Duarte F, Gronert S, Kamerlin SCL. Concerted or stepwise: how much do free-energy landscapes tell us about the mechanisms of elimination reactions?
J Org Chem 2014;
79:1280-8. [PMID:
24404911 PMCID:
PMC3966530 DOI:
10.1021/jo402702m]
[Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The base-catalyzed dehydration of benzene cis-1,2-dihydrodiols is driven by formation of an aromatic product as well as intermediates potentially stabilized by hyperaromaticity. Experiments exhibit surprising shifts in isotope effects, indicating an unusual mechanistic balance on the E2-E1cB continuum. In this study, both 1- and 2-dimensional free energy surfaces are generated for these compounds with various substituents, using density functional theory and a mixed implicit/explicit solvation model. The computational data help unravel hidden intermediates along the reaction coordinate and provide a novel conceptual framework for distinguishing between competing pathways in this and any other system with borderline reaction mechanisms.
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