烷基取代基对烷基四氢萘供氢能力影响的分子模拟

Molecular Simulation of the Impact of Alkyl Substituent on Hydrogen Donating Ability of Alkyl Tetralin

采用基于密度泛函理论的量子化学从头算法,计算了不同类型1-烷基四氢萘分子中α位C—H键断裂的反应能垒和反应热,讨论了1-烷基四氢萘的供氢能力,并考察了1-烷基四氢萘分子中烷基的链长和异构化程度对该α位C—H键断裂的影响。结果表明,与四氢萘相比,1-甲基四氢萘分子中甲基旁α位C—H键更易断裂,因此1-甲基四氢萘的供氢能力比四氢萘更强。如果1-烷基四氢萘分子中的烷基取代基不影响其旁边α位C—H键断裂产物自由基的p-π共轭,该烷基的链长及异构化程度的变化对α位C—H键断裂的影响不大,也即对1-烷基四氢萘的供氢能力的影响很小;1-叔丁基四氢萘中的叔丁基破坏了α位C—H键断裂产物自由基的p-π共轭结构,导致1-叔丁基四氢萘的供氢能力低于四氢萘。

By using the molecular simulation based on density function theory, the energy barrier and reaction heat of α position C H bond dissociation of different types of 1-alkyl tetralin were calculated to investigate the impact of alkyl substituent on the hydrogen donating ability of 1-alkyl tetralin. The impact of alkyl substituent chain length and isomerism ratio in 1-alkyl tetralins on a position C-H bond dissociation was further researched. The results indicated that in 1-methyl tetralin the α position C-H bond nearby could dissociate more easily than that in tetralin and 1-methyl tetralin would possess higher hydrogen donor activity than tetralin. If the alkyl substituent does not influence the P-π conjugation of radical, the dissociated product, the impacts of chain length and isomerism ratio of the substituent on α position C-H bond dissociation will not be obvious and the change in hydrogen donor activity will be very little. Because tert-butyl substituent in 1-tert-butyl tetralin broke the P-π conjugation of radical product, 1-tert-butyl tetralin had the lower hydrogen donor ability than tetralin.