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Cross interaction constants as a measure of the transition state structure. 13. Steric effects of the N , N ‐dimethyl group on the transition state structure in aminolysis of alkyl benzenesulphonates
Author(s) -
Lee Ikchoon,
Rhyu Keun Woo,
Lee Hai Whang,
Shim Chang Sub,
Oh Hyuck Keun
Publication year - 1990
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.610031109
Subject(s) - chemistry , steric effects , aminolysis , acetonitrile , nucleophile , methanol , leaving group , computational chemistry , transition state , reaction rate constant , stereochemistry , kinetics , organic chemistry , catalysis , physics , quantum mechanics
Kinetic studies on the reactions of methyl (MBS) and ethyl benzenesulphonates (EBS) with N , N ‐dimethylanilines (DMA) in methanol and acetonitrile are reported. The cross interaction constants ρ XZ and β XZ , between the substituents in the nucleophile (X) and the leaving group (Z) indicated that the transition states (TS) are looser than those for the reactions with anilines, but the relative tightness between the two substrates was the same; the TS was tighter for EBS despite the increase in steric effect leading to looser TSs for MBS and EBS alike. The TS variation between two different reaction series expected from the simple Hammett and Brønsted coefficients, ρ X , ρ Z , β X and β Z , was incompatible with that predicted by the cross interaction constants, demonstrating again the unreliability of the simple parameters.