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Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent
Department of Chemistry, Wesley College, 120 N. State Street, Dover, DE 19901, USA
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115, USA
* Authors to whom correspondence should be addressed.
Received: 6 January 2011; in revised form: 30 January 2011 / Accepted: 9 February 2011 / Published: 15 February 2011
Abstract: The specific rates of solvolysis of neopentyl chloroformate (1) have been determined in 21 pure and binary solvents at 45.0 °C. In most solvents the values are essentially identical to those for ethyl and n-propyl chloroformates. However, in aqueous-1,1,1,3,3,3-hexafluoro-2-propanol mixtures (HFIP) rich in fluoroalcohol, 1 solvolyses appreciably faster than the other two substrates. Linear free energy relationship (LFER) comparison of the specific rates of solvolysis of 1 with those for phenyl chloroformate and those for n-propyl chloroformate are helpful in the mechanistic considerations, as is also the treatment in terms of the Extended Grunwald-Winstein equation. It is proposed that the faster reaction for 1 in HFIP rich solvents is due to the influence of a 1,2-methyl shift, leading to a tertiary alkyl cation, outweighing the only weak nucleophilic solvation of the cation possible in these low nucleophilicity solvents.
Keywords: solvolysis; 1,2-methyl shift; LFER; addition-elimination; Grunwald-Winstein equations; ionization; neopentyl chloroformate
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D’Souza, M.J.; Carter, S.E.; Kevill, D.N. Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent. Int. J. Mol. Sci. 2011, 12, 1161-1174.
D’Souza MJ, Carter SE, Kevill DN. Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent. International Journal of Molecular Sciences. 2011; 12(2):1161-1174.
D’Souza, Malcolm J.; Carter, Shannon E.; Kevill, Dennis N. 2011. "Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent." Int. J. Mol. Sci. 12, no. 2: 1161-1174.