The cyclization kinetics of N-(2-methoxycarbonylphenyl)-N-methylsulfonamide to 1-methyl-(1H)-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide have been studied in glycinamide, morpholine, and butylamine buffers and in solutions of potassium hydroxide. The rate-limiting step consists in splitting off of the proton from the cyclic intermediate formed from the anion of the starting substrate. The value of the Bronsted coefficient β decreases with increasing pKa value of the conjugate acid of buffer. The calculated pKa value of the cyclic intermediate is 9.3.
对N-(2-甲氧羰基苯基)-N-甲基磺酰胺的环化动力学进行了研究,生成1-甲基-(1H)-2,1,3-苯并噻二嗪-4(3H)-酮-2,2-二氧化物。在甘氨酸、吗啉和丁胺缓冲液以及氢氧化钾溶液中研究了反应动力学。速率限制步骤在于从起始物质阴离子形成的环中间体中分离质子。Bronsted系数β的值随着缓冲液共轭酸的pKa值增加而减小。计算得到环中间体的pKa值为9.3。