Premium
Solvation effects in the heterolyses of 3‐X‐3‐methylpentanes (X = Cl, Br, I)
Author(s) -
Martins Filomena,
Leitão Ruben Elvas,
Moreira Luís
Publication year - 2004
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.816
Subject(s) - chemistry , solvation , nucleophile , heterolysis , electrophile , iodide , polarizability , hydrogen bond , chloride , medicinal chemistry , solvent , computational chemistry , inorganic chemistry , photochemistry , organic chemistry , molecule , catalysis
Abstract A comparative study of the heterolysis reactions of 3‐X‐3‐methylpentanes (X = Cl, Br, I) in a set of protic and aprotic solvents was performed at 25.00°C. Rate constant values were correlated with solvent descriptors using the TAKA multiparametric equation. Our results point towards a decrease in both hydrogen bond donor acidity (electrophilicity) and hydrogen bond acceptor basicity (nucleophilicity) contributions, and towards an increase in the dipolarity/polarizability term on going from the chloride substrate to iodide. These features suggest the formation of an increasingly early transition state, in contrast to the classical Hughes–Ingold rationale, but in agreement with the Hammond postulate. Furthermore, there seems to be no evidence for a shift in solvation from an electrophilic (or anionic) mode in the chloride substrate to a nucleophilic (or cationic) mode in the iodide, as claimed by some authors. Copyright © 2004 John Wiley & Sons, Ltd.