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Substituent effects on the proton spin-spin coupling of benzenes with side-chain interacting groups
395 Journal of Molecular Structure, 16 (1973) 39.5402
@ EISeVier Scientific Publishing
Company,
Amsterdam
- Printed in The Netherlands
SUBSTITUENT EFFECTS ON THE PROTON SPIN-SPIN COUPLING BENZENES WITH SIDE-CHAIN INTERACTING GROUPS*
OF
D. G. DE KOWALEWSKl
Departanzento de Fisica, Fact&ad de Ciencias Exactas y Natwales, Consejo National de hvestigaciones, Buenos Aires (Argentina)
R. BUITRAGO
AND
Ciudad Uniuersitaria and
R. YOMMI
Departamento de Fisica Universidad de! Litoral, Santa Fe (Argentina) (Received
5 December
1972)
ABSTRACT
Sixty MHz NMR proton spectra of 15 2,4_substituted benzaldehydes and , I2 methylbenzenes dissolved in different solvents have been accurately analyzed. Substituent effects on the coupling constants have been determined and have been found to be additive in those trisubstituted compounds where there are neither I internal hydrogen bonds or strong interacting groups present.
INTRODUCTION
It was recently established’ that addivity relationships exist for substituent effects on the proton-proton coupling constants of trisubstituted benzenes. Due to the short-range effect of the tr electrons on Jnn, it was also possible to verify additivity relations in benzenes with more than one substituent”2-4, but some experimental results on ortho-disubstituted benzenes2 show that the additivity rule fails in cases of strongly interacting ortho substituents (OH, NOz; N02, NO2 ; CI, NO,). The ABC spectra of 37 benzenes with side-chain interacting groups (CHO, CHs) were analyzed in a similar way to that described in a previous work’ and the coupling constants were determined. The rest&s obtained with the additivity relations were then compared with those obtained from experimental data. * This work was sponsored
in part by the Consejo National
de Investigaciones
(Argentina).
396 EXPERIMENTAL The experimental procedure and the method of analysis follows the outlines the previous paper’ with addition that a second and eventuahy a third r.f. field (supplied as field modulation by two auxiliary audio osciliators) were applied to decouple each one of the resonances of the side-chain groups present in the molecule. As an example Fig. lb shows the methyl irradiated spectra of the Zbromo, 6-methylani~ine in methanol solution _ For those spectra in which the observed line broadening was expected to be due to a second side-chain long-range coupling a third r.f. field was applied. This was the case for the 2-chloro, 4-dimethylaminobenzaldehyde (Fig. 2~) and for all of the methoxy~~dehydes (Fig. 3b). Eight solvents were used (methanol, p-dioxane, Ccl,. CS, , dichloromethane, acetone, acetonitrile and nitromethane) until spectral lines of a haffwidth of 0.3 Hz were obtained. Sometimes a good solvent with Iow-viscosity had to be abandoned because its resonance was near that of the group to be irradiated of
“1
L....~....r....l....I....r....l....~...., -
75
m
(6
90
55
603
5
a
I-...,....,
um
n
ltMHZ
Fig. 1. (a) Frequency sweep proton 60 MHz spectrum of Zbromo, &methyIaniline in methanol solution; (b) Ring protons spectrum of the same substance recorded with simultaneous irradiation at the mean frequency of the CI-& group.
397
CHO
b)
Fig. 2. (a) Frequency sweep proton 60 MHz spectra of 2-chloro, Cdimethylamine benzaldehyde in acetonitrile solution; (b) The same spectra obtained when a second r-f. field is set on the N(CH& resonance: (c) Spectra obtained when the N(CHs)z and CHO resonances are strongly irradiated.
398
cno
I
d H2
Fig. 3. (a) Frequency sweep 60 MHz spectra of 3,4-dimethoxybenzaldehyde in acetonitrile solution; (b) Double irradiation experiments performed on the same solution_ The left side of the spectra was performed with the r.f. centered at the (OCH& resonance. The right side of the spectra was recorded while irradiating simultaneously the CHO and (OCH& resonances.
