Synthesis, structural, vibrational and quantum chemical investigations of N-(2-methylphenyl)-2,2-dichloroacetamide and N-(4-methylphenyl)-2,2-dichloroacetamide

Article abstract of DOI:10.1016/j.saa.2009.07.008

N-(2-Methylphenyl)-2,2-dichloroacetamide (2MPA) and N-(4-methylphenyl)-2,2-dichloroacetamide (4MPA) of the configuration X_yC₆H_5-y-NHCO-CHCl₂ (where, X = CH₃ and y = 1) were synthesised and an extensiv

Full text of DOI:10.1016/j.saa.2009.07.008

Spectrochimica Acta Part A 74 (2009) 607–616
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, structural, vibrational and quantum chemical investigations of
N-(2-methylphenyl)-2,2-dichloroacetamide and
N-(4-methylphenyl)-2,2-dichloroacetamide
V. Arjunana,∗, P. Ravindranb, K. Subhalakshmia, S. Mohanc
a Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Puducherry – 605 008, India
b Department of Chemistry, Mahatma Gandhi Government Arts College, Mahe – 673 311, India
c Centre for Research and Development, PRIST University, Thanjavur – 613 403, India
a r t i c l e i n f o
a b s t r a c t
Article history:
N-(2-Methylphenyl)-2,2-dichloroacetamide (2MPA) and N-(4-methylphenyl)-2,2-dichloroacetamide
(4MPA) of the configuration XyC6H5−y–NHCO–CHCl2 (where, X = CH3 and y = 1) were synthesised and an
extensive spectroscopic investigations have been carried out by recording the Fourier transform infrared
(FTIR) and FT-Raman spectra and subjecting them to normal co-ordinate analysis, in an effort to provide
mixing of the fundamental modes with the help of potential energy distribution (PED). The ab initio and
DFT studies were carried out with 6-311++G(d,p) basis set to determine the structural, thermodynamical
and vibrational characteristics of the compounds and also to understand the steric influence of methyl
group on the characteristic frequencies of amide (–CONH–) group.
Received 22 February 2009
Received in revised form 25 June 2009
Accepted 7 July 2009
Keywords:
FTIR
FT-Raman
N-(Methylphenyl)-2,2-dichloroacetamide
DFT
© 2009 Elsevier B.V. All rights reserved.
Ab initio
1. Introduction
methylformamide [18], o-methylacetanilide [19] and formanilide
[12,13]. The influence by intermolecular hydrogen bonding and
N-Phenylacetamide is an interesting system because the nearly
planar amide group display bond distances, which are close to
those found in polypeptides. Spectroscopic and crystal structural
studies give valuable informations on bond properties. Amides
are of fundamental chemical interest as conjugation between
nitrogen lone-pair electrons and the carbonyl ␲-bond, results in
distinct physical and chemical properties. As a result of conjugation
betweenthecarbonylbond and thenitrogenlonepair, the C–Nbond
in amides possesses considerable double bond character and can
expect restricted rotation about this bond and a planar configura-
tion for the amide group. This planar structure has been confirmed
by measurement with X-rays and the trans-configuration is the
most stable and it has been shown that protein chains involve
this structure [1–9]. According to literature data, three different
conformational forms of the amide group are possible: trans, cis
(planar) and non-planar. Ab initio calculations and the rotational
spectrum of acetanilide confirmed that the planar conformer with
the CH3 group anti to the ring is the most stable [10,11], in agree-
ment with the reports of other experimental investigations [12–15].
The –CO–NH– group adopts a planar ‘peptide-like’ conformation, as
in the case of formamide [16], methyl hydrazinocarboxylate [17], N-
crystal packing on the conformation of the acylamino group relative
to the aromatic ring were discussed [20,21].
Many N-phenylacetamide derivatives exhibit fungicidal, her-
bicidal and pharmacological activities which further stimulated
the recent interest in their chemistry. Anilide herbicides such
as alachlor, acetochlor, metolachlor, pretilachlor and butachlor
are promising weed control agents for a wide variety of eco-
nomically important crops including rice, cotton, potatoes and
corns [22–25]. The choloroacetanilde herbicide alachlor is one
of the most extensively used agro chemical [26,27]. Propanil
(3,4-dichloropropioanilide) is a selective contact anilide herbicide
commonly used for the control of broad leveled and grass weeds.
N-Phenylacetamide is used in medicine under the name antifebrin,
as a febrifuge and it has pain relieving properties [28]. Acetanilide
is an useful intermediate in various reactions of aniline in which it
is desirable to protect the amino group.
Many researches have been carried out the nonlinear
properties of molecular crystals of acetanilide [29–32]. Ab ini-
tio molecular orbital calculations and infrared spectroscopic
data for the frequencies are applied to analyse the group-
ing in a series model aromatic secondary amides: formanilide;
acetanilide; o-methylacetanilide; 2,6-dimethylformanilide, 2,6-
dimethylacetanilide; N-benzylacetamide and N-benzylformamide
[19,33,34]. The temperature dependence of the Raman scattering
from a single crystal of acetanilide and fully deuterated acetanilide
∗
Corresponding author. Tel.: +91 413 2211111; fax: +91 413 2251613.
E-mail address: varjunftir@yahoo.com (V. Arjunan).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.07.008

608
V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
Table 1
Melting point and elemental analysis of the prepared compounds.
Name of the compound
Melting point (◦C)
% found/(calculated)
C
H
N
N-(2-Methylphenyl)-2,2-dichloroacetamide
N-(4-Methylphenyl)-2,2-dichloroacetamide
130
152
49.52(49.57)
49.50(49.57)
4.12 (4.16)
4.17 (4.16)
6.41 (6.42)
6.43 (6.42)
range of 4000–400 cm−1. The spectral resolution was 2 cm−1. The
FT-Raman spectra of these compounds were also recorded with
the same instrument with FRA 106 Raman module. The Raman
in the low frequency (phonon) and C O stretching regions was
studied by Sauvajol et al. [35].
