Accession Number:

AD0762102

Title:

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

Descriptive Note:

Corporate Author:

CALGARY UNIV (ALBERTA) DEPT OF CHEMISTRY

Personal Author(s):

Report Date:

1972-11-01

Pagination or Media Count:

7.0

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 vCO1cm 11.53 sigma 1691.5n27, correlation coefficient 0.988, standard deviation 1.2cm. 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

Subject Categories:

  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE