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Correlation of carbonyl frequencies of aromatic derivatives with their nonaromatic analogues
Spctrochimica Acta, Vol. MA, pp. 1159 to 1163. Pergamon Press Ltd., 1978. Printed in Great Britain
Correlation of carbonyl frequencies of aromatic derivatives with their nonaromatic analogus EDWARD
N.
PETERS
Union Carbide Corporation, Chemicals and Plastics, One River Road, Bound Brook, NJ 08805, U.S.A. (Receiued 11 Jury 1977) Abstract-A linear free energy relationship, v = v. + py+, with group constants, y+, was defined. The group constants are characteristic of the inductive and resonance effects of aryl and hydrogen groups. The use of group constants allows the direct correlation of carbonyl stretching frequencies of aromatic derivatives with their corresponding nonaromatic analogues in which the aryl group has been replaced by a hydrogen group.
WTRODUC’IION
Infrared frequency shills of aromatic compounds have been correlated by a linear free energy relationship [l].
(1)
v=vcJ+pa
In Equation (l), v is the observed frequency of the substituted derivative and v. is the frequency of the unsubstituted derivative. The substituent constant, a, is characteristic of the inductive effects of the substituent on the aromatic group. The p value is an indication of the effect that substituents have on the frequency. In addition to o constants [2-4-J, CT+constants which are characteristic of inductive and resonance effects have been used in Equation (1) [5,6]. Recently a linear free energy relationship was defined which used group constants, Y+, and allowed the direct correlation of rates of nonaromatic with aromatic derivatives [A. The y+ constants are characteristic of an entire group (aryl or hydrogen). The y+ constants for aryl groups are ihe same as the u+ constants for
1740 -
the substituent on that aryl group. The y+ constant for a hydrogen group was determined to be 2.53. For the correlation of carbonyl frequencies of aryl derivatives (2) with their corresponding non-aryl derivatives (3), a relationship with y+ constants
/0 \ i-*
(2)
Y-
0
H- e -A
(3)
similar to Equation (1) is proposed (4).
v=vg+py+
(4)
EXPERIMENTAL
Carbonyl frequencies in dilute solutions of carbon tetrachloride or chloroform were taken from the literature if suitable data was available. The carbonyl frequency for formaldehyde (0.05% in carbon tetrachloride) was determined on a Beckman IR 4240 snectrouhotometer and found . to be 1733 cm-r.
!? R-C-H
1730 T E 0 c 1720 s s ?! tA
- 2.0
I
I
I
I
I
-1.0
0
1.0
2.0
3.0
Y+ Fig. 1. 1159
EDWARD N. PEIXRS
1160
1720 T 1
P IL
1710-
1700 -
1690 -
1660 -
I670 -2.0
1 -1.0
I 0
Y+
I 1.0
I 2.0
1 3.0
Fig. 2.
IL
1670
(
1660
F&. 3.
I
1705
1660 1675
, -2.0
I - 1.0
I 0
7+
Fig. 4.
I I.0
1 2.0
I 3s
Correlation of carbonyl frequencies of aromatic derivatives with their nonaromatic analogues
1660 I -1.0
- 2.0
I 0
I 1.0
Y+ Fig. 5.
1790 0 R-&OH
1760 -
TE "
1770 -
E a 5
1760 -
e IL 1750 -
-2.0
-1.0
Fig. 6.
1735 -
0 R-k-OEt
1730 '., T 5
1725 -
E 5 g 1720 a It
-2.0
- 1.0
0
Y+
Fig. 7.
I 2.0
1 3.1
1161
1162
EDWARD N.
PETERS :
1690 ‘.
.
