Magneto‐Chemical Studies on Some Aromatic Carbonyl Compounds

Abstract

AbstractA survey of the literature reveals that the magnetic data on the substituted aromatic aldehydes and ketones is very meagre and no systematic magneto‐chemical investigation appears to have been made on them. Therefore these aromatic carbonyl compounds form an interesting series for magneto‐chemical studies.These studies may throw some light on the effect of delocalisation of the electrons, the mesomerism of the carbonyl group, the positional isomerism and the interactions introduced by the substitution in the benzene ring.In the present studies the diamagnetic susceptibility of a number of the aromatic aldehydes and ketones has been measured with a sensitive Gouy balance. The magnetic susceptibilities of these compounds were calculated with the help of diamagnetic constants of atoms and multiple bonds as given in Ingold's book (1) also. A comparison between the experimentally determined and calculated χM values shows a poor agreement which may be attributed to the effects of the delocalisation of electrons, the mesomerism, the positional isomerism and the interactions of the substituent groups.In these compounds m‐isomer is comparatively more diamagnetic than ortho and para isomers although Bhatnagar and coworkers (2) have considered ortho isomer more diamagnetic than meta and para isomers, but in these aromatic carbonyl compounds m‐isomer may be regarded more diamagnetic on account of the electron with‐drawing‐nature of the carbonyl group. This is an analogous case to aryl β‐chlorovinylketones as studied by us (3).Yang's method (4) has been applied to evaluate the contribution towards molecular diamagnetism of the carbonyl group.