(ca. 10 Hz). This is one of the reasons why five out of the 27 substances were analyzed in only one solvent. All compounds used in this work were of commercial origin. In some cases, lines were identified as arising from impurities by the Indor technique5. Samples were measured as solutions of maximum possible concentration (IO-20 % w/w) in different solvents, with about 10 percent hexamethyldisiloxane as internal reference. All samples were degassed and seaIed under vacuum.
RESULTS
The ABC spectra of the ring protons of the trisubstituted benzenes were analyzed by means of the computer program LAOCN36. The signs of the coupling constants between the ring protons have been determined to be positive by many workers using various methods 7p8. Therefore, all the ring coupling constants were assumed to be positive. Table 1 gives the coupling constants of substituted benzaldehydes obtained from the decoupled spectra of substituted benzaIdehydes in different solvents,
399 together with their calculated root mean square (RMS) error. It can be seen that the precision of the .J values is much better than that in a previous work on benzaldehydesg where only the non-decoupled spectra of the substance, in one solvent, were calculated. Table 2 gives the coupling constants of methyl benzenes in different solvents. With the exception of two out of 57 solutions the maximum difference in the J values obtained for the same substance in different solvents is L-O.06 HZ. Table 3 shows the Es,, values corresponding to I, CHO, N(CH,),, CH, and Cl calculated from the monosubstituted benzene data’ and from the best available benzene Ji valueslo. Substituting into eqns. (l)-(3) of ref. 1 the vaIues of E,& for the different substituents and the values of Ji corresponding to benzene, the values of the proton-proton coupling constants of the substituted benzaidehydes and methyl benzenes can be calculated. TABLE
1
PROTON-PROTON
COUPLING
CONSTANTS
(in Hz)
OF BENZALDEHYDES
IN DIFFERENT
SOLVENTS
x
Y
z
Solvent
J ,t
J 24
J 14
RMS
CHO
Cl
Cl
CHO CHO
OCHJ OH
OCH, OH
OH
CHO
OH
CHO
NO,
NO+
CI,C CHJCOCHB CH&N CH&N CH3COCH3 CH30H CHaOH CH3CN CH,COCH, CHJZN
CHO
Cl
NWW,
OH
CHO
Cl
OH
CHO
Br
NO2
CHO
Cl
NOz
CHO
OH
OH
OH
CHO
Cl
Cl
CHO
OCHs
OCHJ
CHO
OH OH
NO2
CHO
CHO
NO2
8.387 8.514 8.603 8.594 8.605 8.579 8.91 I 8.891 8.516 8.602 8.973 8.941 8.952 8.894 8.83 I 8.928 8.900 8.763 8.788 8.686 8.998 9.018 8.200 8.066 8.233 8.202 8.184 8.205 8.244 8.637 9.224
I.942 1.982 2.25 1 2.262 2.247 2.222 3.060 3.076 2.189 2.197 2.523 2.496 2.690 2.712 2.666 2.566 2.520 2.388 2.365 2.392 2.776 2.799 1.915 1.908 1.921 1.911 1.916 1.916 1.916 1.722 2.838
0.336 0.224 0.301 0.274 0.248 0.239 0.432 0.473 0.365 0.371 0.179 0.213 0.377 0.379 0.388 0.346 0.290 0.389 0.337 0.270 0.286 0.253 0.366 0.310 0.361 0.332 0.180 0.199 0.138 0.410 0.327
