Reactivities of conjugated dienes to arylthiyl radicals
Reactivities of conjugated dienes to arylthiyl radicals
复制标题
共轭二烯与芳硫基自由基的反应活性
DOI：
10.1021/jo00255a017
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
M. Matsuda
中科院分区：
文献类型：
--
作者：
O. Ito;S. Tamura;K. Murakami;M. Matsuda
用闪光光解法测定了芳硫基自由基与各种共轭二烯加成反应的速率常数。对于每个芳硫基自由基，1，3-丁二烯的绝对速率常数接近苯乙烯，比1-己烯大约1倍。3500;烯丙基型自由基的共振稳定化的形成加速了反应速率。Hammett关系与不同的取代基上的芳硫基自由基进行了检查，为每个二烯;氯和羧基取代二烯减少共轭双键的电子密度由于诱导效应，反之亦然的甲基和甲氧基取代基。在二烯的末端碳的取代降低了反应性;末端位置主要受到芳硫基自由基的攻击。2，3-二甲氧基-1，3-丁二烯的反应活性明显低于2，3-二甲基衍生物，表明前者的二烯为角构象。
The rate constants for the addition reactions of the arylthiyl radicals to various conjugated dienes have been determined by the flash photolysis method. For each arylthiyl radical, the absolute rate constant of 1, 3-butadiene is close to that of styrene and is larger than that of 1-hexene by a factor of ca. 3500; the formation of the resonance stabilization of the allyl-type radical accelerates the reaction rate. The Hammett relation with varying substituents on the arylthiyl radicals was examined for each diene; the chloro and carboxylic substitutions on diene reduce the electron density of the conjugated double bond due to the inductive effect, vise versa for the methyl and methoxy substituents. The substitution at the terminal carbon of diene decreases the reactivity; the terminal position is predominantly attacked by the arylthiyl radical. The reactivity of 2, 3-dimethoxy-1, 3-butadiene is considerably lower than that of the 2, 3-dimethyl derivative, suggesting an angular conformation for the former diene.