Substituent effect investigation of 3-(2, 4-dichlorophenyl)-1-(4′-X- phenyl)-2-propen-1-one. Part 1. Correlation analysis of 13C NMR chemical shifts

Article abstract of DOI:10.1002/poc.1718

A series of substituted chlorinated chalcones namely, 3-(2,4- dichlorophenyl)-1-(4′-X-phenyl)-2-propen-1-one, have been synthesized, X being H, NH₂, OMe, Me, F, Cl, CO₂Et, CN, and NO ₂. Dual substituent parameter (DSP) mod

Full text of DOI:10.1002/poc.1718

Research Article
Received: 11 November 2009,
Revised: 8 March 2010,
Accepted: 15 March 2010,
Published online in Wiley Online Library: 8 July 2010
(wileyonlinelibrary.com) DOI 10.1002/poc.1718
Substituent effect investigation of 3-(2,
4-dichlorophenyl)-1-(40-X-phenyl)-2-propen-
1-one. Part 1. Correlation analysis of
13C NMR chemical shiftsy
a
b
b
c
*
´
´
´
A. Perjessy , H. K. Al-Amood , G. F. Fadhil and N. Pronayova
A series of substituted chlorinated chalcones namely, 3-(2,4-dichlorophenyl)-1-(4(-X-phenyl)-2-propen-1-one, have
been synthesized, X being H, NH2, OMe, Me, F, Cl, CO2Et, CN, and NO2. Dual substituent parameter (DSP) models of 13
C
NMR chemical shift (CS) have revealed that p-polarization concept could be utilized to explain the reverse field effect
at CO, the enhanced substituent field effect at CO, C-2, and C-5, and the decreased sensitivity of substituent field effect
at C-6. Chlorine atoms dipole direction at the benzylidene ring either enhances or reduces substituent effect
depending on how they couple with the substituent dipole at the probe site. The correlation of 13C NMR CS of
C-2, C-5, and C-6 with sPR and sRR indicates that chlorine atoms in the benzylidine ring deplete the ring from charges.
Both MSP of Hammett and DSP of Taft 13C NMR CS models give similar trends of substituent effects at C-2, C-5, and C-6.
However, the former fail to give a significant correlation for CO and C-6 13C NMR CS. MSP of sq and DSP of Taft and
Reynolds models significantly correlated 13C NMR CS of Cb. MSP of sq fails to correlate C-1( 13C NMR CS. Investigation
of 13C NMR CS of non-chlorinated chalcones series: 3-phenyl-1-(4(-X-phenyl)-2-propen-1-one has revealed similar
trends of substituent effects as in the chlorinated chalcones series for C-1(, CO, Ca, and Cb. In contrast, the substituent
effect of the non-chlorinated chalcone series at C-2, C-5, and C-6 did not correlate with any substituent constant.
Copyright ß 2010 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this paper.
Keywords: 13C NMR chemical shifts; chalcones; correlation analysis; substituent effect
where r, rR, and rF are the weighting factors of electronic,
INTRODUCTION
resonance, and field substituent effects, respectively, with c being
the intercept in each model. These models have demonstrated
the versatility of both the MSP and DSP in interpreting the mode
of transmission of substituent electronic, resonance, and field
effects.
Sotomatsu et al.[16] found a significant correlation between
Hammett’s substituent constant and the sum of Mulliken charges
of the carboxyl group of various para and meta substituted
benzoic acids calculated by semi-empirical AM1 method.
Saleh[17] defined sq constant from the sum of calculated Mulliken
Chalcones have shown immense chemical and biological
applications such as antimalarial,[1] antiplasmodial,[2] anti-HIV,[3–5]
anti-cancer,[6,7] and anti-bacterial.[8] Also, chalcones have been
objects of a number of theoretical[9,10] and experimental[11,12]
structural investigations. Earlier studies on the transmission of
substituent effects on substituted chalcones namely 3-phenyl-
1-(40-X-phenyl)-2-propen-1-ones, 3-(4-X-phenyl)-1-(phenyl)-2-propen-
1-ones,[13,14] and trans-1-phenyl-3-(5-aryl-2-furyl) propenones and
trans-1-phenyl-3-(5-aryl-2-thienyl) propenones[15] have revealed the
electronic nature of substituent effect. These conclusions were
based on the correlation of the 13C NMR CS or carbonyl stretching
frequencies as represented by Px for compound with X being the
substituent and s being the Hammett substituent constant.
