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Molecular Salt Effects in the Gas Phase: Tuning the Kinetic Basicity of [HCCLiCl] − and [HCCMgCl 2 ] − by LiCl and MgCl 2
Author(s) -
Khairallah George N.,
da Silva Gabriel,
O'Hair Richard A. J.
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201404362
Subject(s) - chemistry , reactivity (psychology) , kinetic energy , acetylene , kinetics , reagent , reaction mechanism , ab initio , enthalpy , computational chemistry , adduct , reaction rate constant , inorganic chemistry , thermodynamics , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics
Abstract A combination of gas‐phase ion–molecule reaction experiments and theoretical kinetic modeling is used to examine how a salt can influence the kinetic basicity of organometallates reacting with water. [HCCLiCl] − reacts with water more rapidly than [HCCMgCl 2 ] − , consistent with the higher reactivity of organolithium versus organomagnesium reagents. Addition of LiCl to [HCCLiCl] − or [HCCMgCl 2 ] − enhances their reactivity towards water by a factor of about 2, while addition of MgCl 2 to [HCCMgCl 2 ] − enhances its reactivity by a factor of about 4. Ab initio calculations coupled with master equation/RRKM theory kinetic modeling show that these reactions proceed via a mechanism involving formation of a water adduct followed by rearrangement, proton transfer, and acetylene elimination as either discrete or concerted steps. Both the energy and entropy requirements for these elementary steps need to be considered in order to explain the observed kinetics.