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Studies on organophosphorus compounds XXXII. A molecular mechanics study of the hydrolytic reaction of alkylphosphonates and alkylphosphonyl chlorides
Author(s) -
Li Shusen,
Liao Xiugao,
Yuan Chengye
Publication year - 1989
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.610020207
Subject(s) - chemistry , steric effects , alkyl , tetracoordinate , hydrolysis , alkaline hydrolysis , computational chemistry , steric factor , organic chemistry , medicinal chemistry , stereochemistry , computer graphics (images) , computer science , planar
The alkaline hydrolysis of several alkylphosphonates and alkylphosphonyl chlorides has been investigated by molecular mechanics calculations (MM2, 1985 version). The difference of the steric energies (Δ E ) between tetracoordinate substrate and pentacoordinate transition state of phosphorus compounds represents the activation energy (Δ E ≠ ) in hydrolysis. The change of Δ E for various alkyl groups relative to methyl group (ΔΔ E R ) is suggested as a measure of the steric effect of substituents. Thus the correlation analysis involving log k and ΔΔ E R of the branched alkyl group gives good results and it is reasonable to anticipate that analogous treatment using ΔΔ E R for the straight chain alkyl group is not satisfactory owing to the minor contribution of steric effect of the latter. However, the multiple regression analysis of log k with ΔΔ E R and Taft's σ* provides very good results. As shown by us, for the hydrolytic reactions studied, the proposed ΔΔ E R is much better than Taft's E s and Charton's ν, the commonly used well‐known steric parameters in the chemistry of carbon compounds.