Solvent and substituent on the thermal isomerization of substituted azobenzenes. Flash spectroscopic study
Solvent and substituent on the thermal isomerization of substituted azobenzenes. Flash spectroscopic study
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DOI：
10.1021/ja00737a027
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发表时间：
1971-04
影响因子：
15
通讯作者：
D. Whitten;P. Wildes;J. G. Pacifici;G. Irick
中科院分区：
文献类型：
--
作者：
D. Whitten;P. Wildes;J. G. Pacifici;G. Irick
研究了对位给体/对位受体取代偶氮苯[如4-(二乙氨基)-4‘-硝基偶氮苯]的热异构化反应。其中几种染料的热异构化速度比测得的偶氮苯及其单取代衍生物的热异构化速度快得多。对热异构化反应速率和活化能的较大溶剂效应的观察表明，这些偶氮苯可能是通过旋转机制作用的。偶氮苯的热异构化和光化学异构化一直是人们研究的主题。与二苯乙烯类化合物不同，二苯乙烯类化合物具有相当大的热异构化活化能，因此在常温下以离散的、可分离的异构体形式存在，而偶氮苯在室温下很容易异构化(活化能约为23千卡/摩尔)6。偶氮苯的易热异构化反应机理仍在研究中。
Thermal isomerization of some para-donor/para'-acceptor-substituted azobenzenes [for example, 4-(diethylamino)-4'-nitroazobenzene] was studied by observing relaxation to equilibrium following flash photolysis. Several of these dyes showmuch faster rates of thermal isomerization than those measured for azobenzene and its monosubstituted derivatives. The observation of sizable solvent effects on the rates and activation energies for thermal isomerization suggests that a rotational mechanism might be operative for these azobenzenes. he thermal and photochemical isomerization of azobenzenes has been the subject of much investi-gation. 6-12 In contrast to the stilbenes which show sizable activation energies for thermal isomerization and thus exist as discrete, isolable isomers at ordinary temperatures, azobenzenes are readily isomerized (activation energies ca. 23 kcal/mol) 6 at room tempera-ture. The mechanism of the facile thermal isomeriza-tion of azobenzene is still the subject of investigation.