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Réactivité des bromures de benzyle substitués envers le thiophénate et le méthylate de lithium
Author(s) -
Klopman G.,
Hudson R. F.
Publication year - 1961
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19610440712
Subject(s) - chemistry , substituent , lithium (medication) , medicinal chemistry , nucleophile , lithium bromide , reactivity (psychology) , bromide , covalent bond , methoxide , ionic bonding , methanol , ion , organic chemistry , catalysis , physics , alternative medicine , pathology , thermodynamics , endocrinology , medicine , heat exchanger
The rate of reaction of several p‐substituted benzyl bromides with lithium thiophenoxide (k phs ) and lithium methoxide (K MeO ) in methanol have been measured polarographically. In both series of reactions, the reactivity increases on introduction of electron releasing and electron attracting substituents. This is explained by a change in the transition state structure from an essentially ionic form, to a more covalent form stabilised by conjugation between the benzene ring and the pseudo‐π orbitals forming the reaction coordinates. The ratio k Phs /k Meo increases with the H AMMETT σ value for the substituent in the benzyl bromide, showing that the selectivity of the nucleophile increases with the extent of covalent bond formation in the transition state.