Premium
A DFT study of transition structures and reactivity in solvolyses of tert ‐butyl chloride, cumyl chlorides, and benzyl chlorides
Author(s) -
Ruff Ferenc,
Farkas Ödön
Publication year - 2008
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1284
Subject(s) - chemistry , substituent , nucleophile , reactivity (psychology) , medicinal chemistry , solvolysis , transition state , chloride , solvent effects , hammett equation , reaction rate constant , hydrolysis , benzyl chloride , solvent , computational chemistry , kinetics , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics
DFT computations were performed on the S N 1 and S N 2 solvolyses of substituted cumyl chlorides and benzyl chlorides in ethanol and water, by increasing stepwise the CCl distance and by optimization. The total energy increases with the increase in the ClC distance in S N 1 reactions, while free energy of activation pass through maximum. To validate the results, the calculated free energies of activation were compared with data obtained by kinetic measurements. The structural parameters of the transition states were correlated with the Hammett substituent constants and compared with the data of hydrolyses of tert ‐butyl chloride and methyl chloride, which proceed with known mechanisms. Conclusions on the mechanisms of the reactions were driven from the effect of substituents on free energies of activation. Cumyl chlorides substituted with electron‐donating (e‐d) groups solvolyze with S N 1 mechanism, while the reactions of substrates that bear electron‐withdrawing groups proceed with weak nucleophilic assistance of the solvent. Benzyl chlorides hydrolyze through an S N 2 pathway except those derivatives that have strongly e‐d groups, where the reaction has S N 1 character, but a weak nucleophilic assistance of the water should also be taken into consideration. Copyright © 2007 John Wiley & Sons, Ltd.