0.006 0.013 0.023 0.006 0.029 0.010 O.‘olS 0.013 0.027 0.018 0.029 0.024 0.009 0.020 0.014 0.010 0.019 0.012 0.015 0.020 0.015 0.005 0.035 0.029 0.011 0.007 0.013 0.006 0.003 0.009 0.016
O(CHKHt)tO CH3CN CHsCN 0(CH&H2)20 CH,COCH, CH3COCH3 O(CHzCW,O CH3COCH3 CH$ZN O(CHrCW,O CH3COCHB CH3CN CHsCOCH3 O(CJ&<=H2)20
CH3COCH3 CH&N CH3COCH3 CHJCN CH30H O~CHzCH&O O(CHzCHd20
TABLE
2
PROTON-PROTON
COUPLING
CONSTANTS
(ill Hz)
OF METHYL
BENZENES
IN DIFFERENT
SOLVENTS
X
Y
2
Soiuent
J12
J24
Jl.%
RMS
CH3
I
NH2
CHBOH CHsCN
CHs
I
NO2
CH3
Cl
NO2
%(;H,CH,),O Cf 2CH2 CHaCN Cl& tCH,)tCO CHJZN c&c CIICH2
8.153 8.149 8.183 8.388 8.471 8.297 8.480 8.327 8.315 8.288 8.334 8.499 8.480 8.560 8.758 8.845 S-758 8.626 8.508 8.162 8.216 8.173 8.163 8.079 8.059 8.580
2.332 2.407 2.425 2.473 2.381 2.308 2.341 2.235 2.079 2.239 2.264 2.476 2.412 2.141 2.736 2.766 2.767 2.938 3.020 2.385 2.394 2.352 2.018 I.984 2.015 2.162
0.230 0.219 0.143 0.189 0.268 0.334 0.217 0.379 0.43 f 0.273 0.260 0.388 0.348 0.124 0.318 0.301 0.259 0.311 0.322 0.288 0.260 0.291 0.314 0.287 0.271 0.383
0.043 0.024 0.003 0.038 0.013 0.013 0.019 0.015 0.03 7 0.014 0.01 I 0.023 0.014 0.013 0.005 0.005 0.020 0.027 0.011 0.030 0.026 0.022 0.017 0.007 0.014 0.032
CH3
Cl
CH3
NO2
Cl CI
CHa
NO2
NO2
(CH312CO
NJ% Cl
CC
I
CIzCH2 O(CH,CW,O
CH3
NO2
s2c
Cl
CHs
OH
NH2
Cl
CHx
NH,
Br
Cl-I3
NH2
NO2
CH3
TABLE VALUES
CH&N Cl&H2 O(CH,CHz)zO C12CH2 CHjOH CH&N CH3NOz CHjOH C12CH2 CL& O(CHaCH&O
3 OF E,&(in
Hz)
x
E 12
I CHO OCHB N(CHdz
0.37 0.18 0.74 0.84 0.07 0.49
CH3
CP D Average
FORDIFFERENTSUBSTITUENTS
E 13
-0.24 -0.06 -0.36 -0.37 -0.13 -0.26
E 14
E 15
E 23
E 24
-00.23 -0.04 -0.25 - 0.27 -0.08 -0.18
0.50 0.37 1.36 1.38 0.48 0.87
-0.09 -0.09 -0.21 - 0.27 -0.03 -0.02
0.37 -0.12 0.38 0.38 0.12 0.28
of the four set of values of ref. 2.
In Tables 4 and 5- are shown the three calculated Jztz of substituted benzaldehydes and methyl benzenes together with the experimental values of Jxyz obtained as an average of the different experimental parameters listed on Tybles 1 &d 2.
401 TABLE
4
CALCULATED
AND
OBSERVED
COUPLING
CONSTANTS
(ill %)a
FOR BENZALDEHYDES
x
Y
z
Jz=(caZc)
Jfz’(exp)
J~~z(caZc)
J~~z(exp>
J:z+aZc)
Jam=
CHO CHO NOz
Cl NOz CHO CHO OH Cl OCI-& OH CHO CHO CHO CHO NO2 0CH3 CI
Cl NOz Cl OH CHO CHO CHO OH OH Cl Bt NO2 CHO OCH3 N(CH,)z
8.21 fO.10 8.45 8.76 8.88 8.19 8.21 8.27 8.19 8.69 8.57 8.57 8.88 8.26 8.27 8.56
8.45f0.05 8.56 8.75 9.01 8.13 8.22 8.21 8.59 8.90 8.89 8-91 9.22 8.64 8.60 8.96
1.87iO.10 2.08 2.29 2.75 1.82 1.77 1.77 2.30 3.01 2.55 2.42 2.70 1.91 2.26 2.38
1.96f0.05 2.19 2.38 2.79 1.91 1.92 1.92 2.24 3.07 2.69 2.54 2.84 1.72 2.25 2.51
0.29f0.10 0.37 0.33 0.31 0.25 0.29 0.15 0.25 0.25 0.27 0.22 0.3 1 0.31 0.15 0.20
0.28&0.05 0.37 0.33 0.27 0.34 0.35 0.17 0.25 0.45 0.38 0.32 0.33 0.41 0.30 0.20
NO2
OH Cl OCHJ CHO OH OH OH OH OH CHO CHO
J The estimated error in each column is given by the first row. TABLE
5
CALCULATED
AND
OBSERVED
