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单词 Mesomeric effect
释义

Mesomeric effect

中文百科

中介效应

化学中的中介效应,是英国化学家克里斯托夫·英果尔德在1938年最早提出的概念,指的是通过分子共振式定量判断得出的、取代基的一种吸电子/给电子性质。M 指具吸电子性的取代基(如 CH3C(O)-、-CN、-NO2);+M 则指给电子性的取代基(如 -OH、-NH2)。

IUPAC 金皮书的定义:取代基因其 p- 或 π- 轨道与分子实体其他部分的 p- 或 π- 轨道发生重叠,而引起的分子在反应速率、电离平衡等方面发生的变化。

英语百科

Mesomeric effect 中介效应

The mesomeric effect in chemistry is a property of substituents or functional groups in a chemical compound. The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structures and is symbolized by the letter M. The mesomeric effect is a permanent effect and operates in compounds containing at least one double bond and another double bond or a lone pair separated by a single bond. The mesomeric effect is negative (–M) when the substituent is an electron-withdrawing group and the effect is positive (+M) when based on resonance and the substituent is an electron releasing group.

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更新时间:2025/6/21 12:25:53