Equation (1) represents the mono substituent parameter model
(MSP). There has been some dispute about using the MSP over the
dual substituent parameter model (DSP). The former model is
simple and gives one weighting factor to interpret the
transmission of substituent effect. However, the failure of the
MSP in certain cases has encouraged researchers to use the DSP
(Eqn 2), which uses sR and sF substituent resonance and field
constants, respectively. Nevertheless, in certain cases the MSP
provides better modeling results than the DSP.
*
Correspondence to: G. F. Fadhil, Department of Chemistry, College of Science,
University of Basrah, Basrah, Iraq.
E-mail: ghazwan_fadhil@yahoo.co.uk
´
a
b
A. Perjessy
Institute of Chemistry, Comenius University, SK-84215 Bratislava, Slovak
Republic
H. K. Al-Amood, G. F. Fadhil
Department of Chemistry, College of Science, University of Basrah, Basrah,
Iraq
´
´
c
N. Pronayova
Department of NMR MS, Institute of Analytical Chemistry, Slovak University of
Technology, Bratislava, Slovak Republic
´
In Memoriam the late professor Alexander Perjessy
Px ¼ r s þ c
Px ¼ rR sR þ rFsF þ c
(1)
(2)
y
J. Phys. Org. Chem. 2011, 24 140–146
Copyright ß 2010 John Wiley & Sons, Ltd.

CORRELATION ANALYSIS OF 13C NMR CHEMICAL SHIFTS
charges[16] of the carboxyl group atoms in para or meta
substituted benzoic acid.
General procedure for the synthesis of 3-(2,
4-dichlorophenyl)-1-(4(-X-phenyl)-2-propen-1-one
In recent substituent effect studies on 13C NMR CSs and
carbonyl stretching frequencies in E-2-(X-benzylidene)-
1-indanones, E-2-(X-benzylidene)-1-tetralone, and E-2-(X-benzy-
lidene)-1-benzosuberones,[18,19] each structure contains the
a,b-unsaturated ketone functionality. This makes the molecular
framework similar to chalcones. It has been concluded[18,19] that
the carbon atom a of the side chain, which is next to carbon para
of the substituted benzene ring, is less sensitive to substituent
effect than the b-carbon. However, there was little elaboration on
the origins of the field effects in terms of p-polarization.
The p-polarization concept was proposed originally by Hamer
et al.[20,21] and later was used extensively by Bromilow et al.[22]
and Brownlee et al.[23,24] to rationalize substituent field effect at
the side chain of para and/or meta substituted benzenes. It was
also successfully applied to interpret the transmission of
substituent effects within 5-substituted indole -2, 3-diones.[25]
The p-polarization concept was recently used successfully to
interpret the Yukawa–Tsuno model of 13C NMR CS of b-carbon of
the vinyl group in para substituted styrenes with varying
electronic demands at b-carbon.[26] Hence, applying MSP and
DSP models to 13C NMR CS and then interpreting the obtained r
of MSP and rR and rF of DSP – in terms of the electronic effects or
resonance and field effects of substituent with the aid of the
p-polarization concept – would be a worthwhile analysis to
rationalize the mode of transmission of substituent effects
through aromatic molecules. Previous structural investigations
have not covered chalcones with a chlorinated benzylidine
ring.[13–15] These chlorine atoms may alter the substituent effect
felt at the benzylidine ring. Hence, the aim of this work is to
investigate the mode of transmission of substituent effect
and test the quality of MSP and DSP models in modeling 13C NMR
CS in 3-(2,4-dichlorophenyl)-1-(40-X-phenyl)-2-propen-1-ones
(Structure 1).
Condensation of 2, 4-dichlorobenzaldehyde with 4-X-aceto-
phenone was carried out to prepare the suitable 3-(2,
4-dichlorophenyl)-1-(40-X-phenyl)-2-propen-1-one
(Chalcone).