/
3
0
A
:
l66p
1650 C ,
Fig.8. RESULTS The carbonyl frequency of formaldehyde was correlated with the carbonyl frequencies of substituted benzaldehydes [8] by the use of y+ constants as shown in Fig. 1. Similarly the carbonyl frequency of acetaldehyde [9] was correlated with substituted acetophenones [lo] in Fig. 2, benzaldehyde [9] with substituted benzophenones [4] in Fig. 3, acrolein [ 1l] with substituted cinnamaldehydes [8] in Fig. 4, cinnamaldehyde [12] with substituted trans-chalcones [13] in Fig. 5, monomeric formic acid [14] with substituted benzoic acids [15] in Fig. 6, ethyl formate [3] with substituted ethyl benzoates [2] in Fig. 7, and N-methyl formamide [16] with N-methyl benzamides [3] in Fig. 8. DISCUSSION
The influence of changes in the structure of the groups attached to the carbonyl group on its frequency depends on several factors [lo, 17,181. However, in the absence of special influences such as ring strain or
hydrogen bonding the main factors which affect the frequency are the inductive and resonance effects of the groups attached to the carbonyl group [19]. The y+ constants are a function of inductive and resonance effects. Hence, a correlation between the carbonyl frequencies of aromatic and nonaromatic derivatives has a theoretical basis. In correlating such a diverse assortment of data, one might expect deviations due to the fact that the carbonyl frequencies were determined in several different laboratories and inaccuracy of the shifts [20] ; however, rough correlations were obtained. The results of a statistical evaluation of the correlations of carbonyl frequencies with y+ constants are summarized in Table 1. For comparison, the data for correlating only the substituted aromatic derivatives with o+ constants are included. The average standard deviation for the v - y+ and v - u+ correlations are 0.87 and 0.86, respectively. The average correlation coefficients are 0.965 and 0.970, respectively. Clearly Equation (4) is generally useful in correlating
Table 1. Correlation of carbonyl frequencies* y+ correlation System formaldehyde+benzaldehydes acetaldehyde-acetophenones benzaldehydebenzophenones acrolein-cinnamaldehydes cinnamaldehyde-chalcones formic acid-benzoic acids ethyl formate-ethyl benzoates N-methyl formamideN-methyl benzamides
0+ correlation
P
SD**
l-t
P
SD**
l-V
8.81 14.76 12.61 6.14 3.92 14.42 6.99
0.72 1.05 0.90 0.35 0.83 1.27 0.87
0.975 0.983 0.988 0.996 0.858 0.981 0.963
7.56 10.51 9.15 6.50 5.44 9.13 9.47
0.73 0.61 0.66 0.60 0.99 0.49 1.09
0.969 0.990 0.990 0.992 0.889 0.994 0.974
9.46
0.98
0.974
11.58
1.70
0.960
* Computer calculated using least squares analysis. ** Standard deviation. t Correlation coefficient.
Correlationof carbonyl fkquencies of aromaticderivativeswith their nonaromaticanalogues carbonyl frequencies. However, one should be carehd in applying this technique to correlating other i.r. frequencies until the potential and limitations of Equation (4) has been studied. For example, one dear not get a correlation between y+ for methyl [21] and carbonyl frequencies. REFERENCES
1163
E. N. Pmms, J. Am. Chem. Sot. -5627 (1976). 8 I. N. JUCHNOVSKI, Capt. red. Bulgar. Xl, 33 (1%7). 9 L. J. BELLAMY and R. J. PACE,Speckrochim.Acta 19,
rl
1831(1%3). [lo] R. N. JONES, W. F. FORBES and W. A. MUELLER, Can.
J. C/&m. 35,5lM (1957). 11 Y. ON0 and Y. UBDA,Chem.Pharm.Bull. 22,390 (1974). 12 W. P. HAYSSand C. J. Tnaro~g SpectrocJ~imActa E3 24A, 323 (1968). [13] :9kiT~~ and D. W. BoYKIN,J. Org. Chem. 36,759
14 J. K. WILMSH~RST, J. Chem. Phys. 25,478 (1956). 1 H. H. Jmi, Chem.Rev. 53,191(1953). 2 H. W. THOMPSON, R. W. NEEDHAM and D. A. JAM~SON, 15 M. ST.C. FLETT,Trans. Faraday Sot. 44,767 (1948). Spectrochim.Acta 9,208 (1957) and K. V. RAMIAH, J. Mol. Spectrosc. I116 V. V. CHALAPATHI [3] H. W. THOMPSON and D. A. JAM@SON, SpectrocJh. M, 444 (lf=). Acta 13,236 (1958). 17j J. 0. HALPORD, J. Chem. Phys. 24,830 (1956). [4] N. FUS~N,M. L J~SIENand E. M. SHBLIDN, J. Am. E183 J. OVEREND and J. R. SCHERER,Specrrochim.Ada Chem.Sot. 76,2526 (1954). la, 773 (1960) [5] C. N. R. RAOand R. VENKATARAOHAVAN, Can. J. I’191 _ - R. C. LORD and F. A. MILLER, AI& . . Spectrosc. Chem. 39.1757 (1961). 10, 115 (1956). [6-j H. C. BROWNand Y. OKAMOTO, J. Am. Chem. Sot. [20] M. LIIER,Spectrochim.Ada 23A, 139 (1%7). 80,4979 (1958). [21] E. N. Pmm, J. Org. Gem. 42,1419 (1977).
