Molecular Salt Effects in the Gas Phase: Tuning the Kinetic Basicity of [HCCLiCl]− and [HCCMgCl2]− by LiCl and MgCl21. Issue 41 (30th July 2014)

• Record Type: Journal Article
• Authors: Khairallah, George N.; da Silva, Gabriel; O'Hair, Richard A. J.
• Is Part Of: Angewandte Chemie international edition. Volume 53:Issue 41(2014)
• Page Start: 10979
• Page End: 10983
• Publication Date: 2014-07-30
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201404362
• Languages: English
• ISSNs: 1433-7851

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>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. [HCCLiCl]⁻ reacts with water more rapidly than [HCCMgCl₂]⁻, consistent with the higher reactivity of organolithium versus organomagnesium reagents. Addition of LiCl to [HCCLiCl]⁻ or [HCCMgCl₂]⁻ enhances their reactivity towards water by a factor of about 2, while addition of MgCl₂ to [HCCMgCl₂]⁻ 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.</p> </abstract>