High-performance liquid chromatographic separation of the intermediate products in the synthesis of trimethylolpropane

Abstract

Industrial synthesis of trimethylolpropane (TMP) can be carried out by condensation of n-butyraldehyde with formaldehyde followed by catalytic hydrogenation of the reaction products_ During the synthesis it is important to be able to control the composition of the condensation mixture before hydrogenation by a fast analytical method. Since most of the components are quite unstable and of low volatility, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) seemed to be the most suitable methods for this purpose, and here we report the method we worked out. For a preliminary TLC analysis, silica gel or RP-8 bonded silica gel plates were used. For separation of the intermediates in the TMP synthesis by HPLC three different columns were employed: LiChrosorb RP-2 (10 ,mr; Merck); RP-8 (10 pm; Perkin-Elmer); and PBondapak CN (Waters). In all cases, mixtures of the following solvents were used as the mobile phase: water, tetrahydrofuran (THF), acetonitrile and methanol. The best results were obtained on LiChrosorb RP-2 by elution with water-methanol. In order to confirm the structure of the components, preparative HPLC was carried out on a preparative Lobar RP-8 (Merck) column by elution with watermethanol.