El
Correlation of carbonyl frequencies of aromatic derivatives with their nonaromatic analogus EDWARD
N.
PETERS
Union Carbide Corporation, Chemicals and Plastics, One River Road, Bound Brook, NJ 08805, U.S.A. (Receiued 11 Jury 1977) Abstract-A linear free energy relationship, v = v. + py+, with group constants, y+, was defined. The group constants are characteristic of the inductive and resonance effects of aryl and hydrogen groups. The use of group constants allows the direct correlation of carbonyl stretching frequencies of aromatic derivatives with their corresponding nonaromatic analogues in which the aryl group has been replaced by a hydrogen group.
WTRODUC’IION
Infrared frequency shills of aromatic compounds have been correlated by a linear free energy relationship [l].
(1)
v=vcJ+pa
In Equation (l), v is the observed frequency of the substituted derivative and v. is the frequency of the unsubstituted derivative. The substituent constant, a, is characteristic of the inductive effects of the substituent on the aromatic group. The p value is an indication of the effect that substituents have on the frequency. In addition to o constants [2-4-J, CT+constants which are characteristic of inductive and resonance effects have been used in Equation (1) [5,6]. Recently a linear free energy relationship was defined which used group constants, Y+, and allowed the direct correlation of rates of nonaromatic with aromatic derivatives [A. The y+ constants are characteristic of an entire group (aryl or hydrogen). The y+ constants for aryl groups are ihe same as the u+ constants for
1740 -
the substituent on that aryl group. The y+ constant for a hydrogen group was determined to be 2.53. For the correlation of carbonyl frequencies of aryl derivatives (2) with their corresponding non-aryl derivatives (3), a relationship with y+ constants
/0 \ i-*
(2)
Y-
0
H- e -A
(3)
similar to Equation (1) is proposed (4).
v=vg+py+
(4)
EXPERIMENTAL
Carbonyl frequencies in dilute solutions of carbon tetrachloride or chloroform were taken from the literature if suitable data was available. The carbonyl frequency for formaldehyde (0.05% in carbon tetrachloride) was determined on a Beckman IR 4240 snectrouhotometer and found . to be 1733 cm-r.
!? R-C-H
1730 T E 0 c 1720 s s ?! tA
- 2.0
I
I
I
I
I
-1.0
0
1.0
2.0
3.0
Y+ Fig. 1. 1159
EDWARD N. PEIXRS
1160
1720 T 1
P IL
1710-
1700 -
1690 -
1660 -
I670 -2.0
1 -1.0
I 0
Y+
I 1.0
I 2.0
1 3.0
Fig. 2.
IL
1670
(
1660
F&. 3.
I
1705
1660 1675
, -2.0
I - 1.0
I 0
7+
Fig. 4.
I I.0
1 2.0
I 3s
Correlation of carbonyl frequencies of aromatic derivatives with their nonaromatic analogues
1660 I -1.0
- 2.0
I 0
I 1.0
Y+ Fig. 5.
1790 0 R-&OH
1760 -
TE "
1770 -
E a 5
1760 -
e IL 1750 -
-2.0
-1.0
Fig. 6.
1735 -
0 R-k-OEt
1730 '., T 5
1725 -
E 5 g 1720 a It
-2.0
- 1.0
0
Y+
Fig. 7.
I 2.0
1 3.1
1161
1162
EDWARD N.
PETERS :
1690 ‘.
.
