ESR Studies on Radical Conversions in Irradiated Single Crystals of Succinic Acid
ESR Studies on Radical Conversions in Irradiated Single Crystals of Succinic Acid
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琥珀酸单晶辐照自由基转化的 ESR 研究
DOI：
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发表时间：
1972
期刊：
影响因子：
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通讯作者：
M. Iwasaki
中科院分区：
文献类型：
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作者：
H. Muto;Tetsushi Inoue;M. Iwasaki
在富马酸掺杂晶体的帮助下，对辐照琥珀酸单晶中从初级自由基到室温稳定自由基的自由基转化进行了ESR研究。由于在掺杂的晶体中，琥珀酸阴离子的光谱被富马酸阴离子的光谱所取代，因此有可能识别出由CH 3 H2 CH 2COOH产生的光谱，该光谱长期以来一直被假定为室温稳定的自由基CH 3 HCOOH的前体。进一步发现，在− 100°C时，一部分H2 CH 2COOH转化为HOOC H2 CH 2COOH，然后在− 100 ° C至− 75° C发生自由基异构化反应，从H2 CH 2COOH到CH 3CHCOOH发生构象变化，这有利于分子内氢转移。新鲜形成的CH 3CHCOOH自由基具有不同的构象，从室温下稳定的物种。稳定构象是通过在不稳定空间中CH和羧基碳原子之间的C-C键的180°旋转实现的。
The ESR studies on the radical conversions from primary to room temperature stable radicals in irradiated single crystals of succinic acid have been carried out with aid of fumaric acid‐doped crystals. Since in the doped crystals the spectrum of succinic acid anion was replaced by that of furmaric acid anion, it was possible to identify the spectrum arising from ĊH2CH2COOH, which has been postulated for a long time as a precursor of the room temperature stable radical CH3ĊHCOOH. It has been further found that a part of ĊH2CH2COOH converts into HOOCĊHCH2COOH at − 100°C and then the radical isomerization from ĊH2CH2COOH to CH3CHCOOH takes place at − 100 − ∼ − 75° C following the conformational change which is favorable to the intramolecular hydrogen transfer. The freshly formed CH3CHCOOH radical has a different conformation from that of the room temperature stable species. The stable conformation is achieved by the 180° rotation around the C–C bond between the CH and carboxyl carbon atoms in the unstable sp...