COUPLING
CONSTANTS
FOR
METHYL
BENZENES
(ill Hz)O
X
Y
Z
J~~z(caZc)
Jazz
J~~z(ca/c)
Jzz(exp)
J:,Yz(caZc)
Jfzz(exp)
CH3 CH3 CH3 CHs Cl Cl NI-IZ NH2 CH3 CH, NH2 NH,
I I Cl NO2 CHJ CHJ Cl Br Cl NO, CH3 NO2
NH2 NOr
8.00f0.10 8.34 8.41 8.34 8.82 8.63 8.07 8.01 8.10 8.03 8.36 8.00
8.16f0.05 8.43 8.37 8.49 iO.06 8.79 8.57 8.18 8.10 8.32 8.31 8.56 8.58
2.41 +O.lO 2.28 2.26 2.32 2.55 2.86 1.82 1.82 2.11 2.17 1.97 1.88
2.39f0.05 2.43 2.29 2.44f0.06 2.76 2.98 2.38 2.01 2.08 2.25 2.14 2.16
0.X6&0.10 0.24 0.29 0.33 0.29 0.23 0.21 0.16 0.25 0.29 0.16 0.25
0.20+0.05 0.23 0.31 0.37f0.06 0.29 0.32 0.28 0.29 0.43 0.27 0.12 0.38
NO2
NO2 NOz OH CHJ CH3
Cl Cl I CHJ
’ Except when indicated,the estimatederror in each column is given by the first row.
With the exception of 3 out of 15 substances there is a very good correlation for the benzaldehydes between all the calculated and the experimental J2Jz values. The correlation is observed for those substances that do not have internal hydrogen
bond or strong interacting groups2.
In the twelve methyl
benzenes
the correlation
is also good
for the .T~~z
values and for all but three of the Jr:” and Jczz parameters. Deviations of a similar order of magnitude were found previously2 for substituents that can interact between themselves. These deviations can be due to the
402 fact that the effects which each one of the substituents has on the electronic structure of the other substituent can modify the inductive and mesomeric character that each substituent has as a monosubstituent”. It has recently been found” that in the cases for which additivity holds, the Jzz values can also be calculated by means of a regression function in which the Jam’ values are correlated with a linear combination of different substituent parameters’ ‘* ’ 3.
REFERENCES 1 D. G. KOWALEWSKI, R. BUITRA~O AND R. YOMMI, J. Mol. Structure, 11 (1971) 195. 2 S. CA~TELLANO AND R. KOSTELNIK, Terruhedron Lerr., 55 (1967) 5211 and references cited
therein. 3 D. G. DE KOWALEWSKI AND S. CAZXELLANO,Mel Phys_, 16 (1969) 567. 4 H. B. EVANS JR, A. R. TARPLEY AND 3. H. GOLDSTEIN, 3. Phys. Chem., 72 (1968) 2552 and references cited therein. 5 V. J. KOWALJZWSKI,Progress in iVdear Magnetic Resonance Spectroscopy, Vol. 5, Pergamon
Press, 1968, p. 1. 6 A. B. BOTHNER-BY AND S. CASTELLANO,LAOCN 3, Mellon Institute, Pittsburgh, Pa., (1966). 7 J. A. POPLE, G. SCHNEIDERAND H. J. BERSTEM, Can. J. C’enz., 35 (1957) 1060. 8 J. MARTIN AND B. P. DAILEY, J. Chem. Phys., 36 (1962) 2442. 9 D. G. DE KOWALEWSKI AND V. J. KOWALEWSKI, Mot. Phys., 9 (1965) 319, 331. 10 J. M. READ, R. E. MAYO AND J. H. GOLDSTEIN, J. Mol. Specrrusc., 21 (1966) 235. 11 C. C. SWAIN AND E. C. LUPTON JR, J. Amer. Chem. Sot_, 90 (1968) 4328. 12 D. G. DE KOWALEWSKI AND S. ESAIN, unpublished redts, 1972. 13 M. J. DEWAR, R. GOLDEN AND J. M. HARRIS, J. Amer. Chern. SOL, 93 (1971) 4187.
