CARBON ISOTOPIC FRACTIONATION IN THE SCHMIDT DECARBOXYLATION: EVIDENCE FOR TWO PATHWAYS TO PRODUCTS
CARBON ISOTOPIC FRACTIONATION IN THE SCHMIDT DECARBOXYLATION: EVIDENCE FOR TWO PATHWAYS TO PRODUCTS
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施密特脱羧中的碳同位素分馏：两种产物途径的证据
DOI：
10.1021/jo01335a014
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
J. Hayes
中科院分区：
文献类型：
--
作者：
E. Vogler;J. Hayes
在CHCl/sub 3/中，正辛酸与HN/sub 3/在H/sub 2/SO/sub 4/-催化下的反应（施密特脱羧反应）中，CO/sub 2/ at 5 +- 2/sup 0/C的生成分两个动力学阶段进行，具有不同的碳动力学同位素效应.实验在高效搅拌条件下在HN/sub 3/浓度范围为1.47至0.24 M下进行。在初始HN/sub 3/浓度为1.47 M时，第一动力学阶段的假一级速率常数为0.07 +- 0.03 h/sup-1/，其中/sup 12/k//sup 13/k = 1.0589 +- 0.0003。在48分钟的滞后时间之后，CO/sub 2/放出速率改变，其中伪一级速率常数（1.47 M HN/sub 3/）增加到0.45 +- 0.02 h/sup-1/; /sup 12/k//sup 13/k约。= 1.03。在较低的HN/sub 3/浓度下获得的结果表明，第一，较慢的反应相显示整体一级动力学，其速率是独立的HN/sub 3/浓度。在H/sub 2/SO/sub 4/中加入KHSO/sub 4/可抑制第一反应相。HN/sub 3//CHCl/sub 3/与H/sub 2/SO/sub 4/的预平衡显著影响初始CO/sub 2/产物的同位素组成，通过H/sub 2/SO/sub 4/对HN/sub 3/的作用明显影响第二相反应more »途径的初始瞬时利用。虽然动力学阶段不能在22/sup 0/C下解析，但生成的CO/sub 2/的同位素组成表明，两种产物途径都被利用。两张图两张表。«少
The evolution of CO/sub 2/ at 5 +- 2/sup 0/C from the H/sub 2/SO/sub 4/-catalyzed reaction of n-octanoic acid with HN/sub 3/ in CHCl/sub 3/ (the Schmidt decarboxylation) takes place in two kinetic phases with different carbon kinetic isotope effects. Experiments were carried out under high-efficiency stirring conditions at HN/sub 3/ concentrations ranging from 1.47 to 0.24 M. At an initial HN/sub 3/ concentration of 1.47 M, the pseudo-first-order rate constant for the first kinetic phase was 0.07 +- 0.03 h/sup -1/, with /sup 12/k//sup 13/k = 1.0589 +- 0.0003. After a lag time of 48 minutes the rate of CO/sub 2/ evolution changed, with the pseudo-first-order rate constant (1.47 M HN/sub 3/) increasing to 0.45 +- 0.02 h/sup -1/; /sup 12/k//sup 13/k approx. = 1.03. Results obtained at lower HN/sub 3/ concentrations showed that the first, slower reaction phase displayed overall first-order kinetics, its rate being independent of HN/sub 3/ concentration. The first reaction phase could be suppressed by addition of KHSO/sub 4/ to the H/sub 2/SO/sub 4/. Preequilibration of the HN/sub 3//CHCl/sub 3/ with H/sub 2/SO/sub 4/ markedly affected the isotopic composition of the initial CO/sub 2/ product, apparently effecting the initial transient utilization of the second-phase reactionmore » pathway through the action of the H/sub 2/SO/sub 4/ on the HN/sub 3/. Although the kinetic phases could not be resolved at 22/sup 0/C, the isotopic composition of the evolved CO/sub 2/ indicated that both pathways to the product were being utilized. 2 figures, 2 tables.« less