作者:František Tureček、Shetty Vivekananda、Martin Sadílek、Miroslav Polášek
DOI:10.1021/ja0202457
日期:2002.11.1
the lactone enols are 15-20 orders of magnitude more acidic than the corresponding lactones, with enol pK(a) values increasing from 5.6 (C(4)-1) to 14.5 (C(6)-1). Lactone enols are moderately weak bases in water with pK(BH) in the range of 3.9-8.1, whereas the lactones are extremely weak bases of pK(BH) in the range of -10.5 to -17.4. The acid-base properties of lactone enols point to their high reactivity
2-Hydroxyoxol-2-ene (C(5)-1),γ-丁内酯的烯醇互变异构体,是在气相中产生的,是迄今为止难以捉摸的内酯烯醇类的第一个代表,并通过中和-再电离质谱法显示作为一个孤立的物种非常稳定。QCISD(T)/6-311+G(3df,2p) 从头算计算提供了气态内酯烯醇的形成焓、质子亲和力和气相碱度,具有四- (C(4)-1)、五- (C(5)-1) 和六元环 (C(6)-1)。C(4)-C(6) 内酯和烯醇以及参考羧酸烯醇 CH(2)=C(OH)(2) (3) 和 CH(2)=C(OH)OCH( 3) (4) 也在水溶液中计算。C(4)-C(6) 内酯烯醇的气相质子亲和力范围为 933-944 kJ mol(-)(1),酸度范围为 1401-1458 kJ mol(-)(1) . 在水溶液中,内酯烯醇的酸性比相应的内酯高 15-20 个数量级,烯醇 pK(a) 值从 5.6 (C(4)-1)