异丁烯-对甲基苯乙烯无规共聚物可见光溴化反应的选择性

Photobromination selectivities of isobutylene-p-methyl styrene random copolymer irradiated with visible light

使用气相色谱仪对几种不同纯度的正己烷和环己烷进行了组分分析,并对包括2-甲基戊烷、3-甲基戊烷和甲基环戊烷在内的正己烷的主要支链型同分异构体成分,以及异丁烯-对甲基苯乙烯无规共聚物中对甲基苯乙烯结构单元的模型分子对二甲苯和对二异丙苯在波长为365~840 nm的可见光照射下的光溴化反应进行了对比,筛选出可以有效避免溶剂发生光溴化副反应并提高目标光溴化反应选择性的可见光波长。此外,将异丁烯-对甲基苯乙烯无规共聚物在质量分数为85.7400%~99.9600%的溶剂正己烷和环己烷中的光溴化反应的选择性进行了对比,并考察了除酸剂碳酸氢钠和反应温度对异丁烯-对甲基苯乙烯无规共聚物在正己烷中光溴化反应的影响。结果表明,波长为595 nm和630 nm的可见光可作为异丁烯-对甲基苯乙烯无规共聚物光溴化反应的光源,在质量分数为85%的工业正己烷中即可实现良好的光溴化反应,溴的有效利用率可达到70%~80%;碳酸氢钠作为酸蚀剂可以有效抑制异丁烯-对甲基苯乙烯无规共聚物的凝胶化反应。此外,反应温度对光溴化反应有一定影响,当反应温度从5℃降至-20℃时,溴化反应速率降低了58.87%。

Several types of n-hexane and cyclohexane with different purities were analyzed by gas chromatograph, and the photobromination reactions of the major branched isomer compositions of n-he-xane including 2-methylpentane, 3-methylpentane and methylcyclopentane, and model molecules of structural unit of p-methyl styrene in isobutylene-p-methyl styrene random copolymer, p-xylene and 1,4-diisopropylbenzene, were compared with visible light with the wavelengths of 595 nm and 630 nm as light sources. The visible light wavelengths with which photobromination side reaction of the solvent could be effectively avoided, and with which the selectivity of target photobromination reaction was improved were screened. In addition, the selectivities of photobromination reaction of isobutylene-p-methyl styrene random copolymer in the solvent of n-hexane and cyclohexane with the purities between 85.740 0% and99.960 0% were compared, and the effect of sodium bicarbonate as the acid etching agent and reaction temperature on the photobromination reaction of isobutylene-p-methyl styrene random copolymers in n-hexane were investigated. The results showed that visible light with the wavelengths of 595 nm and630 nm could be used as the light sources for the photobromination reaction of isobutylene-p-methyl styrene random copolymer, and efficient photobromination reaction could be achieved in industrial grade n-hexane whose purity was 85% with effective avai-lability of bromine of 70%-80%. The gelation reaction of isobutylene-p-methyl styrene random copolymer could be effectively inhibited with sodium bicarbonate as the acid etching agent. Moreover, to a certain extent, the reaction temperature had an effect on the photobromination reaction, and there was a decrease of 58.87% in the bromination rate when the reaction temperature decreased from 5 ℃ to-20 ℃.