@ EISeVier Scientific Publishing
Company,
Amsterdam
- Printed in The Netherlands
SUBSTITUENT EFFECTS ON THE PROTON SPIN-SPIN COUPLING BENZENES WITH SIDE-CHAIN INTERACTING GROUPS*
OF
D. G. DE KOWALEWSKl
Departanzento de Fisica, Fact&ad de Ciencias Exactas y Natwales, Consejo National de hvestigaciones, Buenos Aires (Argentina)
R. BUITRAGO
AND
Ciudad Uniuersitaria and
R. YOMMI
Departamento de Fisica Universidad de! Litoral, Santa Fe (Argentina) (Received
5 December
1972)
ABSTRACT
Sixty MHz NMR proton spectra of 15 2,4_substituted benzaldehydes and , I2 methylbenzenes dissolved in different solvents have been accurately analyzed. Substituent effects on the coupling constants have been determined and have been found to be additive in those trisubstituted compounds where there are neither I internal hydrogen bonds or strong interacting groups present.
INTRODUCTION
It was recently established’ that addivity relationships exist for substituent effects on the proton-proton coupling constants of trisubstituted benzenes. Due to the short-range effect of the tr electrons on Jnn, it was also possible to verify additivity relations in benzenes with more than one substituent”2-4, but some experimental results on ortho-disubstituted benzenes2 show that the additivity rule fails in cases of strongly interacting ortho substituents (OH, NOz; N02, NO2 ; CI, NO,). The ABC spectra of 37 benzenes with side-chain interacting groups (CHO, CHs) were analyzed in a similar way to that described in a previous work’ and the coupling constants were determined. The rest&s obtained with the additivity relations were then compared with those obtained from experimental data. * This work was sponsored
in part by the Consejo National
de Investigaciones
(Argentina).
396 EXPERIMENTAL The experimental procedure and the method of analysis follows the outlines the previous paper’ with addition that a second and eventuahy a third r.f. field (supplied as field modulation by two auxiliary audio osciliators) were applied to decouple each one of the resonances of the side-chain groups present in the molecule. As an example Fig. lb shows the methyl irradiated spectra of the Zbromo, 6-methylani~ine in methanol solution _ For those spectra in which the observed line broadening was expected to be due to a second side-chain long-range coupling a third r.f. field was applied. This was the case for the 2-chloro, 4-dimethylaminobenzaldehyde (Fig. 2~) and for all of the methoxy~~dehydes (Fig. 3b). Eight solvents were used (methanol, p-dioxane, Ccl,. CS, , dichloromethane, acetone, acetonitrile and nitromethane) until spectral lines of a haffwidth of 0.3 Hz were obtained. Sometimes a good solvent with Iow-viscosity had to be abandoned because its resonance was near that of the group to be irradiated of
“1
L....~....r....l....I....r....l....~...., -
75
m
(6
90
55
603
5
a
I-...,....,
um
n
ltMHZ
Fig. 1. (a) Frequency sweep proton 60 MHz spectrum of Zbromo, &methyIaniline in methanol solution; (b) Ring protons spectrum of the same substance recorded with simultaneous irradiation at the mean frequency of the CI-& group.
397
CHO
b)
Fig. 2. (a) Frequency sweep proton 60 MHz spectra of 2-chloro, Cdimethylamine benzaldehyde in acetonitrile solution; (b) The same spectra obtained when a second r-f. field is set on the N(CH& resonance: (c) Spectra obtained when the N(CHs)z and CHO resonances are strongly irradiated.
398
cno
I
d H2
Fig. 3. (a) Frequency sweep 60 MHz spectra of 3,4-dimethoxybenzaldehyde in acetonitrile solution; (b) Double irradiation experiments performed on the same solution_ The left side of the spectra was performed with the r.f. centered at the (OCH& resonance. The right side of the spectra was recorded while irradiating simultaneously the CHO and (OCH& resonances.
(ca. 10 Hz). This is one of the reasons why five out of the 27 substances were analyzed in only one solvent. All compounds used in this work were of commercial origin. In some cases, lines were identified as arising from impurities by the Indor technique5. Samples were measured as solutions of maximum possible concentration (IO-20 % w/w) in different solvents, with about 10 percent hexamethyldisiloxane as internal reference. All samples were degassed and seaIed under vacuum.
