PEG1000强化钾盐催化硫醇β-羟乙基化反应

PEG1000 enhanced potassium salt catalyzed β-hydroxyethylation of mercaptan

摘要:

在常压、无溶剂条件下，以聚乙二醇（PEG）为相转移剂，钾盐为催化剂，碳酸乙烯酯（EC）和硫醇（RSH）为原料合成β-羟乙基烷基硫醚（RSCH2CH2OH）。系统考察PEG对不同钾盐在RSH的β-羟乙基化反应中的固/液相转移作用以及EC用量对RSCH2CH2OH选择性的影响。通过GC和GC-MS对RSH转化率、RSCH2CH2OH选择性和副产物进行分析。结果表明，PEG本身没有催化活性，与单独加入0.5%（以RSH物质的量为基准，下同）K2CO3相比，同时加入1.0%PEG和0.5%K2CO3可显著提高RSH转化率和反应速率。PEG相对分子质量<1000时，PEG对K2CO3催化活性的强化作用随着PEG链长度的增长而增强。RSCH2CH2OH的选择性随着EC/RSH物质的量的比值的增大（≥1.02）而降低，副产物为乙烯基烷基硫醚和乙二醇。无溶剂条件下，PEG的加入能有效打破钾盐催化剂与液相反应物之间的相界面限制，增强钾盐催化活性，缩短反应时间，提高产品收率。

Abstract:

The β-hydroxyethyl alkyl sulfide (RSCH2CH2OH) was synthesized by using polyethylene glycol (PEG) as phase transfer agent, potassium salt as catalyst, ethylene carbonate (EC) and mercaptan (RSH) as raw materials under atmospheric pressure and solvent-free. The transfer effect of PEG on the solid/liquid phases of different potassium salts in the β-hydroxyethylation of RSH and the effect of the amount of EC on the selectivity of RSCH2CH2OH have been investigated. The conversion of RSH, selectivity of RSCH2CH2OH and by-products were analyzed by GC and GC-MS. The results show that PEG alone has no catalytic activity. Compared with adding 0.5% (based on the molar amount of RSH, the same below) K2CO3 alone, the reaction rate and conversion rate of RSH have been significantly improved by adding 1.0%PEG and 0.5%K2CO3. The enhancement effect of PEG on the catalytic activity of K2CO3 increases with the increase of the length of PEG chain when the relative molecular weight of PEG is less than 1000. The selectivity of RSCH2CH2OH decreases as the ratio of the molar ratio of EC/RSH increases (≥1.02), the byproducts are vinyl alkyl sulfide and ethylene glycol. The addition of PEG can effectively break the phase interface limitation between the potassium salt catalyst and the liquid phase reactant, enhance the potassium salt catalytic activity. Besides, it can shorten the reaction time and increase the product yield under the solvent-free conditions.