Réactivité des bromures de benzyle substitués envers le thiophénate et le méthylate de lithium
✍ Scribed by G. Klopman; R. F. Hudson
- Publisher
- John Wiley and Sons
- Year
- 1961
- Tongue
- German
- Weight
- 441 KB
- Volume
- 44
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
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 HAMMETT 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.
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