However, two different procedures were employed according
to the type of substituent, X, in the acetophenone. Chalcones
with substituent X, namely H, NH2, OMe and Me, were prepared
according to the Claisen–Schmidt method[27–29] with a slight
modification to the concentration of the base in which 20% of
NaOH was used for the preparation of chalcones with
substituents H and OMe. Chalcones with substituent X, namely
F, CN and NO2, were prepared by passing HCl gas on ethanolic
solution of the 2, 4-dichlorobenzaldehyde and para substituted
acetophenone in (1:2) mole ratio, respectively.[30] However,
chalcone with substituent CO2Et was prepared in situ by
hydrolysis and then ethanolysis of the 3-(2, 4-dichloro-
phenyl)-1-(40-cyano-phenyl)-2-propen-1-one. Products were
recrystalized from ethanol. Table S1 gives the yields percentages,
physical properties, uncorrected melting points and retention
factors for the prepared compounds. CHN analysis is presented in
Table S2.
Proton NMR assignments
Table S3 shows proton NMR spectra. Scheme 1 shows proton
designation and carbon atom numbering. Protons on ring B
showed an AMX pattern of splitting, while protons on ring A
showed an AA0BB0 pattern of splitting. The vinyl protons gave an
AB pattern of splitting.
13C NMR spectra assignments
Table 1 presentsthe measured 13C NMR CS. Thecalculated 13C NMR
CS are presented in parenthesis. Additivity rules of the software
ChemBioDraw Ultra 11[31] were used to calculate the expected
13C NMR chemical shifts. 13C NMR CS of the carbonyl, alpha, and
beta were assigned according to Reference [14]. Calculated
13C NMR chemical shifts of ring B, CO, Ca, and Cb according to
Reference [31] were insensitive to the variation of the substituents.
They are given for the unsubstituted compound only; substituted
compounds showed the same values of calculated 13C NMR CS.
Difference in peak intensities of substituted and unsubstituted
carbons aided in peak assignments.
EXPERIMENTAL SECTION
COMPUTATIONS
General procedures
Statistical calculations
Melting points were uncorrected and measured by using
Gallenkamp melting point apparatus. Proton NMR spectra were
recorded on a Varian VXR 300 NMR spectrometer (299.943 MHz)
.
in CDCl3 at 25 8C with a concentration of 0.02 mlꢀ1 13C NMR
A standard statistical package was used to calculate r, R,
regression coefficient rs, and standard deviation (SD) of model fit.
f-statistics[32] was used to judge the quality of the constructed
spectra were recorded on the same spectrometer at (75.429 MHz)
in CDCl3 solvent at 25 8C and referenced with respect to TMS in
ppm. The Proton decoupling technique was used to aid the 13C
assignment. A concentrated solution in CDCl3 was used. For
compounds with X as NH2, a small amount of CD3OD was added
to increase its solubility in CDCl3. The follow-up of reactions and
sample purity were checked by TLC using Merck silica gel 60 F254
aluminum sheets and were developed with the solvent mixture
indicated in Table S1.
Scheme 1.
J. Phys. Org. Chem. 2011, 24 140–146
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View this article online at wileyonlinelibrary.com

´
A. PERJESSY ET AL.
13
Table 1. C NMR CS in ppm of 3-(2, 4-dichlorophenyl)-1-(40-X-phenyl)-2-propen-1-one
X
C-a
C-b
C-1
C-2
C-3
C-4
C-5
C-6
H
125.01
(124.3)
124.74
125.48
125.04
124.54
124.39
124.76
124.06
139.31
(145.1)
138.05
138.44
138.88
139.55
139.79
140.45
141.13
131.85
(131.1)
131.85
132.07
131.96
131.70
131.62
131.56
131.14
136.07
(136.0)
135.69
135.92
136.00
136.10
136.03
136.22
136.31
130.14
(128.9)
129.83
130.05
130.09
130.17
130.18
130.21
130.26
136.47
(125.2)
136.02
136.18
136.31
136.59
136.14
136.81
137.18
127.56
(126.8)
127.34
127.48
127.51
127.58
127.59
127.63
127.67
128.50
(130.3)
128.33
128.44
128.46
128.49
128.49
128.53
128.53
NH2
OCH3
CH3
F
Cl
CO2Et
NO2
X
CO
C-10
C-20,60
C-30,50
C-40
Others
H
190.07
(189.7)
188.20
137.77
(137.9)
128.83
(127.9)
130.63
(130.2)
135.15
(134.9)
134.09
(133.5)
136.67
(136.0)
141.04
(142.2)
128.71
(128.5)
131.05
(132.0)
130.92
(130.9)
128.75
(128.8)
131.16
(131.5)
130.00
(130.3)
128.45
(129.8)
128.60
(129.2)
115.35
(114.7)
113.90
(114.8)
129.40
(129.5)
115.87
(116.0)
129.04
(129.3)
129.86
(130.4)
133.08
(134.5)
149.28
(154.2)
163.60
(166.4)
144.00
(144.2)
165.74
(168.7)
139.55
(140.1)
134.15
(135.9)
NH2
OCH3
CH3
F
188.20
189.55
188.43
188.76
189.78
55.50 (OCH3) (55.80)
21.71(CH3) (21.3)
Cl
CO2Et
13.30 (14.1)(CH3)
61.51(60.9) (OCH2)
165.74 (165.9)(CO)
NO2
188.63
142.46
(144.0)
129.48
(130.8)
123.88
(124.4)
150.14
(153.7)
1J(13C,19F) ¼ 255.18 Hz, orthoJ(13C,19F) ¼ 22.1 Hz, metaJ (13C,19F) ¼ 9.28 Hz, and paraJ (13C,19F) ¼ 2.87 Hz. Bracketed values are calculated
CS in ppm.
