Chlorobenzoic acids and derivatives: analysis of mixtures by thin-layer chromatography

ANALYSTANALYST Pub Date: DOI: 10.1039/AN9699400594

Abstract

Thin-layer chromatographic (silica gel G)RF values were obtained for the three isomeric monochlorobenzoic and two dichlorobenzoic acids. The p-bromophenacyl esters of benzoic, o-, m- and p-chlorobenzoic, and 3,4-dichlorobenzoic acids were prepared and RF values obtained. The esters of benzoic, m-chlorobenzoic and 3,4-dichlorobenzoic acids were separated from the ternary mixture by thin-layer chromatography. When 2,4-dinitrophenyl-hydrazine in hydrochloric acid solution reacted with the esters spotted at the origin, subsequent thin-layer chromatography gave characteristic two-spot patterns for each, and this facilitated recognition of the type of mixture of monochlorobenzoic acids. An explanation is given of the formation of two hydrazones from each ester.

Recommended Literature