As amides are the simplest model for peptides, and also due to
the fungicidal, herbicidal and several pharmacological activities of
manyacetanilidederivatives, theirexactstructurehasbeenthesub-
ject of many experimental and theoretical studies [19,36–39]. The
vibrational spectroscopic analysis of acetanilide derivatives partic-
ularly the N-(methyl substituted phenyl)-2,2-dichloroacetamides
have not been studied. Thus, in continuation of earlier studies
on N-(chloro substituted phenyl)-2,2-dichloroacetamides [1], we
have prepared N-(2-methylphenyl)- and N-(4-methylphenyl)-2,2-
dichloroacetamides of the configuration XyC6H5−y–NHCO–CHCl2
(where, X = CH3 and y = 1) and an extensive spectroscopic and quan-
tum chemical studies were carried out in an effort to provide
possible explanations for vibrational frequencies and to understand
the effect of methyl group on the characteristic frequencies of amide
group.
spectrum was obtained in the wavenumber range 3500–100 cm−1
.
The light scattering was excited using a low-noise diode pumped
Nd:YAG laser source operating at 1.064 ␮m with 200 mW power. A
special (enhanced) liquid nitrogen cooled germanium detector was
used. The frequencies of all sharp bands are accurate to 2 cm−1
.
3. Computational details
The gradient corrected density functional theory (DFT) [40] with
the three-parameter hybrid functional Becke3 (B3) [41] for the
exchange part and the Lee–Yang–Parr (LYP) correlation function
[42], level of calculations have been carried out in the present
investigation, using 6-311++G(d,p) basis sets with Gaussian-03 [43]
program package, invoking gradient geometry optimisation [44] on
a Pentium-IV/1.6 GHz processor. Following geometry optimisations
with HF and B3LYP method using 6-311++G(d,p) basis sets, the opti-
mised structural parameters were used in the vibrational frequency
calculations to characterise all stationary points as minima. The har-
monic vibrational frequency calculations were carried out for 2MPA
and 4MPA resulting in IR and Raman frequencies together with
intensities and Raman depolarization ratios. The dipole moment
derivatives and polarizability derivatives were computed analyti-
cally. The Raman intensities were computed in the double harmonic
approximation [45], ignoring cubic and higher force constants and
omitting second and higher polarizability derivatives. Owing to
the complexity of the molecule, the potential energy distribution
of the vibrational modes of the compounds are also calculated
through normal coordinate analysis [46–48] using the force con-
stants obtained from the HF and DFT methods utilising the program
of Fuhrer et al. [49]. The force constants were refined by damped
least square fitting technique to achieve a close agreement between
the observed and calculated frequencies.
2. Experimental
The compounds N-(2-methylphenyl)-, and N-(4-methylphenyl)-
2,2-dichloroacetamides were prepared from the respective methy-
laniline, dichloroacetic acid and phosphorus oxychloride based on
the procedure reported [1]. The pure samples of 2-methylaniline,
4-methylaniline, dichloroacetic acid and phosphorus oxychloride
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. The synthesised crude compounds were recrystallised
from ethanol several times. The melting points of the recrystallised
samples were determined. The purity of the compounds were
confirmed by chemical analysis for C, H and N. The compounds pre-
pared, the melting point and elemental analysis of the compounds
are presented in Table 1.
The FTIR spectra of the compounds were recorded in the solid
phase by KBr disc method in a Bruker IFS 66 V spectrometer in the
Fig. 1. Molecular structure and atom numbering of (a) N-(2-methylphenyl)- and (b) N-(4-methylphenyl)-2,2-dichloroacetamides.

V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
609
Computed harmonic frequencies typically overestimate vibra-
tional fundamentals due to basis set truncation and neglect of
electron correlation and mechanical anharmonicity [50]. To com-
pensate these shortcomings and to correlate the experimentally
observed and theoretically computed frequencies for each vibra-
tional modes of the compounds under HF and DFT-B3LYP methods,
scale factors are introduced [51–58]. Initially, all scaling factors have
been kept fixed at a value of 1.0 to produce the pure HF and DFT cal-
culated vibrational frequencies which are given in Tables 4 and 5.
Subsequently, in the HF/6-311++G(d,p) method the empirical scal-
ing factors 0.85, 0.86 and 0.91 for N–H, C O and other vibrations,
respectively, for both 2MPA and 4MPA are used as suggested by
Table 2
Structural parameters calculated for N-(2-methylphenyl)-2,2-dichloroacetamide and N-(4-methylphenyl)-2,2-dichloroacetamide employing HF/6-311++G(d,p) and B3LYP/6-
311++G(d,p) methods.
Structural parameters
N-(2-Methylphenyl)-2,2-dichloroacetamide
N-(4-Methylphenyl)-2,2-dichloroacetamide
N-Phenylacetamide
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
Experimentalb
Internuclear distance (Å)
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
C6–C1
C6–N7
N7–C8
1.386
1.380
1.385
1.385
1.401
1.388
1.416
1.347
1.537
1.189
1.778
1.074
1.513
0.992
1.072
1.086
1.392
1.391
1.393
1.395
1.412
1.399
1.417
1.359
1.542
1.216
1.804
1.083
1.511
1.010
1.083
1.094
1.378
1.392
1.384
1.390
1.384
1.392
1.414
1.345
1.537
1.190
1.778
1.075
1.510
0.994
1.072
1.086
1.387
1.401
1.396
1.395
1.397
1.401
1.415
1.358
1.542
1.216
1.804
1.082
1.509
1.011
1.083
1.094
1.384
1.376
1.391
1.379
1.397
1.391
1.413
1.354
1.495
1.219
C8–C9
C8–O10
aC9–Cl
aC–H (ring)
aC–C (methyl)
N7–H18
C9–H19
aC17–H (methyl)
Bond angle (◦)
C2–C1–C6
C2–C1–H13
C6–C1–H13
C1–C2–C3
C1–C2–H14
C3–C2–H14
C2–C3–C4
C2–C3–H15
C4–C3–H15
C3–C4–C5
C3–C4–H
C5–C4–H
C4–C5–C6
C4–C5–C17
C6–C5–C17
C2–C3–C17
C4–C3–C17
C1–C6–C5
119.806
120.102
120.092
120.599
119.028
120.374
119.140
120.696
120.164
121.759
119.461
118.779
118.252
119.994
121.754
119.719
120.683
119.598
120.551
119.113
120.337
119.330
120.580
120.091
121.715
119.668
118.617
118.113
120.341
121.545
120.567
119.506
119.927
121.256
118.918
119.826
117.350
120.451
119.716
119.833
121.223
119.036
119.741
117.493
122.321
119.543
118.136
119.365
122.262
119.333
118.406
119.301
120.810
121.840
119.141
116.799
124.060
111.093
107.802
115.011
128.619
116.370
128.847
115.310
117.843
107.285
111.526
107.628
111.016
120.878
121.629
119.270
117.159
123.571
111.282
107.602
115.078
128.841
116.081
126.764
115.004
118.232
107.638
111.723
107.287
110.921
120.445
122.416
117.140
111.331
107.544
115.494
128.949
115.556
127.239
115.129
117.632
107.269
111.564
107.601
111.005
120.572
122.195
117.233
111.574
107.283
115.383
129.161
115.457
127.084
114.869
118.048
107.625
111.752
107.256
110.931
C1–C6–N7
C5–C6–N7
aC–C17–H (methyl)
aH–C17–H (methyl)
C6–N7–H18
C6–N7–C8
H18–N7–C8
N7–C8–O10
N7–C8–C9
O10–C8–C9
C8–C9–H19
aC8–C9–Cl
aCl–C9–H
aCl–C9–Cl
Dihedral angle (◦)
C2–C1–C6–N7
C4–C5–C6–N7
C1–C6–N7–H18
C1–C6–N7–C8
C5–C6–N7–H18
C5–C6–N7–C8
C6–N7–C8–O10
C6–N7–C8–C9
H18–N7–C8–O10
−179.997
179.997
179.965
−0.039
−0.033
179.963
0.002
−179.999
179.999
179.987
−0.015
−0.012
179.985
0.004
−179.996
179.996
0.023
−179.964
−179.974
0.039
−0.004
179.996
−179.991
−179.997
179.997
0.033
−179.944
−179.9649
0.057
−0.01
180.0
−180.0
−179.997
−179.993
−179.988
180.0
a
Mean value.
Values taken from Ref. no. [50].
b

610
V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
Table 3
The calculated thermodynamic parameters of N-(2-methylphenyl)-2,2-dichloroacetamide and N-(4-methylphenyl)-2,2-dichloroacetamide employing HF/6-31++G(d,p) and
B3LYP/6-311++G(d,p) methods.
Thermodynamic parameters (298 K)
N-(2-Methylphenyl)-2,2-dichloroacetamide
N-(4-Methylphenyl)-2,2-dichloroacetamide
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
SCF energy (a.u.)
−1394.509
118.216
42.987
114.713
116.438
110.707
−1398.951
111.175
46.064
118.146
109.397
103.199
−1394.511
118.032
43.253
118.808
116.255
110.274
−1398.952
109.840
42.337
107.955
108.062
102.780
Total energy (thermal), Etotal (kcal mol−1
)
Heat capacity at const. volume, Cv (cal mol−1 K−1
)
Entropy, S (cal mol−1 K−1
)
Vibrational energy, Evib (kcal mol−1
)
Zero-point vibrational energy, E0 (kcal mol−1
)
Rotational constants (GHz)
A
B
C
1.158
0.335
0.308
1.132
0.331
0.304
1.498
0.259
0.254
1.459
0.256
0.251
Dipolemoment (Debye)
ꢀx
ꢀy
ꢀz
ꢀtotal
0.772
2.377
0.002
2.50
1.127
2.391
0.001
2.643
1.294
−2.049
0.004
1.724
−2.043
0.008
2.424
2.673
Scott and Radom [59], and Wong [60]. In B3LYP/6-311++G(d,p) level
the correction factors 0.91 for N–H, 0.96 up to 1762 cm−1 and 0.99
for other frequencies of 2MPA while for 4MPA 0.98 is the scale fac-
tor for other vibrations less than 1759 cm−1. The resultant scaled
frequencies are also listed in Tables 4 and 5. These are much closer
to unity and thus the vibrational frequencies calculated by using
the B3LYP functional with 6-311++G(d,p) basis set can be utilised
to eliminate the uncertainties in the fundamental assignments in
infrared and Raman vibrational spectra [61].
of theory are in good agreement with the structural parameters of
N-phenylacetamide [62].
4.3. Vibrational analysis
The FTIR and FT-Raman spectra of N-(2-methylphenyl)-
and N-(4-methylphenyl)-2,2-dichloroacetamides are shown in
Figs. 2 and 3. All the observed wavenumbers are assigned in terms
of fundamentals, overtones and combination bands. The observed
and calculated frequencies by ab initio and DFT methods along
with their relative intensities, probable assignments, depolariza-
tion ratios and potential energy distributions (PED) of 2MPA and
4MPA are summarised in Tables 4 and 5.
4. Results and discussion
4.1. Molecular geometry
4.3.1. Carbon–carbon vibrations
The molecular structure and atom numbering scheme of the
compounds under investigation is shown in Fig. 1. The geometry
of the molecules are considered by possessing CS point group sym-
metry. Under CS symmetry the 60 fundamental vibrations of 2MPA
and 4MPA span the irreducible representations 39Aꢀ + 21Aꢀꢀ. All the
vibrations are active in both IR and Raman.
The carbon–carbon stretching modes of the phenyl group are
expected in the range from 1650 to 1400 cm−1. Benzene has
two degenerate modes at 1596 cm−1 (e2g) and 1485 cm−1 (e1u).
4.2. Structural properties
The steric interaction of methyl substituent on the ring is of great
importance in determining its structural and vibrational properties.
