Å) than N11AC13
bond.
(ii) The ꢂI effect of nitrogen (N11) reduces the electron density
of the carbon atom C1, thus its NMR signal is observed in the
very downfield at 137.62, 134.58 and 135.66 ppm in the case
of AAA, 2CAAA and 2MAAA, respectively.
N
ꢁ
X
ꢂ
2
D
¼
k
xTi heor
ꢂ
mEi xpt
i
where xiTheo and miExpt are the ith theoretical harmonic frequency
and ith experimental fundamental frequency (in cmꢂ1), respectively
and N is the number of frequencies which leads to minimum RMS
deviation by the relation
rffiffiffiffi
(iii) The acetyl carbonyl carbon atom C18 of AAA, 2CAAA and
2MAAA compounds are significantly observed in the down-
field with chemical shift value 204.41, 204.66 and
205.33 ppm while the amide carbonyl carbon atom C13 of
AAA, 2CAAA and 2MAAA compounds are also observed in
the downfield with chemical shift value of 164.54, 163.86
and 163.89 ppm, respectively. This clearly reveals that acetyl
carbonyl group is highly polar than that of amide carbonyl
group.
(iv) Substitution of electron withdrawing chloro group in the
ring diminished the carbon–carbon stretching frequencies
in the case of 2-chloroacetoacetanilide than AAA and
2MAAA. There is no systematic variation in these stretching
vibrations with the chloro and methyl group substitution in
the ring.
D
RMS ¼
N
The scaling equations y = 1.0018x ꢂ 1.7969 and y = 1.0014x ꢂ
0.2429 were used to calculate the scaled wave numbers in B3LYP
method with 6-311++Gꢁꢁ and cc-pVTZ basis sets of AAA,
respectively. The scaling equations y = 0.9996x ꢂ 1.4826 and y =
0.1526 + 0.9993x were used to calculate the scaled wave numbers
in B3LYP method with 6-311++Gꢁꢁ and cc-pVTZ basis sets of
2CAAA, respectively. The scaling equations y = 6.8043 + 0.9959x
and y = 1.1574 + 0.9980x were used to calculate the scaled wave
numbers with 6-311++Gꢁꢁ and cc-pVTZ basis sets of 2MAAA,
respectively. The correlation diagram for the calculated and the
experimental frequencies of AAA, 2CAAA and 2MAAA are shown
in Figs. 11–13.
(v) The comparison of the wavenumber of C@O stretching in
2CAAA and 2MAAA with that of AAA molecule reveals that
the substitution of methyl and chloro group in the phenyl
ring does not makes the molecule effectively compete
with the carbonyl oxygen of the amide group. It is evident
from the IR and Raman vibrational frequencies of 2CAAA
and 2MAAA, that the C@O stretching frequencies of the
Conclusion
Complete structural, vibrational, NMR and DFT analyses of
acetoacetanilide, 2-chloroacetoacetanilide and 2-methylacetoace-
tanilide were carried out and the following observations are made

V. Arjunan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 154–174
173
compound is shifted to a higher frequency than that of AAA.
The substituent effect of chlorine plays significantly and the
blue shift in o-substituted compounds than the parent in the
amide-V vibration is observed.
(ix) The amide-VI, C@O out of plane bending modes of 2MAAA
and 2CAAA are significantly raised than that of AAA. A blue
shift of amide-VI, C@O out of plane bending modes of
2MAAA and 2CAAA than AAA is observed.
(x) In AAA, 2CAAA and 2MAAA molecules, the nN
?
pꢁCO interac-
tion between the nitrogen lone pair and the amide carbonyl
(C13@O14) antibonding orbital gives strong stabilisation of
64.75, 62.84 and 64.18 kJ molꢂ1, respectively.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.06.003.
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variation
from
that
of
the
parent
compound
acetoacetanilide.
(vi) It is observed that there is no increase in the NAH stretching
frequency of 2MAAA than that of acetoacetanilide. This
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NAH out of plane bending mode of 2-chloroacetoacetanilide

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