Abstract
The influence of carbon-carbon multiple bonds on the solvolyses of 3-chloro-3-methylbutyne (1), 2-chloro-2-phenylpropane (2), 2-bromo-2-methyl-1-phenylpropane (3), 4-chloro-4-methyl-2-pentyne (4) and 2-chloro-2-methylbutane (5) is critically evaluated through the extended Grunwald-Winstein equation. Substrates 1, 3 and 5 lead to correlations with unexpected negative sensitivity, h, to changes in the aromatic ring parameter, I. It is claimed that I is not a pure parameter, reflecting also some solvent nucleophilicity, NOTs, character. In substrates 2 and 4 the possibility of rearside solvation is reduced due to steric hindrance and/or cation stabilization and the best found correlations involve only the solvent ionizing power, Y, and I.
Highlights
The study of solvent effects in reactivity has been one of the cornerstones of physical organic chemistry, and still constitutes these days one of the most fascinating scientific challenges
Kevill et al have shown that the introduction of a new solvent parameter, which they named as “aromatic ring parameter”, I, based on the solvolyses of (p-methoxybenzyl)dimethylsulfonium ion and 1adamantyldimethylsulfonium ion (as stated by Kevill and co-workers, the I scale is based on differences in the nature of the variations of rate constants of solvolysis of the p-dimethylsulfonium ion and of the 1-adamantyldimethylsulfonium ion as the solvent composition is altered: I = log (k/k0)p-MeOC6H4CH2SMe2 -1.3 log (k/k0)1-AdS+Me2, where k0 is the rate of solvolysis in 80% ethanol [15]), corrected for the dispersion observed in Grunwald-Winstein plots for substrates with aromatic rings which could enter into conjugation with the developing positive charge at the α- carbon [15, 23]
In this paper we report a comparative study of the influence of carbon-carbon multiple bonds on the solvolyses of 5 tertiary alkyl halides by using the Grunwald-Winstein extended equation
Summary
The study of solvent effects in reactivity has been one of the cornerstones of physical organic chemistry, and still constitutes these days one of the most fascinating scientific challenges. Differences in the nature of the variations of rate constants of solvolysis of the p- (methoxybenzyl)dimethylsulfonium ion and of the 1-adamantyldimethylsulfonium ion (no aromatic ring) as the solvent composition is altered: I = log (k/k0)p-MeOC6H4CH2SMe2 -1.3 log (k/k0)1-AdS+Me2, where k0 is the rate of solvolysis in 80% ethanol [15]), corrected for the dispersion observed in Grunwald-Winstein plots for substrates with aromatic rings which could enter into conjugation with the developing positive charge at the α- carbon [15, 23] These authors have proposed the inclusion of this new term in eq (2) to comprise those situations for which there was cationic charge delocalization by resonance: log k = mY + lN + hI + c (3). [20] for which there is no possibility of charge delocalization, namely 2-chloro-2-methylbutane (5)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
