Proton Hyperfine Interactions in Paramagnetic Resonance of Semiquinones1
Proton Hyperfine Interactions in Paramagnetic Resonance of Semiquinones1
复制标题
半醌顺磁共振中的质子超精细相互作用1
DOI：
10.1021/ja01615a010
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发表时间：
1955
影响因子：
15
通讯作者：
G. Fraenkel
中科院分区：
文献类型：
--
作者：
B. Venkataraman;G. Fraenkel
.本文用顺磁共振吸收光谱法研究了在碱性介质中对苯二酚氧化或醌还原生成的半醌。首次在溶液中观察到对苯醌离子;通过检查其顺磁共振谱的结构，确定了它的存在。在自由基的顺磁共振谱中观察到的某些结构是由于分子内未成对电子和质子之间的磁超精细相互作用引起的。发现对-苯醌离子的超精细相互作用常数的大小为6.54±0.06 Me/秒，测得杜洛半醌离子的常数为5.28± 0.15Me/秒虽然对相互作用常数大小的理论解释还不令人满意，但我们相信，这些常数的相对值可以用质子处的相对奇电子密度来解释。durosemiquinone离子中的超精细相互作用的大小可以代表超共轭现象的直接确认。对甲苯二醌离子、9，10-菲二醌离子和苯偶酰与苯偶姻混合物形成的自由基进行了顺磁谱观察。有证据表明，暴露在空气中的对苯醌的碱性醇溶液中存在两个或更多的自由基。
. Semiquinones formedby the oxidation of hydroquinones or the reduction of quiñones in alkaline media havebeen studied by paramagnetic resonance absorption spectroscopy. The p-benzosemiquinone ion has been observed for the first time in solution; its existence has been established by examination of the structure of its paramagnetic resonance spectrum. It has been confirmed that certain structure observed in the paramagnetic resonance spectra of some free radicals is due to intra-molecular magnetic hyperfine interaction between the unpaired electron and protons. The magnitude of the hyperfine interaction constant for the^-benzosemiquinone ion was found to be 6.54±0.06 Me./sec., and the magnitude of the con-stant for the durosemiquinone ion was found to be 5.28±0.15 Me./sec. Although theoretical interpretation of the mag-nitude of the interaction constants has not been satisfactory, it is believed that relative values of these constants can be interpreted in terms of relative odd-electron densities at the protons. The magnitude of the hyperfine interaction in the durosemiquinone ion may represent direct confirmation of the phenomenon of hyperconjugation. Paramagnetic spectra were observed from the/>-tolusemiquinone ion, the 9, 10-phenanthrenesemiquinone ion, and the radical formed from a mixture of benzil and benzoin. Evidence was found for the existence of two or more radicals in an alkaline alcoholic solution of p-benzoquinone exposed to the air.