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首页> 外文期刊>Chemistry: A European journal >Electrophilic Addition to Alkenes: The Relation between Reactivity and Enthalpy of Hydrogenation: Regioselectivity is Determined by the Stability of the Two Conceivable Products
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Electrophilic Addition to Alkenes: The Relation between Reactivity and Enthalpy of Hydrogenation: Regioselectivity is Determined by the Stability of the Two Conceivable Products

机译：烯烃的亲电子加成：反应性与氢化焓之间的关系：区域选择性由两种可能产物的稳定性决定

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摘要

Although electrophilic addition to alkenes has been well studied, some secrets still remain. Halogenations, hydrohalogenations, halohydrin formations, hydrations, epoxidations, other oxidations, carbene additions, and ozonolyses are investigated to elucidate the relation of alkene reactivities with their enthalpies of hydrogenation (H-hyd). For addition of electrophiles to unconjugated hydrocarbon alkenes, ln(k) is a linear function of H-hyd, where k is the rate constant. Linear correlation coefficients are about 0.98 or greater. None of the many previously proposed correlations of ln(k) with the properties of alkenes or with linear free-energy relationships match the generality and accuracy of the simple linear relationship found herein. A notable exception is acid-catalyzed hydration in water or in solvents stabilizing relatively stable carbocation intermediates (e.g., tertiary, benzylic, or allylic). (CNMR)-C-13 chemical shifts of the two alkene carbons also predict regioselectivity. These effects have not been noted previously and are operative in general, including addition to heteroatom-substituted alkenes.
机译：尽管对烯烃的亲电加成已经进行了充分的研究，但仍存在一些秘密。研究了卤代，氢卤代，卤代醇形成，水合，环氧化，其他氧化，卡宾加成和臭氧分解，以阐明烯烃反应性与其氢化焓（H-hyd）的关系。为了将亲电试剂加到未共轭的烃烯烃上，ln（k）是H-hyd的线性函数，其中k是速率常数。线性相关系数约为0.98或更大。 ln（k）与烯烃的性质或线性自由能关系的许多先前提出的相关性均不与本文中发现的简单线性关系的一般性和准确性相匹配。一个显着的例外是在水中或在稳定相对稳定的碳正离子中间体（例如叔，苄基或烯丙基）的溶剂中的酸催化水合作用。两个烯烃碳的（CNMR）-C-13化学位移也预测了区域选择性。这些作用以前没有被注意到，并且通常是起作用的，包括除杂原子取代的烯烃外。

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