ジアリールメタン類に関する研究(第1報)

1,2,4-トリメチルベンゼンとフォルムアルデヒドとの縮合反応

抄録

By the condensation of 1, 2, 4-trimethylbenzene (1, 2, 4-TMB) with formaldehyde bis (trimethylphenyl) methanes (BTMPM) are obtained. The condensation reaction in liquid phase was studied with various catalysts.
Results were summarized as follows.
1) p-Toluene sulfonic acid catalyst was more active than formic acid catalyst. But p-toluene sulfonic acid acted also as reactant, and formed a sulfonic acid ester. The molecular weight of condensate obtained by p-toluene sulfonic acid catalyst was somewhat higher than the molecular weight of BTMPM. On the other hand, formic acid catalyst didn't accompany such an undesirable side reaction, and the molecular weight of condensate corresponded to that of BTMPM. So formic acid was more suitable catalyst than p-toluene sulfonic acid. The optimum conditions using formic acid catalyst were; molar ratio (HCOOH: 1, 2, 4-TMB: HCHO)=6-8:4-6:1, reaction temp. 100°C, and reaction time 1-2hr. Results obtained under the above conditions were 95-100% conversion (based on formaldehyde used) and 95% selectivity.
2) Among solid catalysts studied phosphotungstic acid-silica gel, silicotungstic acid-silica gel and Amberlyst 15 were active for the condensation reaction.
3) Gas chromatogram of the condensate comprised mainly two isomeric fractions, and the ratio of these fractions didn't vary so much by reaction conditions.
4) The order of reactivity of C₉ aromatics with formaldehyde was 1, 3, 5-TMB»1, 2, 3-TMB>1, 2, 4-TMB»m-ethyltoluene (m-ET)>o-ET>p-ET. Therefore, for the production of high purity 1, 2, 4, 5-tetramethylbenzene the presence of 1, 3, 5-TMB and 1, 2, 3-TMB is unfavourable.