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Theoretical studies on the transition‐state imbalance in malononitrile anion‐forming reactions in the gas phase and in water
Author(s) -
Lee Ikchoon,
Kim Chang Kon,
Lee BonSu,
Kim Chan Kyung,
Lee Hai Whang,
Han In Suk
Publication year - 1997
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/(sici)1099-1395(199712)10:12<908::aid-poc961>3.0.co;2-c
Subject(s) - chemistry , gas phase , nucleophile , solvation , polarization (electrochemistry) , amine gas treating , ion , phase transition , transition state , phase (matter) , dispersion (optics) , computational chemistry , thermodynamics , catalysis , organic chemistry , quantum mechanics , physics
Abstract Semiempirical MO theoretical studies were carried out on the nucleophilic addition of phenoxide nucleophiles to 1,1‐dicyano‐2‐arylethenes in the gas phase and in water using the AM1 method and the Cramer–Truhlar solvation model SM2.1. The gas‐phase α n and β n values are 0·81 and 0·65, respectively, leading to the positive imbalance of I =0·16; the electric polarization and dispersion interactions of water incorporated in the SM2.1 model reduce both the α n and β n values to 0·61 and 0·36, giving I =0·25. The two Brønsted coefficients obtained theoretically in water agree satisfactorily with the experimental values (α n corr =0·55 and β n =0·35) obtained with amine bases. The small imbalance found both theoretically ( I =0·25) and experimentally ( I ≈0·20) can be ascribed to (i) a near‐zero distance factor, Δ d = d p − d TS ≈0 and (ii) the small extent of negative charge localization by strucutral reorganization in the transition state. © 1997 John Wiley & Sons, Ltd.