The formation of a-methylated and a,a-dimethylated (di)acids during on-line (trans)methylation with tetramethylammonium hydroxide (TMAH) in a Curie-point pyrolysis unit is studied. The reaction of TMAH with nonanedioic, hexadecanedioic and octadecanoic acids is investigated to determine the contribution of the solvent system and the amount of TMAH added to this phenomenon. The results obtained clearly show a different behaviour of diacids in methanolic solutions compared to aqueous systems. At least three different reaction products were identified for the acids when using a methanolic solution of TMAH. Different relative amounts of by-products were formed when varying the amount of TMAH reagent relative to the normal methylated reaction product. A mechanism is postulated for their formation and a hypothesis is drawn up to explain the observed differences in reactivity for both solvents.
J. Anal. Appl. Pyrolysis

van den Berg, J. D. J., & Boon, J. J. (2001). Unwanted alkylation during direct methylation of fatty (di)acids using tetramethyl ammonium hydroxide reagent in a Curie-point pyrolysis unit. J. Anal. Appl. Pyrolysis, 61, 45–63. doi:10.1016/S0165-2370(01)00149-8