Capillary gas chromatography of dihydroxybenzoic, -phenylacetic and -phenylpropionic acids

Abstract

All six possible ring-substittued dimethoxy and dihyroxy isomers of phynylacetic and β-phenylpropionic acids were prepared. The gas chromatographic (GC) separation, on an SE-54 coated fused-silica capillary column, of all 24 isomers (as their trimethylsilyl derivatives) is presented for the first time, as well as the first reported synthesis of 2,6-dihydroxyphenylacetic acid. The GC elution sequence of silylated dihydroxyphenylacetic and dihydroxyphenylpropionic acids is compaed to that of dihydroxybenzoic acids. Mass spectral (MS) fragmentation patterns of the silylated isomers reflect positions of the substituents and can be used to characterize isomers. The data presented wil allow the determination of these isomeric acids, based on their MS and GC data, relative to common, commercially available isomers. The developed data were applied to identifications of unknown phenolic acids of tobacco smoke.