13
model, and were calculated by dividing the SD of the model over
the root mean square error of data. The lower the f-statistics the
better is the model. Excluded substituents in modeling due to
lack of substituent constant are indicated at the bottom of
Tables 2 and 3.
correlated C NMR CS of C-10 and Cb better than Taft’s DSP
model, which also uses sR8 as a substituent constant. In general,
DSP models give better modeling quality than MSP models. rR
values for a given carbon responded in a similar fashion in both
Reynolds’ and Taft’s DSP models as long as the latter uses of sR8
as the best substituent resonance parameter, and both models
had a similar quality of significance as given by R values. This
result can be ascribed to the nature of Reynolds’ sR8. rR in
Reynolds’ model for 13C-10 NMR CS is 4.77 times larger than rF for
the same atom. This implies more substituent resonance
contribution in C-10 than field effect. This behavior of C-10 was
found previously in para-disubstituted benzenes.[33] Taft’s DSP
model is superior in quality to Reynolds’ DSP model in modeling
13C NMR CS of C-CO. The 13C NMR CS of C-CO behaves in a reverse
manner to the substituent effect. This means the electro-
n-withdrawing substituent causes an up-field shift to NMR
chemical shifts of 13C-CO. Despite that, a positive value of rR was
observed in modeling 13C-CO NMR CS by Reynolds’ and Taft’s DSP
models with sþR being the best substituent resonance constant in
the latter model. It has been observed[34] that 13C-CO NMR CS of
acetophenone responds normally to substituent resonance effect
with rR being positive. The 13C-CO NMR CS in the current study
behaves in a similar fashion to that of acetophenone. However,
for para substituted benzoate the 13C-CO NMR CS gives a
RESULTS AND DISCUSSION
Table 1 shows the variations of 13C NMR CS values when changing
the substituent in structure 1. Tables 2 and 3 provide the results of
modeling 13C NMR CS via the MSP and DSP models, respectively.
The MSP of sq and DSP models were equally significant in
modeling 13Cb NMR CS as indicated by r, R, and f-statistics. None
of the MSP models provided significant correlation with 13C-CO
NMR CS. Hammett type spþ was better than sq in correlating 13C
NMR CS of C-10, C-2, C-5, and C-6 as concluded from the higher r
and lower f-statistics values for Hammett’s model. Similarly, Taft’s
DSP model selected sþR as the best substituent constant to
correlate 13C NMR CS of C-2, C-5, and C-6. The selection of sþp and
sþR in MSP and DSP models, respectively, indicates that C-2, C-5,
and C-6 may suffer a deficiency of charge. Hence, the failure of
Reynolds’ DSP model in correlating 13C NMR CS of C-2, C-5,
andC-6 can be understood since his model uses sR8 as a
substituent resonance constant. However, Reynolds’ DSP model
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CORRELATION ANALYSIS OF 13C NMR CHEMICAL SHIFTS
Table 2. Results of 13C NMR CS MSP modeling of chlorinated chalcones
Hammett’s Modela
Substituent
constant
C-atom
c
r
r
f-statistics
C-10
CO
136.59 ꢁ 0.45
189.01 ꢁ 0.25
139.46 ꢁ 0.14
136.07 ꢁ 0.02
127.56 ꢁ 0.01
128.48 ꢁ 0.01
6.86 ꢁ 0.72
0.53 ꢁ 0.39
2.12 ꢁ 0.33
0.28 ꢁ 0.03
0.15 ꢁ 0.01
0.09 ꢁ 0.01
0.968
0.478
0.930
0.972
0.972
0.948
0.26
0.54
0.41
0.27
0.27
0.35
spþ
spþ
sBpA
spþ
spþ
spþ
C-b
C-2
C-5
C-6
sq Modelb
C-atom
c
r
r
f-statistics
C-10
CO
C-b
C-2
C-5
C-6
250.99 ꢁ 22.7
190.37 ꢁ 8.9
167.19 ꢁ 1.7
140.94 ꢁ 0.8
130.19 ꢁ 0.5
129.96 ꢁ 0.4
267.0 ꢁ 52.2
3.50 ꢁ 20.4
64.20 ꢁ 3.9
11.30 ꢁ 1.8
6.13 ꢁ 1.2
0.916
0.077
0.991
0.942
0.914
0.837
0.40
0.56
0.15
0.36
0.45
0.59
3.46 ꢁ 1.0
c is the intercept.
