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Infrared spectroscopic studies of substituted 1,2-diphenylcyclopropenes
Spectrochimica Acta, Vol. 45A, No. 6, pp. 695496, Printed in Great Britain.
1989. 0
058+8539/89 $3.00+0.00 1989 Pergamon Press plc
SHORT COMMUNICATION Infrared spectroscopic studies of substituted 1,2-diphenylcyclopropenes I. A. BOYARSKAYA, I. N. DOMNIN and S. KH. AKOPYAN Institute of Chemistry, Leningrad University, 199034, Leningrad, U.S.S.R. (Receioed 12 July 1988; infinaljbrm
10 October 1988;accepted 22 November 1988)
Abstract-For the investigation of the character of a substituent at position 3 of the ring and the double bond, i.r. spectra of substituted 1,2-diphenilcyclopropenes were studied. Frequencies and integral intensities of the double bond stretching vibration band were determined. It was proved that changes of the band’s parameters caused by intermolecular interactions are substantially smaller than effects observed by changing the substituent. On the basis of correlation between changes of intensities of the vc,c band and resonance constants of substituents and the character of the frequency dependence, a conclusion was reached on the resonance interactions of the substituent with u~,,,~ - MO of the cycle.
INTRODUCTION It is known that i.r. band intensities are often more sensitive to electronic changes in molecules than frequencies, and can be used for estimation of intramolecular interactions [l]. In the present work the peculiarities of intramolecular interactions of 1,2diphenyl-3-substituted cyclopropenes were studied by i.r. spectrdscopic analysis. EXPERIMENTAL The synthesis of 1,2-diphenyl-3-styrylcyclopropene [Z], 1,2-diphenylcyclopropene [3], 1,2,3-triphenylcyclopropene [4], 1,2-diphenylcyclopropene-3-carboxylic acid [S] and derivatives of this acid: methyl ester [6], chloranhydride and nitril [7], 3-hydroxymethyl [S] was carried out by known procedures. Infrared spectra of dilute solutions of the above-mentioned compounds were recorded on an IR-75 spectrophotometer (Carl Zeiss, Jena), with a scanning rate-of 3-5 cn-‘/min, and a split spectral width of 2.5cm-‘. The concentration of the solutions were O.O5XL20mol/l. For the Y- band intensity determination, the method of graphic separation was used. Integration was carried out over three half-widths of the band absorbtion maximum. The intensity determination error is lO-20%. RESULTS AND
penes are given. As the effect of the substituent was investigated by i.r. solution spectra it was necessary to estimate the influence of intermolecular interactions on the parameters of the i.r. bands. For this purpose we have measured i.r. spectra of all [he studied cyclopropenes in two solvents; besides which, for l,Zdiphenylcyclopropene the V~ band parameters were determined in a series of different solvents (see Table 2). It is evident from the data of Table 1 that a.substantial decrease ,45:6-P
A=
=
2.8-6.la&
n=7, r=0.984, So = 0.17
for solutions in CHCl,: A’.’ c==c=
29-66 . . ui, n=7, r=O.965, S,-,=O.21.
Calculations were carried out by the least-squares method. The relative error in the correlation parameter determination is less than 30%, which corresponds to the intensity error determination in the case of a strong overlapping of absorption bands. Thus, the resonance interactions have a predominant influence
DISCUSSION
In Table 1 average frequencies and intensities (taken from several independent measurements) for the v= absorption band in a row of 1,2-diphenylcyclopro-
SAfA)
(about nine-fold) in intensity takes place on the exchange of donor substituehts for acceptor ones. This effect is much more distinct than that caused by the influence of intermolecular interactions. The changes in frequencies of the vW band due to the effect of substituents are of the order of 10 times greater than those observed on transition from polar solvents to non-polar ones. The data obtained were used for establishing a correlation between values of A% and the reactive parameters of the substituents. The correlation found between AZ and resonance constants ui for solutions in Ccl, was:
Table 1. Frequencies (v. cm-‘) and absolute intensities (A, lo-scm’/molec. s) of the double bond band in 3-substituted 1,2-diphenylcyclopropenes “mm
