Methylation of linear alkylbenzenesulfonate with diazomethane

• Published in: BUNSEKI KAGAKU Vol. 38; no. 3; pp. 143 - 145
• Main Authors: SHINOHARA, Ryota, TERASHI, Akiko, HANADA, Yoshifumi
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society for Analytical Chemistry 05.03.1989
• Subjects: gas chromatographic determination of LAS; LAS-amine complexes; methyl derivative of linear alkylbenzene sulfonates(LAS)
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.38.3_143

Methylation with diazomethane was considered to be unavailable for alkylbenzenesulfonate (LAS) in environmental samples because of the difficulty of extracting them into organic solvent as their sulfonic acids. Therefore LAS methyl esters have been obtained by reacting with phosphorus pentachloride and then methanol. In this study, we examined if diazomethane could directly methylate LAS-amine complexes known to be extracted into an organic solvent. Since primary and secondary amines might react with diazomethane, we tested some kinds of tertiary amines. Triethylamine, tripropylamine and tributylamine provided good results. The procedure was as follows. An appropriate amount of LAS and 100 ml of water were out into a separatory funnel. Buffer solution (pH 6.8) and 0.1 ml of amine were added to it and mixed well. After extracting with dichloromethane, the organic layer was separated and concentrated almost to dryness and 1 ml of diazomethane/ether solution was added to the residue. The measurement was performed by a gas chromatograph equipped with a flame ionization detector. We got the same gas chromatogram pattern as that obtained with the phosphorus pentachloride method. The recovery was 89114% compared with the previous method. The methylation products were confirmed to be LAS methyl esters by their mass spectra.