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在苯、乙醚等溶剂中,CF_2Br_2与 PhSNa不反应或反应极慢.加入催化量的二苯并-18-冠-6,则反应在数分钟内完成,主产物 PhSCF_2Br 的产率提高至75～85%,副产物 PhSCF_2H 及 PhSSPh受到显著抑制.本体系明显优于最近文献报道的其他反应体系.讨论了反应机理,给出了表明反应主要是阴离子型链式机理的进一步证据:反应速度和产物分布对水、醇等给质子性杂质敏感,对氢原子供体型溶剂及光、氧、自由基捕获剂不敏感;在以 CCl_4为溶剂的反应中,得到 PhSCF_2Cl 和属于~-CCl_3的产物,而未检测到自由基型机理所预期的 CCl_3CCl_3.
The reaction between CF_2Br_2 and PhSNa did not react with PhSNa or very slowly in solvents such as benzene and diethyl ether.The reaction was completed in a few minutes with the addition of dibenzo-18-crown-6 in a catalytic amount, and the yield of the main product PhSCF_2Br was increased to 75 ~ 85%, PhSCF_2H and PhSSPh byproducts were significantly inhibited.The system was significantly better than other reaction systems recently reported in the literature.The reaction mechanism was discussed and further evidence was given indicating that the reaction is mainly an anionic chain mechanism: the reaction rate and product The distribution is sensitive to proton impurities such as water and alcohol, and is not sensitive to hydrogen atom donor solvents and light, oxygen and free radical trapping agents. In reaction with CCl_4 as solvent, PhSCF_2Cl and products belonging to ~ -CCl_3 are obtained, while CCl_3CCl_3 expected from the free radical mechanism was not detected.