/
3
0
A
:
l66p
1650 C ,
Fig.8. RESULTS The carbonyl frequency of formaldehyde was correlated with the carbonyl frequencies of substituted benzaldehydes [8] by the use of y+ constants as shown in Fig. 1. Similarly the carbonyl frequency of acetaldehyde [9] was correlated with substituted acetophenones [lo] in Fig. 2, benzaldehyde [9] with substituted benzophenones [4] in Fig. 3, acrolein [ 1l] with substituted cinnamaldehydes [8] in Fig. 4, cinnamaldehyde [12] with substituted trans-chalcones [13] in Fig. 5, monomeric formic acid [14] with substituted benzoic acids [15] in Fig. 6, ethyl formate [3] with substituted ethyl benzoates [2] in Fig. 7, and N-methyl formamide [16] with N-methyl benzamides [3] in Fig. 8. DISCUSSION
The influence of changes in the structure of the groups attached to the carbonyl group on its frequency depends on several factors [lo, 17,181. However, in the absence of special influences such as ring strain or
hydrogen bonding the main factors which affect the frequency are the inductive and resonance effects of the groups attached to the carbonyl group [19]. The y+ constants are a function of inductive and resonance effects. Hence, a correlation between the carbonyl frequencies of aromatic and nonaromatic derivatives has a theoretical basis. In correlating such a diverse assortment of data, one might expect deviations due to the fact that the carbonyl frequencies were determined in several different laboratories and inaccuracy of the shifts [20] ; however, rough correlations were obtained. The results of a statistical evaluation of the correlations of carbonyl frequencies with y+ constants are summarized in Table 1. For comparison, the data for correlating only the substituted aromatic derivatives with o+ constants are included. The average standard deviation for the v - y+ and v - u+ correlations are 0.87 and 0.86, respectively. The average correlation coefficients are 0.965 and 0.970, respectively. Clearly Equation (4) is generally useful in correlating
Table 1. Correlation of carbonyl frequencies* y+ correlation System formaldehyde+benzaldehydes acetaldehyde-acetophenones benzaldehydebenzophenones acrolein-cinnamaldehydes cinnamaldehyde-chalcones formic acid-benzoic acids ethyl formate-ethyl benzoates N-methyl formamideN-methyl benzamides
0+ correlation
P
SD**
l-t
P
SD**
l-V
8.81 14.76 12.61 6.14 3.92 14.42 6.99
0.72 1.05 0.90 0.35 0.83 1.27 0.87
0.975 0.983 0.988 0.996 0.858 0.981 0.963
7.56 10.51 9.15 6.50 5.44 9.13 9.47
0.73 0.61 0.66 0.60 0.99 0.49 1.09
0.969 0.990 0.990 0.992 0.889 0.994 0.974
9.46
0.98
0.974
11.58
1.70
0.960
* Computer calculated using least squares analysis. ** Standard deviation. t Correlation coefficient.
Correlationof carbonyl fkquencies of aromaticderivativeswith their nonaromaticanalogues carbonyl frequencies. However, one should be carehd in applying this technique to correlating other i.r. frequencies until the potential and limitations of Equation (4) has been studied. For example, one dear not get a correlation between y+ for methyl [21] and carbonyl frequencies. REFERENCES
1163
E. N. Pmms, J. Am. Chem. Sot. -5627 (1976). 8 I. N. JUCHNOVSKI, Capt. red. Bulgar. Xl, 33 (1%7). 9 L. J. BELLAMY and R. J. PACE,Speckrochim.Acta 19,
rl
1831(1%3). [lo] R. N. JONES, W. F. FORBES and W. A. MUELLER, Can.
J. C/&m. 35,5lM (1957). 11 Y. ON0 and Y. UBDA,Chem.Pharm.Bull. 22,390 (1974). 12 W. P. HAYSSand C. J. Tnaro~g SpectrocJ~imActa E3 24A, 323 (1968). [13] :9kiT~~ and D. W. BoYKIN,J. Org. Chem. 36,759
14 J. K. WILMSH~RST, J. Chem. Phys. 25,478 (1956). 1 H. H. Jmi, Chem.Rev. 53,191(1953). 2 H. W. THOMPSON, R. W. NEEDHAM and D. A. JAM~SON, 15 M. ST.C. FLETT,Trans. Faraday Sot. 44,767 (1948). Spectrochim.Acta 9,208 (1957) and K. V. RAMIAH, J. Mol. Spectrosc. I116 V. V. CHALAPATHI [3] H. W. THOMPSON and D. A. JAM@SON, SpectrocJh. M, 444 (lf=). Acta 13,236 (1958). 17j J. 0. HALPORD, J. Chem. Phys. 24,830 (1956). [4] N. FUS~N,M. L J~SIENand E. M. SHBLIDN, J. Am. E183 J. OVEREND and J. R. SCHERER,Specrrochim.Ada Chem.Sot. 76,2526 (1954). la, 773 (1960) [5] C. N. R. RAOand R. VENKATARAOHAVAN, Can. J. I’191 _ - R. C. LORD and F. A. MILLER, AI& . . Spectrosc. Chem. 39.1757 (1961). 10, 115 (1956). [6-j H. C. BROWNand Y. OKAMOTO, J. Am. Chem. Sot. [20] M. LIIER,Spectrochim.Ada 23A, 139 (1%7). 80,4979 (1958). [21] E. N. Pmm, J. Org. Gem. 42,1419 (1977).
El