RESULTS
The ABC spectra of the ring protons of the trisubstituted benzenes were analyzed by means of the computer program LAOCN36. The signs of the coupling constants between the ring protons have been determined to be positive by many workers using various methods 7p8. Therefore, all the ring coupling constants were assumed to be positive. Table 1 gives the coupling constants of substituted benzaldehydes obtained from the decoupled spectra of substituted benzaIdehydes in different solvents,
399 together with their calculated root mean square (RMS) error. It can be seen that the precision of the .J values is much better than that in a previous work on benzaldehydesg where only the non-decoupled spectra of the substance, in one solvent, were calculated. Table 2 gives the coupling constants of methyl benzenes in different solvents. With the exception of two out of 57 solutions the maximum difference in the J values obtained for the same substance in different solvents is L-O.06 HZ. Table 3 shows the Es,, values corresponding to I, CHO, N(CH,),, CH, and Cl calculated from the monosubstituted benzene data’ and from the best available benzene Ji valueslo. Substituting into eqns. (l)-(3) of ref. 1 the vaIues of E,& for the different substituents and the values of Ji corresponding to benzene, the values of the proton-proton coupling constants of the substituted benzaidehydes and methyl benzenes can be calculated. TABLE
1
PROTON-PROTON
COUPLING
CONSTANTS
(in Hz)
OF BENZALDEHYDES
IN DIFFERENT
SOLVENTS
x
Y
z
Solvent
J ,t
J 24
J 14
RMS
CHO
Cl
Cl
CHO CHO
OCHJ OH
OCH, OH
OH
CHO
OH
CHO
NO,
NO+
CI,C CHJCOCHB CH&N CH&N CH3COCH3 CH30H CHaOH CH3CN CH,COCH, CHJZN
CHO
Cl
NWW,
OH
CHO
Cl
OH
CHO
Br
NO2
CHO
Cl
NOz
CHO
OH
OH
OH
CHO
Cl
Cl
CHO
OCHs
OCHJ
CHO
OH OH
NO2
CHO
CHO
NO2
8.387 8.514 8.603 8.594 8.605 8.579 8.91 I 8.891 8.516 8.602 8.973 8.941 8.952 8.894 8.83 I 8.928 8.900 8.763 8.788 8.686 8.998 9.018 8.200 8.066 8.233 8.202 8.184 8.205 8.244 8.637 9.224
I.942 1.982 2.25 1 2.262 2.247 2.222 3.060 3.076 2.189 2.197 2.523 2.496 2.690 2.712 2.666 2.566 2.520 2.388 2.365 2.392 2.776 2.799 1.915 1.908 1.921 1.911 1.916 1.916 1.916 1.722 2.838
0.336 0.224 0.301 0.274 0.248 0.239 0.432 0.473 0.365 0.371 0.179 0.213 0.377 0.379 0.388 0.346 0.290 0.389 0.337 0.270 0.286 0.253 0.366 0.310 0.361 0.332 0.180 0.199 0.138 0.410 0.327
0.006 0.013 0.023 0.006 0.029 0.010 O.‘olS 0.013 0.027 0.018 0.029 0.024 0.009 0.020 0.014 0.010 0.019 0.012 0.015 0.020 0.015 0.005 0.035 0.029 0.011 0.007 0.013 0.006 0.003 0.009 0.016
O(CHKHt)tO CH3CN CHsCN 0(CH&H2)20 CH,COCH, CH3COCH3 O(CHzCW,O CH3COCH3 CH$ZN O(CHrCW,O CH3COCHB CH3CN CHsCOCH3 O(CJ&<=H2)20
CH3COCH3 CH&N CH3COCH3 CHJCN CH30H O~CHzCH&O O(CHzCHd20
