两相催化体系中双子表面活性剂对1-十二烯氢甲酰化反应的促进作用

报道了水溶性铑膦配合物组成的复合催化体系催化1-十二烯氢甲酰化反应中,双子表面活性剂[二溴化-(N,N,N′,N′-四甲基)-N,N′-二(十六烷基)-乙二铵]形成胶束的助催化作用.结果表明,在水/有机两相中,双子表面活性剂比单链表面活性剂CTAB具有更好加速催化反应的作用,并使烯烃氢甲酰化的区域选择性显著提高.这归因于双子表面活性剂有较低的cmc,可形成更加紧密规整的胶束结构,有利于增溶在胶束中的烯烃与铑催化剂配位和生成正构醛.

Hydroformylation of 1-Dodecene Catalyzed by Water Soluble Rhodium-Phos-phine Complexes in Micellar System with Cationic Gemini Surfactant

The promotion of 1,2-bis(dimethylcetyl ammonium bromide) ethane[G(Et)] cationic gemini surfactant for the hydroformylation of 1-dodecene in the oil/water biphasic catalytic system is reported. The critical micelle concentration(cmc) and solubilization of laurylbenzene in G(Et) solution were determined. The cmc of G(Et) was 3.8×10-5 mol/L, which was much lower than that 9.6×10-4 mol/L of CTAB. The influences of the concentration of G(Et) and the stirring rate on 1-dodecene hydroformylation were studied. The results show that in the biphasic system containing the catalyst RhCl(CO)(TPPTS)2 and TPPTS[TPPTS=tris(sodium-m-sulfonatophenyl) phosphine], the hydroformylation of 1-dodecene in the presence of gemini surfactant G(Et) occured with a higher turn over frequency(TOF=1 066 h-1 ) and higher selectivity for normal aldehyde[n(normal)/n(iso)=5.7] than that using conventional monomeric surfactant CTAB[TOF=901 h-1 , n(normal)/n(iso)=3.7]. The phenomena could be attributed to that G(Et) has a lower cmc and could form more compact and spherocylindrical micelle in the solution. The lower cmc and good surface tension reduction ability of G(Et) would be favorable for decreasing phase transfer energy barrier of 1-dodecene from the core of micelle to the interface of two phases where 1-dodecene coordinated with rhodium catalysts, and thereby the reaction rates was accelerated greatly. The more compact structure of the spherocylindrical micelle of G(Et) would be favorable for the formation of linear aldehyde.