Accession Number : AD0762102

Title :   Substituent Effects on the Acetyl Group Conformation and the Carbonyl Frequency in Acetophenones,

Corporate Author : CALGARY UNIV (ALBERTA) DEPT OF CHEMISTRY

Personal Author(s) : Krueger,P. J.

Report Date : 01 NOV 1972

Pagination or Media Count : 7

Abstract : The fundamental carbonyl stretching frequencies for o-, m-, and p-substituted acetophenones in dilute CCl4 solution are correlated with the electrophilic substituent constant sigma(+) by the expression v(C=O)(1/cm) = 11.53 sigma(+) + 1691.5(n=27, correlation coefficient = 0.988, standard deviation = 1.2/cm). The frequencies of carbonyl groups trans to an o-substituent follow this correlation, while those oriented cis to the substituent generally do not. Deviations from this correlation are interpreted in terms of dipole-dipole interactions, steric hindrance to planarity, intramolecular hydrogen bonding, and non-additivity of sigma(+) values for some combinations of substituents. The carbonyl frequenceis for singly m- and p-substituted acetophenones are also correlated with the polar and resonance components of sigma(+). Thus the sensitivity of the carbonyl frequency to the polar effect is greater than to the resonance effect. In mega-substituted acetophenones no precise correlation with polar substituent constants is observed. (Modified author abstract)

Descriptors :   (*ACETOPHENONES, MOLECULAR ENERGY LEVELS), KETONES, DIPOLE MOMENTS, MOLECULAR STRUCTURE, CANADA

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE