Gas Chromatography Analyses Of Relative Isomers In P-Chloro-benzoic Acid Prepared From Chlorotoluene By Catalyst Oxidation

As an important product of fine chemical, P -chlorobenzoic acid is widely used in the fields of organic intermidiates, pesticides, medicines, antiseptics, dyes and emitting materials. Therefore, it is important in scientificity and practicability to study the synthesis of P -chlorobenzoic acid and detection of its isomers.65 percent of transformation rate of P -chlorotoluene and 77.2 percent of yield of p-chlorobenzoic acid had been attained after about nine hours'reation under normal pressure at 140℃, on condition that original material was chlorotoluene mixtures, single phase catalyst was metal complexes of N-benzoyl-N-phenylhydroxylamine and oxidizer corned from air.The products, analyzed by gas chromatography, didn't contain o- or m-chlorobenzoic acid but p-chlorobenzoic acid whose purity was 87.7 percent. Meanwhile, the influences of different temperature, air velocity of flow and catalyst additives on catalytic oxidation had been studied.In order to study the process of single phase catalyst oxidation of chloro-toluenes mixtures to detect the oxidized product and its distribution, two approaches to detecting chlorotoluene isomers and chlorobenzoic acid isomers through gas chromatography have been respectively set up in our experiments.Mixtures of o-,m-,p-chlorotoluenes were separated in PEG-20M capillary column through direct sample. Satisfied results quantified by internal standard have been gained, that recovery was more than 94 percent, and RSD(relative standard deviation) less than 6 percent. Similarly, methylester derivations of o-,m,-p-chlorobenzoic acids were completely separated in HP-5 capillary column through the method of methylester derivation. The contents of chlorobenzoic acids isomers could been accurately quantified through internal standard, and the recovery was more than 92 percent, and RSD less than 3.6 percent.