TABLE
2
PROTON-PROTON
COUPLING
CONSTANTS
(ill Hz)
OF METHYL
BENZENES
IN DIFFERENT
SOLVENTS
X
Y
2
Soiuent
J12
J24
Jl.%
RMS
CH3
I
NH2
CHBOH CHsCN
CHs
I
NO2
CH3
Cl
NO2
%(;H,CH,),O Cf 2CH2 CHaCN Cl& tCH,)tCO CHJZN c&c CIICH2
8.153 8.149 8.183 8.388 8.471 8.297 8.480 8.327 8.315 8.288 8.334 8.499 8.480 8.560 8.758 8.845 S-758 8.626 8.508 8.162 8.216 8.173 8.163 8.079 8.059 8.580
2.332 2.407 2.425 2.473 2.381 2.308 2.341 2.235 2.079 2.239 2.264 2.476 2.412 2.141 2.736 2.766 2.767 2.938 3.020 2.385 2.394 2.352 2.018 I.984 2.015 2.162
0.230 0.219 0.143 0.189 0.268 0.334 0.217 0.379 0.43 f 0.273 0.260 0.388 0.348 0.124 0.318 0.301 0.259 0.311 0.322 0.288 0.260 0.291 0.314 0.287 0.271 0.383
0.043 0.024 0.003 0.038 0.013 0.013 0.019 0.015 0.03 7 0.014 0.01 I 0.023 0.014 0.013 0.005 0.005 0.020 0.027 0.011 0.030 0.026 0.022 0.017 0.007 0.014 0.032
CH3
Cl
CH3
NO2
Cl CI
CHa
NO2
NO2
(CH312CO
NJ% Cl
CC
I
CIzCH2 O(CH,CW,O
CH3
NO2
s2c
Cl
CHs
OH
NH2
Cl
CHx
NH,
Br
Cl-I3
NH2
NO2
CH3
TABLE VALUES
CH&N Cl&H2 O(CH,CHz)zO C12CH2 CHjOH CH&N CH3NOz CHjOH C12CH2 CL& O(CHaCH&O
3 OF E,&(in
Hz)
x
E 12
I CHO OCHB N(CHdz
0.37 0.18 0.74 0.84 0.07 0.49
CH3
CP D Average
FORDIFFERENTSUBSTITUENTS
E 13
-0.24 -0.06 -0.36 -0.37 -0.13 -0.26
E 14
E 15
E 23
E 24
-00.23 -0.04 -0.25 - 0.27 -0.08 -0.18
0.50 0.37 1.36 1.38 0.48 0.87
-0.09 -0.09 -0.21 - 0.27 -0.03 -0.02
0.37 -0.12 0.38 0.38 0.12 0.28
of the four set of values of ref. 2.
In Tables 4 and 5- are shown the three calculated Jztz of substituted benzaldehydes and methyl benzenes together with the experimental values of Jxyz obtained as an average of the different experimental parameters listed on Tybles 1 &d 2.
401 TABLE
4
CALCULATED
AND
OBSERVED
COUPLING
CONSTANTS
(ill %)a
FOR BENZALDEHYDES
x
Y
z
Jz=(caZc)
Jfz’(exp)
J~~z(caZc)
J~~z(exp>
J:z+aZc)
Jam=
CHO CHO NOz
Cl NOz CHO CHO OH Cl OCI-& OH CHO CHO CHO CHO NO2 0CH3 CI
Cl NOz Cl OH CHO CHO CHO OH OH Cl Bt NO2 CHO OCH3 N(CH,)z
8.21 fO.10 8.45 8.76 8.88 8.19 8.21 8.27 8.19 8.69 8.57 8.57 8.88 8.26 8.27 8.56
8.45f0.05 8.56 8.75 9.01 8.13 8.22 8.21 8.59 8.90 8.89 8-91 9.22 8.64 8.60 8.96
1.87iO.10 2.08 2.29 2.75 1.82 1.77 1.77 2.30 3.01 2.55 2.42 2.70 1.91 2.26 2.38
1.96f0.05 2.19 2.38 2.79 1.91 1.92 1.92 2.24 3.07 2.69 2.54 2.84 1.72 2.25 2.51
0.29f0.10 0.37 0.33 0.31 0.25 0.29 0.15 0.25 0.25 0.27 0.22 0.3 1 0.31 0.15 0.20
0.28&0.05 0.37 0.33 0.27 0.34 0.35 0.17 0.25 0.45 0.38 0.32 0.33 0.41 0.30 0.20
NO2
OH Cl OCHJ CHO OH OH OH OH OH CHO CHO
J The estimated error in each column is given by the first row. TABLE
5
CALCULATED
AND
OBSERVED
COUPLING
CONSTANTS
FOR
METHYL
BENZENES
(ill Hz)O
X
Y
Z
J~~z(caZc)
Jazz
J~~z(ca/c)
Jzz(exp)
J:,Yz(caZc)
Jfzz(exp)
CH3 CH3 CH3 CHs Cl Cl NI-IZ NH2 CH3 CH, NH2 NH,
