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首页> 美国政府科技报告 >Substitution Effects and Linear Free Energy Relationships during Reduction of 4-Benzoyl-N-(4-substituted benzyl) Pyridinium Cations
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Substitution Effects and Linear Free Energy Relationships during Reduction of 4-Benzoyl-N-(4-substituted benzyl) Pyridinium Cations

机译：还原4-苯甲酰基-N-（4-取代苄基）吡啶鎓阳离子时的取代效应和线性自由能关系

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摘要

In analogy to 4-b-substituted benzoyl)-N-methylpyridinium cations (1 -X's), the title species (2-X's, -X = -0CH3, -CH3, -H, -Br, -COCH3, -N02) undergo two reversible, well-separated (E1/2 greater than mV) one-electron reductions. The effect of substitution on the reduction potentials of 2-X's is much weaker than the effect of the same substituents on 1-X's: the Hammett p-values are 0.80 and 0.93 for the 1st- and 2nd-e reduction of 2-X's vs. 2.3 and 3.3 for the same reductions of 1-X's, respectively. Importantly, the nitro group of 2-NO2 undergoes reduction before the 2nd-e reduction of the 4- benzoylpyridinium system. These results suggest that the redox potentials of the 4-benzoylpyridinium system can be course-tuned via p-benzoyl substitution and fine-tuned via p-benzyl substitution. Introducing the recently derived substituent constant of the -N02 group (cp-No2 = -0.97) yields an excellent correlation for the 3rd-e reduction of 2- NO2 (corresponding to the reduction of the carbonyl group) with the 2rd-e reduction of the other 2-X's, and confirms the electron donating properties of -N02.

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