Electron spin resonance study on the acrylic acid anion radical and its protonation in some irradiated frozen solutions
Electron spin resonance study on the acrylic acid anion radical and its protonation in some irradiated frozen solutions
复制标题
某些辐照冷冻溶液中丙烯酸阴离子自由基及其质子化的电子自旋共振研究
DOI：
--
复制
发表时间：
1973
期刊：
影响因子：
--
通讯作者：
H. Muto
中科院分区：
文献类型：
--
作者：
M. Iwasaki;M. Fukaya;S. Fujii;H. Muto
对电子与丙烯酸(AA)在各种辐照冷冻溶液中的反应进行了ESR研究。在2-甲基四氢呋喃(MTHF)、三乙胺(TEA)和3-甲基己烷(MHX)等基质中发现了丙烯酸的电子加合物[CH2-CH-COOH]-。CH2质子末端的超精细耦合(αo约等于13G)与离域阴离子pi自由基的INDO分子轨道计算是一致的。冻结的MTHF-AA溶液在97℃的辐照后热退火导致电子加合物质子化，形成氢加成自由基STACH3-CH-COOH！。在115℃左右，在TEA基质中也观察到了相同的转化率，而在MHX基质中没有观察到转化。自由基的转化似乎与冻结的MTHF的宽线MMR测量的谱线宽度突然变化所发现的基质中的分子重取向有关。另一方面，在一些含有极性质子的基质中，如醇和碱性水溶液中，在辐照后立即发现了氢加成自由基。结果表明，丙烯酸的电子加合物既可以以分子阴离子形式稳定，也可以以质子化形式稳定，这取决于基质分子的性质，氢加成自由基是由极性质子转移到电子加合物上形成的。提出了一个质子化阳离子通过氢键进行质子转移的模型，用于MTHF和TEA基质中电子加合物的质子化。
An ESR study has been carried out for reactions of electrons with acrylic acid (AA) in a variety of irradiated frozen solutions. The electron adducts of acrylic acid [CH2-- CH--COOH]- were found to be formed in some matrices, such as 2-methyltetrahydrofuran (MTHF), triethylamine (TEA), and 3-methylhexane (MHX). The hyperfine couplings to the end CH2 protons ( alpha o approx equal 13 G) are consistent with the INDO MO calculation made for the delocalized anion pi radical. The post-irradiation thermal annealing of the frozen MTHF-AA solutlons at 97 deg K resulted in protonation of the electron adducts to form the hydrogen addition radical STACH3--CH-COOH!. The same conversion was also observed in the TEA matrices at around 115 deg K, while no conversion was observed in the MHX matrices. The radical conversion seems to be associated with the molecular reorieniations in the matrices which were found from the sudden change of the line width in the wide-line mmr measurements of frozen MTHF. On the other hand, the hydrogen addition radicals were found immediately after irradiation in some matrices containing polar protons such as alcohols and alkaline aqueous solutions. It is concluded that the electron adducts of acrylic acid can be stabilized eithermore » in a molecular anion or in its protonated form, depending upon the nature of the matrix molecules and that the hydrogen addition radicals are formed from the polar proton transfer to the electron adducts. A model of proton transfer from protonated cations via the hydrogen bond is proposed for protonation of the electron adducts in the MTHF and TEA matrices.« less