顺1,4-聚丁二烯在不同溶剂中的环化反应及其机理的研究

STUDY ON THE CYCLIZATION OF CIS-1,4 POLYBUTADIENE IN VARIOUS SOLVENTS AND ITS MECHANISM

以烯丙基氯 一氯二乙基铝 (CH2 CHCH2 Cl AlEt2 Cl)催化体系研究了顺 1 ,4 聚丁二烯在不同溶剂(三甲苯、二甲苯、甲苯、苯和环己烷 )中的环化反应 .结合环化产物红外光谱的测定 ,提出芳烃溶剂分子经受阳碳离子亲电取代作用而参与环化的机理 ,以此解释了若干实验事实 ,并对已有文献报道进行了讨论 .

The cyclization of cis 1,4 polybutadiene in various solvents (mesitylene,xylene,toluene,benzene and cyclohexane) with the catalyst composed of CH\-2 CHCH\-2Cl\|AlEt\-2Cl was studied.The infrared spectra of the cyclized products were investigated.It was shown that the products produced in cyclohexane and mesitylene have infrared spectra identical with those of the original cis 1,4 polybutadiene and the products obtained in other aromatics have infrared spectra different from each other and distinguishing with those of the parent cis 1,4 polybutadiene.The analyses of infrared spectra came to the conclusion that the molecules of aromatic solvent participate in cyclization of cis 1,4 polybutadiene at the given condition.A possible reaction scheme involving an electrophilic substitution of carbonium ions for Ar—H of aromatic solvents was proposed.Some experimental facts were explained with great satisfaction on the basis of the above mechanism.