The 4 K radiolysis of linear alkanes as studied by electron spin resonance spectroscopy: selective formation of terminal alkyl radicals in the primary process
The 4 K radiolysis of linear alkanes as studied by electron spin resonance spectroscopy: selective formation of terminal alkyl radicals in the primary process
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电子自旋共振光谱研究直链烷烃的 4 K 辐射分解：初级过程中末端烷基自由基的选择性形成
DOI：
10.1021/j100270a032
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
K. Nunome
中科院分区：
文献类型：
--
作者：
M. Iwasaki;K. Toriyama;M. Fukaya;H. Muto;K. Nunome
总的来说，这些氰酸甲酯和异氰酸酯的气相离子化学是简单的，并且，也许令人惊讶的是，没有观察到广泛的缩合反应。已知异氰酸甲酯在液相中经历快速和放热的缩合反应，但在气相中似乎不是这种情况。从ICR实验和计算中得到的硫氰酸甲酯和异硫氰酸甲酯的质子亲合能值十分相似。考虑到两种质子化分子结构的差异，特别是CH 3SCN中质子化的有利位点显然是氮，而CH 3 NCS中硫似乎稍微有利，这是相当令人惊讶的。此外，质子化的CH_3SCN中质子与CN键形成的角接近180 °，而在CH_3 NCS中H+ SC角为95 °。因此，很难相信这两种异构体的质子亲合力的相似性是由分子的某些固有性质引起的，而不仅仅是巧合。CHNCS和CHSCN基团具有彼此小于5 kcal/mol的质子亲和力。然而，在这种情况下，相似性也归因于巧合。
On the whole, the gas-phase ion chemistry of these methyl cyanates and isocyanates is straightforward, and, perhaps sur-prisingly, no extensive condensation reactions were observed. Methyl isocyanate is known to undergo rapid and exothermic condensation reactions in the liquid phase, but this does not appear to be the case in the gas phase. The values obtained for the proton affinities of methyl thio-cyanate and methyl isothiocyanate from boththe ICR experiments and from the calculations are quite similar. Considering the differences in the structures of the two protonated molecules, and especially the factthat the favored site of protonation in CH3SCN is clearly the nitrogen while in CH3NCS the sulfur appears to be slightly favored, this is rather surprising. Furthermore, the angle the proton formswith the CN bond in protonated CH3SCN is closeto 180, while in CH3NCS the H+ SC angle is 95. Therefore, it is hard to believe that the similarity in the proton affinities of the two isomers arises from some inherent property of the molecules and is not merely coincidental. The CHNCS and CHSCN radicals have proton affinities which are within less than 5 kcal/mol of each other. However, in this case too, the similarity is attributed to a coincidence.