CATALYTIC REACTIONS INVOLVING AZOMETHINES .7. RATES AND EQUILIBRIA OF ALDIMINE FORMATION WITH 3-HYDROXYPYRIDINE-4-ALDEHYDE AND ALANINE
CATALYTIC REACTIONS INVOLVING AZOMETHINES .7. RATES AND EQUILIBRIA OF ALDIMINE FORMATION WITH 3-HYDROXYPYRIDINE-4-ALDEHYDE AND ALANINE
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DOI：
10.1021/ja00985a020
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发表时间：
1967-01-01
影响因子：
15
通讯作者：
BRUICE, TC
中科院分区：
文献类型：
--
作者：
AULD, DS;BRUICE, TC
本文报道了3-羟基吡啶-4-醛与DL-丙氨酸反应生成乙二胺和水解反应的pH速率和平衡曲线(30，µ=1.0，Kc1)。DL-丙氨酸和3-羟基吡啶-4-醛通过DL-丙氨酸作为不带电胺(A)对醛的阳离子形式(PCHO+)、两性离子形式(PCHO-)和阴离子形式(PCHO-)进行限速攻击而生成乙二胺(见图I)。3-羟基吡啶-4-醛的醇胺中间体的脱水速率远大于吡啶-4-醛的脱水速率，表明邻羟基参与了分子内催化剂的作用。根据测定的乙二胺生成在pH 4.0-12.2范围内随pH变化的平衡常数(ATpH)和DL-丙氨酸(Kah“Rah)、3-羟基吡啶-4-ALDE-Hyde(‘+，R’pcho)及其产物乙二胺(Rs，Rs+，Ran+)的酸离解常数，计算了乙二胺生成的各种平衡常数(R，Ru7G)(见图II)。通过比较DL-丙氨酸+3-羟基吡啶-4-醛和DL-丙氨酸+吡啶-4-醛的平衡常数曲线，证明了在中性和弱酸性pH范围内，取代吡啶-4-醛3位羟基可提高乙二胺的浓度。
This paper reports the pH-rate and equilibrium profiles (30, µ= 1.0 with KC1) for aldimine forma-tion and hydrolysis in the reaction of 3-hydroxypyridine-4-aldehyde with DL-alanine. Aldimine formation from DL-alanine and 3-hydroxypyridine-4-aldehyde proceeds by rate-limiting attack of DL-alanine as the uncharged amine (A) on the cationic (PCHO+), zwitterionic (PCHO), and anionic (PCHO-) forms of aldehyde (see Chart I). The rate of dehydration of the carbinolamine intermediates is much greater for the aldimines of 3-hydroxypyridine-4-aldehyde thanfor aldimines of pyridine-4-aldehyde suggesting the participation of the o hydroxyl group as an intramolecular catalyst. From the determined pH-dependent equilibrium constant of aldimine formation (ATpH) over the pH range 4.0-12.2, and the acid dissociation constants of DL-alanine (Kah „Rah), 3-hydroxypyridine-4-alde-hyde ('+, R'pcho), and theirproduct aldimine (Rs, Rs+, Ran+), the various equilibrium constants (R, Ru 7G) for aldimine formation were calculated (see Chart II). The increase in the concentration of aldimine in the neutral and slightly acid pH range on substitution of a hydroxyl group in the 3 position of pyridine-4-aldehyde has been demonstrated by comparing the equilibrium constant profile of DL-alanine plus 3-hydroxypyridine-4-aldehyde to that for DL-alanine plus pyridine-4-aldehyde.