I I Cl NO2 CHJ CHJ Cl Br Cl NO, CH3 NO2
NH2 NOr
8.00f0.10 8.34 8.41 8.34 8.82 8.63 8.07 8.01 8.10 8.03 8.36 8.00
8.16f0.05 8.43 8.37 8.49 iO.06 8.79 8.57 8.18 8.10 8.32 8.31 8.56 8.58
2.41 +O.lO 2.28 2.26 2.32 2.55 2.86 1.82 1.82 2.11 2.17 1.97 1.88
2.39f0.05 2.43 2.29 2.44f0.06 2.76 2.98 2.38 2.01 2.08 2.25 2.14 2.16
0.X6&0.10 0.24 0.29 0.33 0.29 0.23 0.21 0.16 0.25 0.29 0.16 0.25
0.20+0.05 0.23 0.31 0.37f0.06 0.29 0.32 0.28 0.29 0.43 0.27 0.12 0.38
NO2
NO2 NOz OH CHJ CH3
Cl Cl I CHJ
’ Except when indicated,the estimatederror in each column is given by the first row.
With the exception of 3 out of 15 substances there is a very good correlation for the benzaldehydes between all the calculated and the experimental J2Jz values. The correlation is observed for those substances that do not have internal hydrogen
bond or strong interacting groups2.
In the twelve methyl
benzenes
the correlation
is also good
for the .T~~z
values and for all but three of the Jr:” and Jczz parameters. Deviations of a similar order of magnitude were found previously2 for substituents that can interact between themselves. These deviations can be due to the
402 fact that the effects which each one of the substituents has on the electronic structure of the other substituent can modify the inductive and mesomeric character that each substituent has as a monosubstituent”. It has recently been found” that in the cases for which additivity holds, the Jzz values can also be calculated by means of a regression function in which the Jam’ values are correlated with a linear combination of different substituent parameters’ ‘* ’ 3.
REFERENCES 1 D. G. KOWALEWSKI, R. BUITRA~O AND R. YOMMI, J. Mol. Structure, 11 (1971) 195. 2 S. CA~TELLANO AND R. KOSTELNIK, Terruhedron Lerr., 55 (1967) 5211 and references cited
therein. 3 D. G. DE KOWALEWSKI AND S. CAZXELLANO,Mel Phys_, 16 (1969) 567. 4 H. B. EVANS JR, A. R. TARPLEY AND 3. H. GOLDSTEIN, 3. Phys. Chem., 72 (1968) 2552 and references cited therein. 5 V. J. KOWALJZWSKI,Progress in iVdear Magnetic Resonance Spectroscopy, Vol. 5, Pergamon
Press, 1968, p. 1. 6 A. B. BOTHNER-BY AND S. CASTELLANO,LAOCN 3, Mellon Institute, Pittsburgh, Pa., (1966). 7 J. A. POPLE, G. SCHNEIDERAND H. J. BERSTEM, Can. J. C’enz., 35 (1957) 1060. 8 J. MARTIN AND B. P. DAILEY, J. Chem. Phys., 36 (1962) 2442. 9 D. G. DE KOWALEWSKI AND V. J. KOWALEWSKI, Mot. Phys., 9 (1965) 319, 331. 10 J. M. READ, R. E. MAYO AND J. H. GOLDSTEIN, J. Mol. Specrrusc., 21 (1966) 235. 11 C. C. SWAIN AND E. C. LUPTON JR, J. Amer. Chem. Sot_, 90 (1968) 4328. 12 D. G. DE KOWALEWSKI AND S. ESAIN, unpublished redts, 1972. 13 M. J. DEWAR, R. GOLDEN AND J. M. HARRIS, J. Amer. Chern. SOL, 93 (1971) 4187.