INVESTIGADORES
VERA Domingo Mariano Adolfo
artículos
Título:
Theoretical Study of Elecron Transfer to Neopentyl Chloride and Phenyl-Substituted Derivatives
Autor/es:
D. MARIANO A. VERA, ADRIANA B. PIERINI
Revista:
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
Editorial:
Wiley Interscience
Referencias:
Año: 2002 vol. 15 p. 894 - 902
ISSN:
0894-3230
Resumen:
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ABSTRACT: Aliphatic halides such as
neopentyl, bicycloalkyl and polycycloalkyl halides can be substituted
bymechanisms that involve electron transfer (ET) steps. The
homogeneous or heterogeneous ET to these compounds follows a
concerted dissociative pathway, that is, the Chalogen bond cleaves
as the electron is being transferred. The ET to alkyl halides
substituted by p-electron acceptors, on the other hand, may follow a
stepwise mechanism with radical anions as intermediates. Both
mechanistic pathways are analyzed on the basis of AM1, B3LYP and MP2
calculations for neopentyl chloride (6) and its phenyl- and
benzyl-substituted derivatives 1-chloro-2-methyl-2-phenylpropane
(neophyl chloride, 7) and 1-chloro-2,2-dimethyl-3-phenylpropane (8).
The solvent effect wasevaluated with Tomasis continuum polarized
model. While relatively stable p radical anions appear as
intermediates on the AM1 potential surfaces of 7 and 8, B3LYP and MP2
favor a concerted dissociative pathway for these compounds. Based on
the B3LYP and MP2 results, it can be concluded that the driving force
for the dissociative ET to the three compounds depends mainly on
their CC1 bond dissociation. The strength of the CC1 bond is
similar for 6 and 8 and lower for 7. The difference in the CC1
bond strength of 7 and 8 is ascribed to differences in the
stabilizing effect of the phenyl substituent, through a bridge of
variable length, and also to the stability of the radical formed in
the cleavage. The theoretical results obtained are of help in the
interpretation of the relative experimental reactivity previously
obtained for the family. Copyright 2002 John Wiley & Sons,
Ltd.
KEYWORDS: concerted-dissociative
electron transfer; stepwise electron transfer; neopentyl halides and
stabilized derivatives; radical anions; B3LYP; MP2; AM1