a CN was excluded.
b CO2Et and CN were excluded.
Table 3. Results of 13C NMR CS DSP modeling of chlorinated chalcones
Taft’s Model
Substituent
constant
C-atom
c
rI
rR
R
f-statistics
C-10
CO
sR8
sRþ
sR8
sRþ
sRþ
sRþ
137.15 ꢁ 0.46
189.88 ꢁ 0.14
139.26 ꢁ 0.07
136.06 ꢁ 0.03
127.55 ꢁ 0.01
128.48 ꢁ 0.02
4.74 ꢁ 1.04
ꢀ2.00 ꢁ 0.29
2.35 ꢁ 0.18
0.29 ꢁ 0.07
0.17 ꢁ 0.03
0.07 ꢁ 0.03
11.90 ꢁ 0.79
0.95 ꢁ 0.13
2.96 ꢁ 0.17
0.25 ꢁ 0.03
0.14 ꢁ 0.01
0.09 ꢁ 0.01
0.991
0.976
0.995
0.981
0.991
0.965
0.15
0.13
0.12
0.24
0.17
0.30
C-b
C-2
C-5
C-6
Reynolds’ Modela
C-atom
c
rF
rR
R
f-statistics
C-10
CO
C-b
C-2
C-5
C-6
137.63 ꢁ 0.29
3.88 ꢁ 0.64
ꢀ2.23 ꢁ 0.44
2.31 ꢁ 0.18
0.29 ꢁ 0.13
0.18 ꢁ 0.09
0.08 ꢁ 0.07
18.50 ꢁ 0.70
2.59 ꢁ 0.48
3.04 ꢁ 0.19
0.63 ꢁ 0.14
0.32 ꢁ 0.09
0.21 ꢁ 0.08
0.998
0.956
0.996
0.944
0.919
0.856
0.07
0.18
0.10
0.40
0.48
0.60
189.97 ꢁ 0.20
139.25 ꢁ 0.08
136.05 ꢁ 0.06
127.54 ꢁ 0.04
128.48 ꢁ 0.03
c is the intercept.
a CN was excluded.
J. Phys. Org. Chem. 2011, 24 140–146
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´
A. PERJESSY ET AL.
gives a rI value almost twice rR for 13C-CO NMR CS. Thus, the
predominance in the 13C-CO NMR CS value is for the substituent
field effect, explaining the reverse behavior of the 13C-CO NMR
CS. The reverse substituent field effect (i.e. negative rI) can be
rationalized as a result of the p-polarization of the molecular
framework. Structure 2 depicts the p-polarization in the studied
molecule. A partial negative charge appears at C-CO, reflecting
the reverse nature of the substituent field effect felt at that
carbon. However, the positive sign of rR for 13C-CO NMR CS
indicates a normal substituent effect as explained pre-
viously.[35,36]
MSP and DSP models failed to correlate 13Ca NMR CS. This
failure was observed with other chalcones;[14] it might be related
to the insensitivity of 13Ca NMR CS to the variation of substituents.