The steric crowding by adjacent substituents on an aromatic ring
may be reduced by the rotation of one of the substituents around
its bond to the aromatic ring. The optimised structural parame-
ters bond lengths and the bond angles for the thermodynamically
preferred geometry of 2MPA and 4MPA at HF and B3LYP levels
with 6-311++G(d,p) basis sets are presented in Table 2 in accor-
dance with the atom numbering scheme of the molecules shown
in Fig. 1(a) and (b). The bond lengths between the amide nitrogen
and the aromatic ring, C6–N7 and between the amide nitrogen and
the carbonyl group, N7–C8 given in Table 2 reflect the changes in
conjugation. The adjacent methyl group influence on the rotation
of acylamino group. As the steric hindrance increases and the plane
of acylamino group rotates, the C6–N7 bond becomes longer and
the N7–C8 bond becomes shorter. The thermodynamic parameters
of the compound has also been computed at HF and B3LYP meth-
ods with 6-311++G(d,p) basis sets and are presented in Table 3.
The calculated SCF energy and entropy of the compounds clearly
indicates that 4MPA is more stable than 2MPA. The bond length
of the compounds 2MPA and 4MPA determined at the DFT level
Fig. 2. FTIR spectrum of (a) N-(2-methylphenyl)-2,2-dichloroacetamide and (b) N-
(4-methylphenyl)-2,2-dichloroacetamide.

Table 4
The observed FTIR, FT-Raman and calculated frequencies using HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) force field along with their relative intensities, probable assignments and potential energy distribution (PED) of
N-(2-methylphenyl)-2,2-dichloroacetamidea.
Species
Observed
HF/6-311++G(d,p) calculated wavenumber
B3LYP/6-311++G(d,p) calculated wavenumber
Depolarization ratio
Assignment
%PED
wavenumber
(cm−1
FTIR
)
FTR
Unscaled (cm−1
)
Scaled (cm−1
)
IR intensity
Raman activity
Unscaled (cm−1
)
Scaled (cm−1
)
IR intensity
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
3250 vs
3110 s
3247 w
3891
3420
3368
3350
3333
3320
3256
3197
3152
1951
1802
1778
1724
1644
1615
1614
1597
1540
1435
1413
1386
1381
1334
1319
1288
1232
1198
1158
1142
1112
1082
1070
1058
981
926
917
866
848
838
798
757
721
603
601
555
525
492
469
450
326
3307
3112
3065
3049
3033
3021
2963
2909
2868
1678
1640
1618
1569
1496
1470
1469
1453
1401
1306
1286
1261
1257
1214
1200
1172
1121
1090
1054
1039
1012
985
974
963
893
843
834
788
772
763
726
689
656
549
547
505
478
448
50.52
2.91
2.37
22.28
18.91
3.65
21.72
22.19
32.24
373.88
51.23
195.35
365.94
27.34
79.16
8.23
43.90
46.73
62.55
200.90
77.06
61.44
62.64
56.45
151.46
30.47
27.71
71.21
4.11
3608
3241
3191
3184
3175
3162
3111
3051
3007
1762
1651
1631
1578
1519
1494
1492
1477
1418
1341
1323
1282
1264
1252
1221
1208
1188
1137
1073
1059
1006
998
972
959
882
867
803
799
770
762
733
674
647
566
565
539
490
451
3283
3111
3063
3057
3048
3036
2987
2929
2887
1692
1634
1615
1562
1504
1479
1477
1462
1404
1328
1310
1269
1251
1239
1209
1196
1176
1126
1062
1048
996
988
962
949
873
858
795
791
762
754
726
667
641
560
559
534
485
38.64
4.31
17.70
1.75
11.76
6.39
0.12
0.20
0.22
0.16
0.73
0.55
0.54
0.75
0.03
0.19
0.74
0.49
0.63
0.52
0.70
0.75
0.07
0.46
0.09
0.12
0.22
0.75
0.16
0.22
0.45
0.43
0.67
0.75
0.07
0.75
0.11
0.75
0.49
0.75
0.23
0.75
0.01
0.75
0.46
0.75
0.75
0.15
0.29
0.75
0.75
0.50
0.75
0.01
0.26
0.75
0.63
0.32
␯NH
␯CH
␯CH
␯C–H(Cl2)
␯CH
94␯
NH
97␯
95␯
93␯
92␯
92␯
95␯
97␯
96␯
95␯
92␯
91␯
CH
CH
CH
CH
CH
CH
CH
CH
3059 vs
3026 s
3065 s
␯CH
3006 vs
3010 vw
2992 s
2923 s
1674 s
13.93
13.53
22.76
328.90
16.55
108.24
284.36
29.00
9.29
92.54
16.10
3.64
60.01
19.93
60.58
11.64
20.57
15.17
1.82
0.04
4.23
11.42
1.68
3.61
0.58
0.43
2.26
1.05
␯aCH3
␯aCH3
␯sCH3
2925 w
1677 vs
1644 s
1611 m
1588 s
␯C
␯C
␯C
O
C
C
C
C
O
C
C
C
1590 vs
1555 s
␤N–H
␯C
90␤NH
89␯
1549 vs
1487 m
7.05
5.54
8.35
2.28
C
C
C
␦aCH3
␯C–C
␦aCH3
␯C–C
␯C–C
␯C–N
␦sCH3
␤C–H(Cl2)
␯N–C6H5
␯C–C
␥C–H(Cl2)
␤C–H
␤C–H
␻CH3
93␦CH
3
87␯
CC
1458 vs
1428 m
1382 m
1341 s
1328 s
1286 m
1450 w
1430 w
1385 w
1350 s
1330 m
1285 vw
1267 s
34.66
1.29
91␦CH
3
4.09
85␯
87␯
88␯
CC
125.45
155.20
25.89
29.17
0.65
2.36
3.08
3.82
1.68
1.12
10.55
0.55
4.36
3.37
15.22
22.52
6.68
5.36
34.55
2.86
0.04
