Viscosity dependence of bond homolysis. Qualitative and semiquantitative test for cage return

Viscosity dependence of bond homolysis. Qualitative and semiquantitative test for cage return
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键均裂的粘度依赖性。

DOI：
10.1021/ja00721a019
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发表时间：
1970
期刊：
影响因子：
--
通讯作者：
Kennedy Smith
Kennedy Smith
中科院分区：
--
文献类型：
--
作者：
W. Pryor;Kennedy Smith

文献摘要

被引文献

相似文献

在一系列不同粘度的烷烃溶剂中测定了各种自由基引发剂的分解速率常数。这些观察到的速率常数的粘度依赖性提出作为一个测试，允许引发剂分为两类。单键引发剂，即最初只断开一个键而分解的引发剂，其粘度常数随溶剂粘度的增加而减小。多键引发剂，即那些通过一个以上的键的断裂而分解的引发剂，已经观察到与溶剂粘度无关的速率常数。此定性测试已被应用到偶氮引发剂，过酸酯，和过氧化物，并与文献中的相关数据的结果进行了比较。本文提出了一个方程，它定量地把引发剂分解的速率常数与溶剂粘度联系起来。该方程用于估算几种引发剂的k 0 b> d/ki，其中ki是真实的单分子均裂速率常数。Martin和Koenig用氧-18扰乱技术报道了koh、ilki值，并将我们的粘度处理所得值与这些文献值进行了比较。数量协议是公平的。然而，粘度法似乎有可能进一步改进和发展。
The rate constants for decomposition of a wide variety of free-radical initiators have been determined in a series of alkane solvents of varying viscosities. The viscosity dependence of these observed rate constants is proposed as a test to allow initiators to be divided into two classes. One-bond initiators, ie, those which decom-pose by the initial scission of only one bond, have observedrate constants that decrease as the solvent viscosity in-creases. Multibond initiators, ie, those that decompose by the simultaneousscission of more than one bond, have observed rate constants that are independent of the solvent viscosity. This qualitative test has been applied to azo initiators, peresters, and peroxides, and the results are compared with related data from the literature. An equation has been developed which quantitatively relates the observed rate constant for decomposition of an initia-tor to the solvent viscosity. This equation is used to estimate k0b> d/ki for several initiators, where ki is the true unimolecular homolysisrate constant. Values of koh, ilki have been reported by Martin and byKoenig using oxy-gen-18 scrambling techniques, and values derived from our viscosity treatment are compared with these literature values. The quantitative agreement is onlyfair. However, it appears possible that the viscosity method can be refined and developed further.