In contrast, 13Cb NMR CS showed a significant correlation in sq
MSP model. DSP models for 13Cb NMR CS generated more
significant results than MSP models. Reynolds’ DSP model was
better than Taft’s, but both indicated more substituent resonance
effect than substituent field effect at Cb. However, the rR/rI and
rR/rF of C-10 are much larger than at Cb. Structure C of Scheme 2
shows that C-10 is in through resonance, while Cb is not. The
correlation of 13Cb NMR CS with sR8 of Taft and sR8 of Reynolds
indicates that the substituent is not in direct resonance with Cb.
sþp of Hammett’s MSP and sþR of Taft’s DSP significantly correlate
13C NMR CS of C-2, C-5, and C-6, while sq and Reynolds’ DSþP
model fail to do so. The selection of sþp in the MSP model and sR
in the DSP model as the best substituent parameters may indicate
an electron deficiency at C-2, C-5, and C-6. This could be
attributed to the chlorine atoms in the benzylidene ring. The rR
C-2/rR C-6 being 2.77 and rC-2/rC-6 being 3.11 are close results from
using different models and confirm the increased substituent
resonance effect sensitivity at C-2 over that of C-6, which can be
ascribed to the chlorine atom at C-2. The chlorine atom depletes
the C-2 from electrons and, hence, the 13C NMR CS of C-2
significantly correlates with sþp and sRþ with r and rR, respectively,
and is higher than that of C-6 which lacks a chlorine atom. The rR
C-5/rR C-6 and rC-5/rC-6 were 1.56 and 1.67, respectively. This trend
of rR C-5/rR C-6 and rC-5/rC-6 is similar to that observed in C-2
but to a lesser extent because of C-5 being indirectly connected
to the chlorine atom as in C-2. The substituent field effect felt
at C-2, C-5, and C-6 was normal, i.e. positive values of rj or rF
with a rate of fall C-2 > C-5 > C-6. This trend of fall coincides
with the rate of fall of rR for the same atoms. Enhanced rF and
rR values in Reynolds’ DSP model were observed[26] for 13Cb NMR
CS of para substituted styrene when the Cb atom becomes
bonded to a more electronegative atom or polarizable functional
group.
Scheme 2.
negative rR. This phenomenon is called the reverse substituent
resonance effect.
The p-polarization along the conjugated p-electron system
was found to be under the influence of the substituent at the para
substituted benzene ring A.[20–24] The p-polarization concept
assumes that each p-unit (a double or triple bond, carbonyl,
nitrile, or aromatic system) is thought to be polarized separately,
the polarization being induced by the substituent dipole in
another part of the molecule. This type of p-polarization is called
localized or direct p-polarization. The localized p-polarization
can be transmitted through either the molecular framework or
the solvent continuum. In localized p-polarizations, each p-unit in
the side chain polarizes separately.
It has been claimed[35] that in cases of acetophenones
resonance, structure C of Scheme 2 is more important than
the resonance structure B of Scheme 2. However, in the case of
ethyl benzoates, the resonance structure B of Scheme 2 is more
important than resonance structure C.
Structure 2 shows the resultant dipole due to chlorine atoms at
carbon atoms 2 and 4. The resultant dipole stabilizes the
p-polarization at C-2 because of its proximity of partial positive
charge and of the resultant chlorine dipole to the partial negative
charge generated by the substituent field effect at C-2. However,
when a positive charge due to the substituent field effect exists
such as at C-5, a lower rI value is observed due to destabilization
by similar charge repulsion. A lower rI value than that at C-2 is
also observed when the resultant dipole is felt at C-6 in the
opposite direction to the substituent field dipole.
Structure 2.
The rI/rR for C-2 and C-5 was 1.16 and 1.21, respectively, while
the rI/rR for C-6 was 0.78. These rates of fall indicate that rI at C-6
is more sensitive to the destabilizing effect of the resultant dipole
of the chlorines atoms C-2 and C-4 than rR, which maintained a
higher value than rI.
Thus, in this study we may argue that resonance structure C is
more important than structure B because rR is positive.