ccl, 1 2 3 4 5 6 7 8 9 695
CH=CH-Ph Ph CH,OH H CN CONMe, CO,Me CO,H COCl
1821 1822 1816 1821 1845 1844 1850 1855
CHCl, 1823 1821 1847 1844 1852 1855 1855
A
Ccl, 14.3 11.5 9.4 7.0 3.3 5.2 3.8 1.6
CHCl, 12.8 8.2 4.0 5.1 3.6 4.0 1.7
I. A. BOYARSKAYA et al.
696 Table 2. Frequencies (v, cm-‘)
on
and intensities (A, 10-8cm2/molec. cyclopropene
Solvent
Pentane
Cyclohexane
vc=G”.. A,
1825 5.6
1824 5.6
s) of the double bond band in 1,2-diphenyl-
ccl,
CHCI,
CH,CI,
CH,CN
CHBr,
1821 7.0
1821 8.2
1821 8.4
1820 6.6
1819 8.2
the intensity of double bond bands in 3-substituted 1,2-diphenylcyclopropenes. From the results of the vibrational problem solution for the unsubstituted cyclopropene molecule [9], it follows that the so-called stretching vibration of the double bond has a complex form. Single bonds in the ring make a substantial contribution to it. However, calculations of the vibration forms carried out with the aid of a programme [lo] for 3-hydroxymethyl cyclopropene and cyclopropene-3-carboxylic acid, shows that the vibrational form changes weakly on transition from the unsubstituted cyclopropene to its derivatives. It allows us to suppose that in a chosen series of 1,2-diphenyl-3-substituted cyclopropenes, the changes in the form of this vibration will be small. Therefore the decrease in the absolute value of (+@Q),, with an increasing acceptor force of substituent can be connected with a change of electro-optical parameters, probably with a change of (&&Yq&,-, value. This is connected with an electron density decrease in the regiqn of the double bond, caused by the influence of the substituent. Additional information about the mechanism of substituent interaction with the cycle can be obtained by analysis of substituent influence on the frequency of the double bond. With increasing acceptor power of the substituent, a bathochromic shift of the v= vibration is observed (see Table 1). In other words, the force
constant of the double bond is increasing, and electron density in the region of this bond is decreasing. One can assume from this fact that the substituent interacts with the awn,,,,-orbital of the cycle, which is antibonding towards the double bond. REFERENCES
CII A. R. KATRITZKYand R. D. TOPSON,Chem. Rev. 11,639 (1977).
I. B. L~GOSHand I. N. D~MNIN, PI M. I. KOMENDANTOV, J. org. Chem. U.S.S.R., EngI. Transl. 21, 933 (1985). c31 Z.-ICHI YOSHIDAand H. MIYAHARA,Chem. Lett. 335, (1972). II41 R. BRESLOWand P. DOWD, .I. Am. them. Sot. l&,2729 (1963). J. gen. CSI I. A. DYAKONOVand M. I. KOMENDANTOV,
Chem. U.S.S.R., Engl. Transl. 33, 2387 (1963).
M. I. KOMENDANTOV, I. N. DOMNIN,R. N. KENBAEVA and T. N. GRIGOROVA,J. org. Chem. U.S.S.R. 9, 1420 (1973). c71 E. H. WHITE, R. E. K. WINTER, R. GRAEVE, U. ZIRNGIBL,E. W. FRIEND, H. MASKILL,U. MENDE, G. KREILING, H. P. REISENAUERand G. MAIER, Chem. Ber. 114, 3906 (1981). 181 R. BRESLOW,J. LOCKHARTand A. SMALL J. Am. them. Sot. 84, 2793 (1962). c91 K. B. WIBERG, R. C. DEMPSEYand J. J. WENDOLOSKI, J. phys. Chem. 88, 5596 (1984). WI L. A. GRIBOV and V. A. DEMENTJEV, Methods and WI
Algorithms of Calculations in the Theory of Vibrational Spectra of Molecules. Nauka, Moscow (1981).
1989. 0
058+8539/89 $3.00+0.00 1989 Pergamon Press plc
SHORT COMMUNICATION Infrared spectroscopic studies of substituted 1,2-diphenylcyclopropenes I. A. BOYARSKAYA, I. N. DOMNIN and S. KH. AKOPYAN Institute of Chemistry, Leningrad University, 199034, Leningrad, U.S.S.R. (Receioed 12 July 1988; infinaljbrm
10 October 1988;accepted 22 November 1988)
Abstract-For the investigation of the character of a substituent at position 3 of the ring and the double bond, i.r. spectra of substituted 1,2-diphenilcyclopropenes were studied. Frequencies and integral intensities of the double bond stretching vibration band were determined. It was proved that changes of the band’s parameters caused by intermolecular interactions are substantially smaller than effects observed by changing the substituent. On the basis of correlation between changes of intensities of the vc,c band and resonance constants of substituents and the character of the frequency dependence, a conclusion was reached on the resonance interactions of the substituent with u~,,,~ - MO of the cycle.
INTRODUCTION It is known that i.r. band intensities are often more sensitive to electronic changes in molecules than frequencies, and can be used for estimation of intramolecular interactions [l]. In the present work the peculiarities of intramolecular interactions of 1,2diphenyl-3-substituted cyclopropenes were studied by i.r. spectrdscopic analysis. EXPERIMENTAL The synthesis of 1,2-diphenyl-3-styrylcyclopropene [Z], 1,2-diphenylcyclopropene [3], 1,2,3-triphenylcyclopropene [4], 1,2-diphenylcyclopropene-3-carboxylic acid [S] and derivatives of this acid: methyl ester [6], chloranhydride and nitril [7], 3-hydroxymethyl [S] was carried out by known procedures. Infrared spectra of dilute solutions of the above-mentioned compounds were recorded on an IR-75 spectrophotometer (Carl Zeiss, Jena), with a scanning rate-of 3-5 cn-‘/min, and a split spectral width of 2.5cm-‘. The concentration of the solutions were O.O5XL20mol/l. For the Y- band intensity determination, the method of graphic separation was used. Integration was carried out over three half-widths of the band absorbtion maximum. The intensity determination error is lO-20%. RESULTS AND
penes are given. As the effect of the substituent was investigated by i.r. solution spectra it was necessary to estimate the influence of intermolecular interactions on the parameters of the i.r. bands. For this purpose we have measured i.r. spectra of all [he studied cyclopropenes in two solvents; besides which, for l,Zdiphenylcyclopropene the V~ band parameters were determined in a series of different solvents (see Table 2). It is evident from the data of Table 1 that a.substantial decrease ,45:6-P
A=
=
2.8-6.la&
n=7, r=0.984, So = 0.17
for solutions in CHCl,: A’.’ c==c=
29-66 . . ui, n=7, r=O.965, S,-,=O.21.
Calculations were carried out by the least-squares method. The relative error in the correlation parameter determination is less than 30%, which corresponds to the intensity error determination in the case of a strong overlapping of absorption bands. Thus, the resonance interactions have a predominant influence
DISCUSSION
In Table 1 average frequencies and intensities (taken from several independent measurements) for the v= absorption band in a row of 1,2-diphenylcyclopro-
SAfA)
(about nine-fold) in intensity takes place on the exchange of donor substituehts for acceptor ones. This effect is much more distinct than that caused by the influence of intermolecular interactions. The changes in frequencies of the vW band due to the effect of substituents are of the order of 10 times greater than those observed on transition from polar solvents to non-polar ones. The data obtained were used for establishing a correlation between values of A% and the reactive parameters of the substituents. The correlation found between AZ and resonance constants ui for solutions in Ccl, was:
Table 1. Frequencies (v. cm-‘) and absolute intensities (A, lo-scm’/molec. s) of the double bond band in 3-substituted 1,2-diphenylcyclopropenes “mm
ccl, 1 2 3 4 5 6 7 8 9 695
CH=CH-Ph Ph CH,OH H CN CONMe, CO,Me CO,H COCl
1821 1822 1816 1821 1845 1844 1850 1855
CHCl, 1823 1821 1847 1844 1852 1855 1855
A
Ccl, 14.3 11.5 9.4 7.0 3.3 5.2 3.8 1.6
CHCl, 12.8 8.2 4.0 5.1 3.6 4.0 1.7
I. A. BOYARSKAYA et al.
696 Table 2. Frequencies (v, cm-‘)
on
and intensities (A, 10-8cm2/molec. cyclopropene
Solvent
Pentane
Cyclohexane
vc=G”.. A,
1825 5.6
1824 5.6
s) of the double bond band in 1,2-diphenyl-
ccl,
CHCI,
CH,CI,
CH,CN
CHBr,
1821 7.0
1821 8.2
1821 8.4
1820 6.6
1819 8.2
the intensity of double bond bands in 3-substituted 1,2-diphenylcyclopropenes. From the results of the vibrational problem solution for the unsubstituted cyclopropene molecule [9], it follows that the so-called stretching vibration of the double bond has a complex form. Single bonds in the ring make a substantial contribution to it. However, calculations of the vibration forms carried out with the aid of a programme [lo] for 3-hydroxymethyl cyclopropene and cyclopropene-3-carboxylic acid, shows that the vibrational form changes weakly on transition from the unsubstituted cyclopropene to its derivatives. It allows us to suppose that in a chosen series of 1,2-diphenyl-3-substituted cyclopropenes, the changes in the form of this vibration will be small. Therefore the decrease in the absolute value of (+@Q),, with an increasing acceptor force of substituent can be connected with a change of electro-optical parameters, probably with a change of (&&Yq&,-, value. This is connected with an electron density decrease in the regiqn of the double bond, caused by the influence of the substituent. Additional information about the mechanism of substituent interaction with the cycle can be obtained by analysis of substituent influence on the frequency of the double bond. With increasing acceptor power of the substituent, a bathochromic shift of the v= vibration is observed (see Table 1). In other words, the force
constant of the double bond is increasing, and electron density in the region of this bond is decreasing. One can assume from this fact that the substituent interacts with the awn,,,,-orbital of the cycle, which is antibonding towards the double bond. REFERENCES
CII A. R. KATRITZKYand R. D. TOPSON,Chem. Rev. 11,639 (1977).
I. B. L~GOSHand I. N. D~MNIN, PI M. I. KOMENDANTOV, J. org. Chem. U.S.S.R., EngI. Transl. 21, 933 (1985). c31 Z.-ICHI YOSHIDAand H. MIYAHARA,Chem. Lett. 335, (1972). II41 R. BRESLOWand P. DOWD, .I. Am. them. Sot. l&,2729 (1963). J. gen. CSI I. A. DYAKONOVand M. I. KOMENDANTOV,
Chem. U.S.S.R., Engl. Transl. 33, 2387 (1963).
M. I. KOMENDANTOV, I. N. DOMNIN,R. N. KENBAEVA and T. N. GRIGOROVA,J. org. Chem. U.S.S.R. 9, 1420 (1973). c71 E. H. WHITE, R. E. K. WINTER, R. GRAEVE, U. ZIRNGIBL,E. W. FRIEND, H. MASKILL,U. MENDE, G. KREILING, H. P. REISENAUERand G. MAIER, Chem. Ber. 114, 3906 (1981). 181 R. BRESLOW,J. LOCKHARTand A. SMALL J. Am. them. Sot. 84, 2793 (1962). c91 K. B. WIBERG, R. C. DEMPSEYand J. J. WENDOLOSKI, J. phys. Chem. 88, 5596 (1984). WI L. A. GRIBOV and V. A. DEMENTJEV, Methods and WI
Algorithms of Calculations in the Theory of Vibrational Spectra of Molecules. Nauka, Moscow (1981).