ISSN:
0894-3230
Keywords:
AM1-SM2.1
;
transition-state imbalance
;
benzylidenemalonotriles
;
nucleophilic additions
;
Brønsted coefficients
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
---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 αn and βn 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 αn and βn 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 (αncorr=0·55 and βn=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, Δd=dp-dTS≈0 and (ii) the small extent of negative charge localization by strucutral reorganization in the transition state. © 1997 John Wiley & Sons, Ltd.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
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