Nonetheless, both DSP models give a reverse substituent field
effect i.e. negative values of rI for the 13C-CO NMR CS. Taft’s model
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Copyright ß 2010 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 140–146

CORRELATION ANALYSIS OF 13C NMR CHEMICAL SHIFTS
Table 4. Results of 13C NMR CS MSP modeling of non-chlorinated chalconesa
Hammett’s Model
Substituent
constant
C-atom
c
r
r
f-statistics
C-10
CO
136.49 ꢁ 0.39
188.88 ꢁ 0.27
144.75 ꢁ 0.18
128.78 ꢁ 0.05
129.34 ꢁ 0.29
128.78 ꢁ 0.05
7.73 ꢁ 0.80
0.26 ꢁ 0.56
2.45 ꢁ 0.43
0.17 ꢁ 0.10
ꢀ0.50 ꢁ 0.59
0.17 ꢁ 0.10
0.974
0.207
0.939
0.605
0.352
0.605
0.26
0.54
0.38
0.84
0.86
0.86
spþ
spþ
sBpA
spþ
spþ
spþ
C-b
C-2
C-5
C-6
sq Model
C-atom
c
r
r
f-statistics
C-10
CO
C-b
C-2
C-5
C-6
253.48 ꢁ 27.21
188.22 ꢁ 9.41
179.72 ꢁ 3.55
132.69 ꢁ 1.18
127.51 ꢁ 10.47
132.69 ꢁ 1.18
270.0 ꢁ 63.33
ꢀ1.60 ꢁ 21.90
80.73 ꢁ 8.25
9.06 ꢁ 2.75
0.886
0.032
0.975
0.828
0.077
0.828
0.53
0.55
0.23
0.59
0.91
0.59
ꢀ4.15 ꢁ 24.38
9.06 ꢁ 2.75
c is the intercept.
a Substituent set: H, CH3, OCH3, F, Cl, CN and NO2.
Table 5. Results of 13C NMR CS DSP modeling of non-chlorinated chalconesa
Taft’s Model
C-atom
Substituent constant
c
rI
rR
R
f-statistics
C-10
CO
137.55 ꢁ 0.43
189.77 ꢁ 0.19
144.52 ꢁ 0.08
128.66 ꢁ 0.06
128.46 ꢁ 0.38
128.66 ꢁ 0.06
4.85 ꢁ 0.92
ꢀ1.85 ꢁ 0.34
2.66 ꢁ 0.17
0.46 ꢁ 0.13
1.43 ꢁ 0.79
0.46 ꢁ 0.13
12.98 ꢁ 0.88
1.15 ꢁ 0.22
3.19 ꢁ 0.20
0.05 ꢁ 0.09
ꢀ1.27 ꢁ 0.51
0.05 ꢁ 0.09
0.993
0.962
0.996
0.877
0.818
0.877
0.15
0.17
0.09
0.57
0.59
0.57
sBRA
sRþ
sR8
sRþ
sRþ
sRþ
C-b
C-2
C-5
C-6
Reynolds’ Model
C-atom
c
rF
rR
R
f-statistics
C-10
CO
C-b
C-2
C-5
C-6
138.01 ꢁ 0.31
189.96 ꢁ 0.96
144.49 ꢁ 0.08
128.66 ꢁ 0.08
128.44 ꢁ 0.45
128.66 ꢁ 0.08
3.72 ꢁ 0.64
18.59 ꢁ 0.83
0.997
0.974
0.997
0.838
0.777
0.838
0.09
0.14
0.08
0.65
0.64
0.65
ꢀ2.15 ꢁ 0.30
2.72 ꢁ 0.16
0.45 ꢁ 0.16
1.54 ꢁ 0.94
0.45 ꢁ 0.16
2.68 ꢁ 0.39
3.36 ꢁ 0.21
0.09 ꢁ 0.21
ꢀ2.76 ꢁ 1.23
0.09 ꢁ 0.21
c is the intercept.
a Substituent set: H, CH3, OCH3, F, Cl, CN, NO2.
J. Phys. Org. Chem. 2011, 24 140–146
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´
A. PERJESSY ET AL.
In order to investigate the role of chlorine atoms in the side
chain on the transmission of substituent effect, we have
investigated the substituent effect on the previously measured[14]
13C NMR CS in 3-phenyl-1-(40-X-phenyl)-2-propen-1-one as
chalcone with non-chlorinated side chain here upon called
non-chlorinated chalcone series. Tables 4 and 5 give the MSP and
DSP modeling results, respectively. The substituent effect trends
for C-10, CO, Cb, and Ca in the non-chlorinated chalcone series are
similar to the chlorinated chalcone series. Nevertheless, carbon
atoms of the benzylidine ring B in the non-chlorinated chalcone
series failed to correlate with any MSP or DSP model. This finding
could be attributed to the generated dipole by the chlorine
atoms bonded to carbon atom number 2 and 4 in the chlorinated
series. This dipole makes the C-2 and C-4 more sensitive to
respond to the substituent at para substituted benzene ring A.
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Copyright ß 2010 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2011, 24 140–146