11.35
8.93
0.21
10.55
0.29
3.12
0.09
1.38
0.31
4.80
6.64
21.77
1.21
6.05
0.82
5.41
7.38
8.94
0.34
0.04
2.05
0.21
5.83
3.03
1.95
1.49
2.74
CC
CN
92␦CH
85␤CH3+ 12␤CC
88␯
NC
1247 s
1223 m
89␯
CC
1220 vw
1195 m
1112 w
1085 w
1040 vw
1010 s
79␥CH + 15␥CC
75␤CH + 15␤CCC
77␤CH + 12␤CCC
1115 m
1037 m
69␻
+ 18␥CH
CH
3
␤C–H
␳CH3
71␤CH + 15␤CCC
79ꢁCH + 16␤CH
72␤CH3+ 20␤CCC
76␥CH + 18␥CCC
72␥CH + 21␥CCC
70␥CH + 22␥CCC
68␥CH + 24␥CCC
70␤CCC + 18␤CH
82␤C O + 12␤NH
82␯CCl + 12␤CH
79␥NH + 15␥CO
74␤CCC + 12␤CH
84␯CCl + 10␤CH
79␥C O + 14␥NH
69␤CC + 22␤CH
70␤CCC + 18␤CH
71␤CN + 15␤CO
67␤NC + 19␤CCC
␤C–H
␥C–H
␥C–H
␥C–H
␥C–H
␤CCC
975 s
938 m
873 s
976 w
1.13
1.28
875 w
852 w
858 m
14.99
57.52
34.93
99.29
17.38
1.10
82.55
4.88
6.43
6.47
7.06
50.21
82.92
43.34
3.58
807 vs
769 vs
717 s
800 s
777 m
725 m
␤C O
␯aCCl2
␥N–H
␤CCC
␯sCCl2
␥C O
␤C–C
703 s
667 vs
570 s
543 m
515 vw
3.31
675 vw
560 m
545 w
525 m
94.97
16.11
5.87
22.41
21.52
5.86
6.16
0.59
2.89
0.65
0.74
␤CCC
␤C–N
49.63
21.53
7.27
3.10
3.38
2.05
0.35
3.26
␤N–C6H5
␥C–N
␥N–C6H5
␤C–C(H3)
␦CCl2
446 s
412 w
443 w
410 w
395 vw
332 m
295 w
258 m
446
428
407
296
280
267
72␥CN + 14␥C
O
427
410
297
277
432
411
299
283
69␥NC + 14␥CCC
65␤CC + 21␤CH
80␦CCl + 18␤CH
67␥CCC2 + 22␥CH
68␥CC + 18␥CH
304
298
␥CCC
␥C–C(H3)
271
270
2.22

612
V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
Fig. 3. FT-Raman spectrum of (a) N-(2-methylphenyl)-2,2-dichloroacetamide and
(b) N-(4-methylphenyl)-2,2-dichloroacetamide.
Similarly the frequency of two non-degenerate modes observed
at 1310 cm−1 (b2u) and 995 cm−1 (a1g) in benzene [63], are not
very sensitive to substitution, although heavy halogens and bulky
methyl groups cause undoubtedly slightly alter the frequency [64].
Under CS symmetry, the C C stretching of 2MPA molecule is found
in the IR spectrum at 1644, 1611 and 1549 cm−1 as medium to very
strong bands and strong band at 1555 cm−1 in Raman, while in the
case of 4MPA these vibrations are observed in IR spectra at 1642,
1601 and 1513 cm−1. The corresponding bands in Raman spectrum
are seen at 1611 and 1517 cm−1. The C–C stretching modes of 2MPA
are assigned to the bands observed at 1428, 1382 and 1247 cm−1
in the IR while the respective Raman bands are observed at 1430
and 1385 cm−1. The vibrational frequencies observed in the infrared
spectrum of 4MPA at 1410, 1385 and 1243 cm−1 and at 1409, 1381
and1241 cm−1 intheRamanspectrumareattributedtoC–Cstretch-
ing modes. The in-plane carbon and out of plane bending vibrations
are assigned and presented in Tables 4 and 5. All these assign-
ments are agree well with the reported literature values [65]. The
CCC in-plane bending and out of plane vibrations are described as
mixed modes as there are about 10–20% PED contributions mainly
from C–H in-plane and out of plane bending vibrations, respec-
tively. In 2MPA the ring breathing mode corresponding to the a1g
mode of benzene is determined at 834 cm−1 by HF and 795 cm−1
by B3LYP methods. The ring breathing mode of 4MPA is observed in
the infrared spectrum at 868 cm−1 and in the Raman at 871 cm−1
[66].
4.3.2. C–H vibrations
The aromatic C–H stretching vibrations are normally found
between 3150 and 3000 cm−1. In this region the bands are not
affected appreciably by the nature of substituents. The aromatic
C–H stretching frequencies arise from the modes observed at 3062
(a1g), 3047 (e2g), 3060 (b1u) and 3080 (e1u) cm−1 of benzene and
its derivatives. The C–H present in the benzene ring of 2MPA
gives very strong to strong bands at 3110 and 3026 cm−1 in IR.
The vibrational modes observed at 3109, 3079 and 3040 cm−1 are
assigned to the ring C–H stretching modes of 4MPA. The frequen-
cies at 3059, 3065 and 3061, 3060 cm−1, respectively is attributed
to the C–H stretching of –CHCl2 group. The aromatic C–H in-plane
bending modes of 2MPA and 4MPA corresponding to the benzene

Table 5
The observed FTIR, FT-Raman and calculated frequencies using HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) force field along with their relative intensities, probable assignments and potential energy distribution (PED) of
N-(4-methylphenyl)-2,2-dichloroacetamide.
