Elevated reaction order of 1,3,5-tri-tert-butylbenzene bromination as evidence of a clustered polybromide transition state: a combined kinetic and computational study

Andrey V. Shernyukov, Alexander M. Genaev, George E. Salnikov, Vyacheslav G. Shubin, Henry S. Rzepa

Результат исследования: Научные публикации в периодических изданияхстатья

Аннотация

The kinetics and mechanism of concurrent bromo-de-protonation and bromo-de-tert-butylation of 1,3,5-tri-tert-butylbenzene at different bromine concentrations were studied experimentally and theoretically. Both reactions have high order in bromine (experimental kinetic orders ∼5 and ∼7, respectively). According to quantum chemical DFT calculations, such high reaction orders are caused by participation of clustered polybromide anions Br 2n−1 - in transition states. Bromo-de-tert-butylation has a higher order due to its bigger reaction center demanding clusters of extended size. A significant primary deuterium kinetic isotope effect (KIE) for bromo-de-protonation is measured indicating proton removal is rate limiting, as confirmed by computed DFT models. The latter predict a larger value for the KIE than measured and possible explanations for this are discussed.

Язык оригиналаанглийский
Страницы (с-по)3781-3789
Число страниц9
ЖурналOrganic and Biomolecular Chemistry
Том17
Номер выпуска15
DOI
СостояниеОпубликовано - 21 апр 2019

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