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Pressure Effects in the Solvolysis of Benzyl Chlorides
Author(s) -
Laidler K. J.,
Martin R.
Publication year - 1969
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550010111
Subject(s) - chemistry , solvolysis , acetone , mole fraction , benzyl chloride , solvent , chloride , analytical chemistry (journal) , medicinal chemistry , organic chemistry , catalysis , hydrolysis
Rates of solvolysis of benzyl chloride and of substituted benzyl chlorides have been measured in an acetone‐water mixture (acetone mole fraction 0.147) at pressures ranging from atmospheric to 1 kbar. Pressure studies have also been made for p ‐methyl benzyl chloride in various acetone‐water mixtures. Measurements have also been made of the partial molar volumes of the reactants. The plots of log k against pressure are fitted to a second‐degree polynomial in P , and values of Δ V ‡ and (δΔ V / /δ P ) T are obtained. The Δ V ‡ values are all negative, having values ranging from −18 to −24 cc/mole. The results are interpreted on the view that the mechanisms are S N 2(1), i.e. are towards the S N 1 end of the S N 2 spectrum of behavior. The Δ V ‡ values steadily become more negative in the series p CH 3 , H, p Cl, p NO 2 , and this is interpreted in terms of the greater spreading of positive charge in the p CH 3 case and in terms of greater S N 2(2) character in the p NO 2 case. The Δ V ‡ values go through a minimum as the solvent composition is varied, a result that is related to the existence of a corresponding maximum in the partial molar volumes of the reactant. The (δΔ V ‡ /δ P ) T values show a negative correlation with Δ V ‡ , suggesting, as expected, that the more compact activated complexes are the least compressible.