Species
Observed wavenumber
HF/6-311++G(d,p) calculated wavenumber
B3LYP/6-311++G(d,p) calculated wavenumber
Depolarization ratio
Assignment
% PED
(cm−1
FTIR
)
FTR
Unscaled (cm−1
)
Scaled (cm−1
)
IR intensity
Raman activity
Unscaled (cm−1
)
Scaled (cm−1
)
IR intensity
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
Aꢀ
Aꢀ
Aꢀꢀ
Aꢀꢀ
3240 vs
3109 m
3236 w
3864
3415
3367
3328
3325
3307
3242
3214
3165
1947
1806
1786
1718
1673
1613
1605
1549
1540
1456
1409
1386
1381
1336
1316
1303
1277
1187
1163
1108
1098
1087
1060
1053
943
934
917
914
858
842
778
757
698
677
572
563
492
467
457
408
378
3284
3108
3064
3028
3026
3009
2950
2925
2880
1674
1643
1625
1563
1522
1468
1461
1410
1401
1325
1282
1261
1257
1216
1198
1186
1162
1080
1058
1008
999
989
965
958
858
850
834
832
781
766
708
689
635
616
521
512
448
46.74
1.76
2.34
53.93
45.56
62.36
168.34
50.45
46.29
61.90
91.72
236.19
37.68
125.65
4.45
19.40
5.70
8.10
10.58
0.04
9.38
3595
3241
3183
3169
3165
3151
3103
3071
3023
1759
1655
1636
1568
1544
1495
1487
1438
1414
1346
1338
1274
1259
1252
1234
1216
1208
1148
1061
1036
1008
984
969
950
875
849
821
798
794
763
719
654
647
634
556
517
457
425
3271
3111
3056
3042
3038
3025
2979
2948
2902
1689
1622
1603
1537
1513
1465
1457
1409
1386
1319
1311
1249
1234
1227
1209
1192
1184
1125
1040
1015
988
964
950
931
858
832
805
782
778
748
705
641
634
621
545
507
448
31.09
3.13
1.67
0.14
0.22
0.22
0.17
0.58
0.74
0.75
0.75
0.05
0.20
0.50
0.70
0.38
0.32
0.73
0.75
0.48
0.41
0.19
0.13
0.19
0.75
0.23
0.06
0.16
0.11
0.75
0.75
0.13
0.75
0.44
0.75
0.38
0.75
0.05
0.75
0.75
0.75
0.02
0.75
0.75
0.71
0.68
0.75
0.75
0.16
0.05
0.75
0.55
0.75
0.13
0.52
␯NH
␯CH
␯CH
␯C–H(Cl2)
␯CH
92␯
94␯
NH
CH
3079 w
3060 s
3040 w
91␯
CH
3061 s
8.68
9.08
93␯
CH
25.63
16.37
23.71
26.24
45.98
380.63
33.01
147.81
489.43
47.95
20.46
6.27
18.16
13.17
16.15
16.35
37.27
348.79
5.80
81.14
359.74
42.20
27.23
7.20
32.09
0.07
63.64
6.32
45.26
29.02
21.81
0.59
13.27
0.05
11.83
3.35
3.38
5.68
1.15
2.35
0.89
5.36
17.16
43.38
61.81
5.60
47.76
0.06
0.08
98.23
8.85
31.21
33.87
24.89
1.72
0.19
0.18
90␯
CH
␯CH
92␯
CH
3002 m
2936 vw
2919 vw
1669 vs
1642 w
1601 m
1551 s
3003 s
␯aCH3
␯aCH3
␯sCH3
93␯
CH
95␯
CH
2920 s
1669 s
92␯
CH
␯C
␯C
␯C
O
C
C
95␯
90␯
89␯
C
C
C
O
C
C
1611 s
1546 s
␤N(H
␯C
91␤NH
88␯
1513 s
1517 vw
1475 vw
1450 w
1409 w
1381 w
1340 vs
1308 m
C
C
C
␦aCH3
␦aCH3
␯C(C
␯C(C
␯C(N
␦sCH3
␯C(C
␤C(H(Cl2)
␯N(C6H5
␯C(C
␥C(H(Cl2)
␤C(H
␤C(H
␻CH3
␤C(H
␳CH3
␤C(H
␥C(H
␥C(H
␤CCC
␥C(H
␤C O
␯aCCl2
␥C(H
91␦CH
88␦CH
3
1446 vw
1410 m
1385 m
1348 m
1307 w
3
47.17
4.99
87␯
CC
86␯
CC
64.66
187.87
34.34
30.69
1.43
4.35
0.60
6.16
12.95
2.37
2.78
0.85
1.65
1.90
5.50
31.57
9.22
89␯
CN
90␦CH
3
85␯
CC
1283 vw
1264 m
1243 m
1220 w
1178 w
1284 vw
5.65
83␤CH + 12␤CC
21.72
20.66
10.10
14.34
0.99
0.02
0.34
0.06
2.45
0.16
1.28
0.83
20.86
6.39
0.48
6.24
26.43
1.84
6.21
5.98
1.79
0.43
0.04
6.61
5.39
0.06
0.99
86␯
NC
1241 vs
1215 m
1179 m
87␯
CC
80␥CH + 14␥CC
76␤CH + 14␤CCC
77␤CH + 16␤CCC
1119 vw
1043 vw
70␻
+ 18␥CH
CH
3
73␤CH + 14␤CCC
78␳
1021 vw
980 w
944 vw
+ 16␤CH
CH
981 w
72␤CH3+ 18␤CCC
75␥CH + 14␥CCC
72␥CH + 20␥CCC
76␤CCC + 16␤CH
69␥CH + 22␥CCC
85␤C O + 10␤NH
74␯CCl + 14␤CH
71␥CH + 18␥CCC
70␥NH + 16␥CO
74␤CCC + 12␤CH
74␯CCl + 14␤CH
78␥C O + 12␥NH
67␤CC + 24␤CH
67␤CCC + 18␤CH
75␤CN + 16␤CO
69␤NC + 19␤CCC
912 w
871 vs
5.39
868 w
15.03
13.22
105.30
18.60
46.32
7.77
0.41
86.55
0.29
10.85
1.46
81.76
24.81
1.28
810 vs
792 s
809 m
793 w
745 w
710 w
668 vs
636 w
615 vw
532 w
515 m
490 m
466 w
420 vw
744 m
703 s
␥N(H
␤CCC
␯sCCl2
␥C O
␤C(C
638 m
␤CCC
␤C(N
517 w
491 w
␤N(C6H5
␥C(N
␥N(C6H5
␤C(C(H3)
␦CCl2
425
416
371
344
288
267
417
411
370
342
291
260
72␥CN + 12␥C
O
411 w
358 m
332 s
316 m
260 w
0.65
0.25
0.22
2.36
419
378
349
297
65␥NC + 18␥CCC
66␤CC + 20␤CH
82␦CCl + 18␤CH
65␥CCC2 + 22␥CH
64␥CC + 20␥CH
3.63
1.57
2.74
0.06
1.60
1.18
317
293
␥CCC
␥C(C(H3)
1.45
265

614
V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
degenerate e2g (1178 cm−1) and e1u (1037 cm−1) and two non-
degenerate b2u (1152 cm−1) and a2g (1340 cm−1) vibrations, are
observed in the region 1300–1000 cm−1. The C–H out of plane
bending mode the compounds similar to the b2g (985 cm−1), e2u
(970 cm−1), e1g (850 cm−1) and a2u (671 cm−1) modes of ben-
zene derivatives are observed in the region 1100–600 cm−1 [63]
and are presented in Tables 4 and 5. The aromatic C–H in-plane
and out of plane bending vibrations have substantial contribution
from the ring CCC in-plane and out of plane bending, respec-
tively. The C–H(Cl2) in-plane and out of plane bending vibrations
are significantly mixed with CC in-plane and out of plane modes,
respectively.
