Absolute rates of bromination were measured for two series of derivatives of steroidal ketones 3, enolacetates 1 and enol methyl ether 2. Axial substituents exhibited a large effect on rates, which increased by 15,000 fold on going from (X=CH3; Y=CN) to (X=Y=H). From the bromide ion effect it was concluded that the first step (formation of an intermediate bromonium ion) was reversible and that the
测量了甾族酮3的两个系列衍生物,烯醇乙酸酯1和烯醇甲基醚2的溴化绝对速率。轴向取代基对速率表现出很大的影响,从(X = CH 3; Y = CN)变为(X = Y = H)时,轴向取代基增加了15,000倍。从溴离子效应可以得出结论,第一步(中间体溴离子的形成)是可逆的,并且第二步(卤代酮4或5或卤代缩醛8或9的形成)与第一步相比较慢。推断该中间体是高度不对称的溴离子,而不是纯的氧碳鎓离子。
Jacquesy,J.-C.; Levisalles,J., Bulletin de la Societe Chimique de France, 1962, p. 1866 - 1874