Magnetic susceptibilities of organic compounds: Part V-Influence of substituents on diamagnetic susceptibilities of disubstituted and trisubstituted benzenes

Abstract

The magnetic susceptibilities of a number of triads 6f isomeric disubstituted benzenes have been determined, choosing the compounds in such a way that the substituents are present in the following combinations: (i) two electron-releasing substituents, (ii) a halogeno and an electron-releasing substituent, (iii) a halogeno and an electron-attracting substituent, and (iv) two halogeno substituents. The data show that for types (i), (ii) and (iv), the <em>ortho </em>isomers have the highest magnetic susceptibilities, the susceptibilities decreasing in the order: <em>ortho > meta > para</em>; for type (iii), the <em>meta-isomers </em>have the highest susceptibilities, the susceptibilities decreasing in the order: <em>meta > para > ortho. </em>The diamagnetic susceptibilities of some isomeric trisubstituted benzenes have also been determined and the data reveal that the susceptibility is the highest where the crowding of substituents is the highest (1,2,3-isomer) and lowest where the substituents are staggered and least crowded (1,3,5-isomer). Another observation made in the case of trisubstituted benzene is the applicability of a principle of additivity of their diamagnetic susceptibilities.