4.3.3. Amide group vibrations
The amide (–CONH–) group vibrations of the compounds
investigated are correlated with the unsubstituted N-phenyl-2,2-
dichloroacetamide (NPA) vibrations [1] and presented in Table 6.
In N-phenylacetamide structure there is competition between the
phenyl ring and the C O for the lone pair of electrons of the nitro-
gen. Amide-I band, the C O stretching mode is the strongest band
in the infrared spectrum and appears with diminished intensity in
the Raman spectrum. Hence the very strong IR bands observed at
1677 and 1669 cm−1 is assigned to the amide-I band of 2MPA and
4MPA molecules, respectively. The Raman counterpart are obtained
as strong band at 1674 and 1669 cm−1, respectively. The comparison
of the wavenumber of C O stretching in 2MPA and 4MPA with that
of NPA molecule reveals that the substitution of methyl group in
the phenyl ring does not makes the molecule effectively compete
with the carbonyl oxygen for the electrons of the nitrogen, thus
increasing the force constants of the C O bond. It is evident from
the infrared and Raman vibrational frequencies of 2MPA and 4MPA,
that the C O stretching frequencies of the compounds under inves-
tigation does not show significant variation from that of the parent
compound N-phenyl-2,2-dichloroaetamide.
Secondary amides shows only one N–H stretching band in the
infrared spectrum between 3370 and 3170 cm−1. A weaker band
may appear at about 3100 cm−1 in secondary amides due to Fermi
resonance of 1550 cm−1. The exact location of the N–H stretch-
ing mode depends upon the other groups adjacent to the –CONH–
skeleton [1]. Thus the very strong band observed at 3250 cm−1
in IR and 3247 cm−1 in Raman is attributed to the N–H stretch-
ing of 2MPA molecule. The 4MPA shows the characteristic very
strong N–H stretching band at 3240 in the IR and at 3236 cm−1 in
Raman spectrum. In comparison with NPA, the N–H stretching fre-
quencies of 2MPA and 4MPA compounds are invariably lowered by
20–30 cm−1. In N-phenylacetamide, the C O and N–H bonds may
be either cis or trans to each other. But the dipole moment measure-
ments, X-ray and neutron diffraction studies demonstrated that the
trans conformer is the predominant and most stable[11–15,65]. The
influence of the ring substituent on N–H stretching frequency of
N-phenylacetamide and its derivatives may be the resultant steric
effect, direct field effects, hydrogen bonding and bond polarisa-
tion effects. It has been shown that the mesomeric and inductive
effects of para substituents have little influence on the N–H stretch-
ing frequencies, and it is reasonable to assume that polarisation
interactions of ortho substituents likewise have little effect on N–H
stretching frequency [67].
The steric effect of ortho substituent must be considered in con-
junction with the conformations. The increase in N–H stretching
frequency may be expected in introduction of an o-methyl group
into the phenyl ring of N-phenylacetamide. It is not due to the direct
field effect but because of the steric interactions. If the most intense
N–H stretching band is assigned to the trans conformer-II, then N–H
stretching frequency is increased by about 15 cm−1 on introduction
of an ortho-methyl substituent into N-phenylacetamide. The alkyl

V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
615
Table 6
Correlation of amide (–CONH–) group vibrations of the compounds investigated.
Compounds name
␯
C
␤
␯
␤
C
␥
N–H
␥
C
␯
N–H
O
N–H
C–N
O
O
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
FTIR
FTR
NPAa
2MPA
4MPA
1672
1677
1669
1680
1674
1669
1555
1588
1551
1568
1590
1546
1344
1341
1348
1355
1350
1340
811
807
810
810
800
809
712
717
745
715
725
744
558
667
636
568
675
638
3270
3250
3240
3275
3247
3236
a
Values are taken from Ref. [1].
substituents should not exert sizable direct field effects and the
observed frequency increases are therefore an appropriate measure
of the steric interactions.
4MPA, respectively. The asymmetric stretching of 2MPA, ␯a(CH3)
is assigned at 3006 and 3010 cm−1, while in the case of 4MPA the
mode is observed at 2936 cm−1 under Aꢀ species. The strong depo-
larised frequencies seen at 2992, 3002 and 3003 cm−1 in the spectra
of 2MPA and 4MPA are attributed to the ␯a(CH3) under A” species.
The asymmetrical methyl deformation mode, ␦a(CH3) of 2MPA and
4MPA are observed at 1487 and 1475 cm−1 under Aꢀꢀ species cor-
responding to 2MPA and 4MPA, respectively. The very strong to
medium bands at 1328 and 1307 cm−1 in the infrared spectra and at
1330 and 1308 cm−1 in Raman spectra of 2MPA and 4MPA, respec-
tively are attributed to the methyl symmetric deformational modes
␦s(CH3) in the Aꢀ species [36,44,68]. The other bending vibrational
frequencies of methyl group are clearly indicated in Tables 4 and 5.
The normal co-ordinate analysis shows that the methyl wagging
mode is effectively mixed with the out of plane C–H mode.
In the present investigation, it is observed that there is no
increase in the N–H stretching frequencies of 2MPA and 4MPA
than that of N-phenyl-2,2-dichloroacetamide. This clearly confirms
that the steric effect due to o-methyl group is not significantly
operating on the N–H stretching and it also reveals that the
compound 2MPA exist in the favoured trans configuration-I. The
calculated energies of the conformers (EI = −1398.74663396 a.u.)
and (EII = −1398.73065843 a.u.) also favourable.
4.3.5. CCl2 group vibrations
The C–Cl absorption is observed in the broad region between
850 and 550 cm−1. When several chlorine atoms are attached to
one carbon atom, the band is usually more intense and at high fre-
quency end of the assigned limits. In view of this, the strong and
medium bands in IR at 769 and 792 cm−1 having the Raman coun-
terpart at 777 and 793 cm−1 are assigned to the asymmetric CCl2
stretching wavenumber of 2MPA and 4MPA molecules, respectively.
The symmetric CCl2 stretching is observed at 703 and 668 cm−1 in
2MPA and 4MPA, respectively. The CCl2 asymmetric and symmet-
ric stretching frequencies of 2MPA and 4MPA does not show any
appreciable variation from that of the corresponding frequencies
in NPA. The in-plane CCl2 deformation vibrations and the out of
plane CCl2 twisting and wagging modes are obtained in the low
frequency region of the Raman spectra as medium to strong bands.
These assignments are in good agreement with the literature values
[1,69] and well supported by normal coordinate analysis. The CCl2
wagging mode significantly overlaps with CCl2 twisting mode and
vice versa and also the in-plane C–H bending vibrations contributed
to CCl2 deformation and rocking modes.
The frequencies observed at 1588 and 1551 cm−1 in IR are
ascribed to the amide-II band, N–H in-plane bending mode of 2MPA
and 4MPA, respectively. The corresponding Raman counterparts
are obtained at 1590 and 1546 cm−1. The C–N stretching mode,
the amide-III band, of 2MPA is assigned at 1341 and 1350 cm−1 in
IR and Raman spectra, respectively. The fundamental mode seen
at 1348 cm−1 in IR and 1340 cm−1 in Raman are assigned to the
C–N stretching of 4MPA. The amide-III band of NPA is observed
at 1344 cm−1 in the infrared while in Raman it is observed at
1355 cm−1. The spectral data indicates that no rise in C–N stretching
frequencies of 2MPA and 4MPA and there is no hyper conjugative
influence of the methyl group towards the C–N bond.
The amide-IV, C O in-plane bending of 2MPA is found at 807 and
800 cm−1 in the IR and Raman, respectively. For 4MPA compound
this mode is seen at 810 and 809 cm−1. There is no significant shift
in the C O in-plane bending, frequencies of 2MPA and 4MPA com-
poundsthanthatofNPA. Theamide-V, theN–Houtofplanebending
is observed as strong and medium bands at 717 and 725 cm−1 in
5. Conclusion
The molecular structural parameters, thermodynamic proper-
ties and vibrational frequencies of the fundamental modes of the
optimisedgeometryof2MPAand4MPAhavebeendeterminedfrom
HF and DFT-B3LYP methods. The FTIR and FT-Raman vibrational
frequencies of the compounds under investigations revealed close
similarities in the magnitudes of the frequencies in spite of the fact
that the substituents in the phenyl ring are at different positions.
The comparison of the fundamental vibrations, the following obser-
vations are made: The magnitude of C O frequency variation is
also not significantly influenced by the position of methyl groups
present. In the present investigation, there is no increase in the
N–H stretching frequency of 2MPA and 4MPA than that of N-phenyl-
2,2-dichloroacetamide, clearly confirms that the steric effect due to
o-methyl group is not significantly operating on the N–H stretching
and it also reveals that the compounds under investigations takes
the favoured trans configuration-I, predominantly. The comparison
ofotheramidegroupfrequenciesdidnotshowanyappreciablevari-
2MPA and this mode is seen at 745 and 744 cm−1 in 4MPA. The C
O
out of plane bending of 2MPA is seen at 667 and 675 cm−1 in IR and
Raman, respectively. In 4MPA this amide-VI band is observed at 636
and 638 cm−1. Both the amide-V and amide-VI out of plane bend-
ing modes of 2MPA and 4MPA is significantly raised than that of
NPA. The PED calculations determine that the amide-IV and amide-
VI bands possessing the character of N–H vibrations by mixing. The
amide-V bands of 2MPA and 4MPA are significantly overlapped C
out of plane bending vibrations.
O
4.3.4. Methyl group (–CH3) vibrations
Considering the assignments of –CH3 group frequencies, the
asymmetric stretching and asymmetric deformation modes of the
–CH3 group would be expected to be depolarised for Aꢀꢀ symme-
try species. The symmetric, ␯s(CH3) frequencies are established
at 2925, 2923 and 2919, 2920 cm−1 in the spectra of 2MPA and

616
V. Arjunan et al. / Spectrochimica Acta Part A 74 (2009) 607–616
ationintherespectivewavenumbersexcepttheamideIVband, C
O
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mode of the compounds. The basis set 6-311++G(d,p), is reliable for
the determination of the electronic structure by quantum chemical
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