STUDIES OF CAGE REACTIONS .I. NEED FOR REFINED MODELS . COMBINATION OF CF3 RADICALS
STUDIES OF CAGE REACTIONS .I. NEED FOR REFINED MODELS . COMBINATION OF CF3 RADICALS
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DOI：
10.1021/ja01004a012
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发表时间：
1968-01-01
影响因子：
15
通讯作者：
SZWARC, M
中科院分区：
文献类型：
--
作者：
DOBIS, O;PEARSON, JM;SZWARC, M
研究了CF_3N = NCF_3在14种溶剂中光解形成的CF_3自由基在4种不同温度下的笼状结合。结合的概率，p（CF 3）= C2 F6/N2，随着温度的降低和溶剂粘度的增加而增加。与Noyes的方法一致，对于每种溶剂，jp（CF 3）是f21的线性函数。对于不同的溶剂，得到略微不同的线。似乎Noyes模型中没有考虑的其他因素阻碍了这种结合，并且在粘性较低的介质中其影响变得更加明显。因此，绘制了I/pfCF）与I/pfCF的曲线图。对于所有研究的溶剂和温度获得的粘度曲线给出了一条在低粘度区域向上弯曲的线。log P（CF 3）对1 jT的曲线也是线性的。P（CF 3）=（C2 F6/N2）/[1-（C2 F6/N2）]= kc/kd是笼结合和从笼逃逸的概率的比率。值得注意的是，对于所有溶剂获得的线是平行的，这意味着形式“活化能”差Ee-艾德是恒定的。相反，粘度的“活化能”随着溶剂变得更粘而增加。这些结果的意义进行了讨论。它们似乎表明每次碰撞的组合概率a很小，对于大多数研究的溶剂来说，在0.3到0.1之间。各种因素，应包括在一个更全面的模型概述。
The cage combination of CF3 radicals formed by photolysis of CF3N= NCF3 was investigated at four different temperatures in 14 solvents. The probability of combination, p (CF3)= C2F6/N2, increases with decreasing temperature and increasing viscosity of the solvent. In agreement with Noyes’ approach, for each solvent 1 jp {CF3) is a linear function of/21. Slightly different lines are obtained for different solvents. It seems that some other factor, not considered in Noyes’ model, hindersthe combination, and its effect becomes more pronounced in less viscous media. Consequently, a plot of l/pfCFs) vs.''-obtained for all the investigated solvents and temperatures gives a line which curves up in the regions of low viscosities. The plots of log P (CF3) vs. 1 jT are also linear. P (CF3)=(C2F6/N2)/[1—(C2F6/N2)]= kc/kd is the ratio of probabilities of cage combination and of escape from the cage. It is remarkable that the lines obtained for all the solvents are parallel, implying that the formal “activation energy” difference, Ee— Ed, is constant. In contradistinction, the “activation energy” of viscosity increases as the solvent be-comes more viscous. The significance of these results is discussed. They seem to indicate that the probability, a, of combination on each collision is small, being between 0.3 and 0.1 for most of the investigated solvents. Var-ious factors which should be included in a more comprehensive model are outlined.