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Development of Structure-Reactivity Relationship

结构-反应关系的发展

基本信息

批准号：
07454251
负责人：
MISHIMA Masaaki
金额：
$ 0.77万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454251/
关键词：
substituent effect Yukawa-Tsuno equation resonance demand gas-phase ion vinyl cation benzylic carbocation aromatic radical anion ab initio MO calculation 構造-反応性相関気相置換基効果ラジカルアニオンの安定性気相イオン-分子反応 FTICR

项目摘要

(1) Substituent effects on the stability of aromatic radical anions measured by electron affinities of benzaldehydes, acetophenones, methyl benzoates, benzophenones, and nitrobenzenes were analyzed by means of the Yukawa-Tsuno (Y-T) equation. It has been shown that resonance demand parameter (r) varies significantly with the system from 0.62 for nitrobenzene, via 1.11 for benzaldehyde, to 1.29 for methyl benzoate series. The increasing order of the r value is in agreement with decreasing stability of a parent radical anion. This trend is consistent with that observed for benzylic carbocations.(2) Gas-phase basicities (GB) of m, p-substituted phenylacetylenes having the CF_3, t-Bu, Me, or H group at the beta-position have been determined based on proton-transfer equilibria. The analysis of the substituent effects on the GB values based on the Y-T equation showed that the resonance demand of the vinyl cation increases with the decreasing stability of the unsubstituted member of respective series. It was found that there is a good linear relationship between the r values and the stabilities of the respective parent cations, including the benzylic carbocation series, suggesting that the resonance demand is a parameter inherent in the structure of a carbocation.(3) In order to corroborate the characterization of the resonance demands for the carbocation radical anion systems, ab initio MO calculations were performed. It was found that the changes of structural parameters such as a bond length in the carbocation system are in consistent with the resonance theory and that those are linearly correlated with the resonance demand observed for gas-phase ions. In conclusion, the empirical r value determined by the Y-T correlation should have real physical meaning which represents the degree of pi-delocalization of the positive charge.

(1)用Yukawa-Tsuno（Y-T）方程分析了取代基对苯甲醛、苯乙酮、苯甲酸甲酯、二苯甲酮和硝基苯等芳香自由基阴离子稳定性的影响。结果表明，共振需求参数（r）随体系的变化很大，硝基苯为0.62，苯甲醛为1.11，苯甲酸甲酯为1.29。r值的增加顺序与母体自由基阴离子的稳定性降低一致。这一趋势与苄型碳正离子的观察结果一致。(2)本文用质子转移平衡法测定了β位含CF_3、t-Bu、Me或H的间、对位取代苯乙炔的气相碱性。基于Y-T方程分析了取代基对GB值的影响，结果表明，随着取代基稳定性的降低，乙烯基阳离子的共振需求增大。结果发现，有一个良好的线性关系的r值和各自的母阳离子，包括苄基碳阳离子系列的稳定性，这表明共振需求是一个碳阳离子的结构中固有的参数。(3)为了证实碳正离子自由基阴离子体系共振需求的表征，进行了从头算MO计算。结果发现，碳正离子体系中的键长等结构参数的变化与共振理论一致，并且与气相离子的共振需求呈线性相关。因此，由Y-T关系确定的经验r值应具有真实的物理意义，它代表正电荷的π离域程度。