The rearrangement of 2-amino-1,3,4-thiadiazines to 3-amino-2-thiazolimines. Part 1. The rates of rearrangement of a series of 5-alkyl- and 5-aryl-2-amino-1,3,4-thiadiazines at 30 and 50 °C
作者:Reginald E. Busby、Terence W. Dominey
DOI:10.1039/p29800000890
日期:——
The rates of rearrangement of the series 5-methyl-, 5-ethyl-, 5-isopropyl-, and 5-t-butyl-2-amino-1,3,4-thiadiazines in strong acid have been followed by observing the u.v. absorptions of the protonated thiadiazine substrates or the product thiazolimines. The rates of rearrangement were found to be first order with respect to the thiadiazine concentration and the rates decreased along the series in
在强酸中观察了5-甲基-,5-乙基-,5-异丙基-和5-叔丁基-2-氨基-1,3,4-噻二嗪系列的重排速率,并观察了uv。质子化的噻二嗪底物或产物噻唑啉的吸收。发现重排的速率相对于噻二嗪浓度是一阶的,并且该速率以S N 2反应的特征沿着系列下降。2-氨基-1,3,4-噻二嗪与苯基,对硝基苯基和p的重排速率在5位的-羟基苯基基团都非常慢,而2-氨基-5-苄基-1,3,4-噻二嗪的重排比这些芳基噻二嗪快得多,但比5-甲基和5-乙基化合物慢得多。在4.47–8.12 M -HCl范围内的各种酸强度下,遵循2-氨基-5-甲基-1,3,4-噻二嗪的重排速率。反应最终达到平衡,并且测得的常数k 1等于正向和反向反应的速度常数(k r + k –r)之和。既ķ ř和ķ -r被认为是类似地依赖于酸度和水分活度。使用HLong和Paul用取代的苯胺得到0个值,发现对数10 k 1对– H 0的图是线性的,斜率等于0