[reaction: see text] Solvolyses of methyl and ethyl chloroglyoxylates proceed about 10(6) times faster than the identical solvolyses of the corresponding chloroformates. The correlation parameters obtained from application of the extended Grunwald-Winstein equation are consistent with an addition-elimination (association-dissociation) mechanism over the full range of solvents, with the addition step being rate determining.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/jo050998m | DOI Listing |
J Am Chem Soc
February 2015
Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, Haus F, 81377 München, Germany.
Equilibria for the reactions of benzhydryl cations (Ar2CH(+)) with phosphines, tert-amines, pyridines, and related Lewis bases were determined photometrically in CH2Cl2 and CH3CN solution at 20 °C. The measured equilibrium constants can be expressed by the sum of two parameters, defined as the Lewis Acidity (LA) of the benzhydrylium ions and the Lewis basicity (LB) of the phosphines, pyridines, etc. Least-squares minimization of log K = LA + LB with the definition LA = 0 for (4-MeOC6H4)2CH(+) gave a Lewis acidity scale for 18 benzhydrylium ions covering 18 orders of magnitude in CH2Cl2 as well as Lewis basicities (with respect to C-centered Lewis acids) for 56 bases.
View Article and Find Full Text PDFCurr Org Chem
June 2012
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115-2862, USA.
The specific rates of solvolysis of chloromethyl phenyl sulfide [(phenylthio)methyl chloride] and its p-chloro-derivative have been determined at 0.0 °C in a wide range of hydroxylic solvents, including several containing a fluroalcohol. Treatment in terms of a two-term Grunwald-Winstein equation, incorporating terms based on solvent ionizing power (Y(Cl)) and solvent nucleophilicity (N(T)) suggest a mechanism similar to that for the solvolyses of tert-butyl chloride, involving in the rate-determining step a nucleophilic solvation of the incipient carbocation in an ionization process.
View Article and Find Full Text PDFInt J Mol Sci
February 2011
Department of Chemistry, Wesley College, 120 N. State Street, Dover, DE 19901, USA.
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.
View Article and Find Full Text PDFCurr Org Chem
June 2010
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115-2862, USA.
The original Grunwald-Winstein equation (1948) involved the development of a scale of solvent ionizing power (Y). Subsequent work has refined this scale and involved the development of scales of solvent nucleophilicity (N) and a term to correct for deviations when aromatic rings are present, governed by the aromatic ring parameter (I). These three scales, and the sensitivities towards each, can be related to specific rates of solvolysis through linear free energy relationships (LFERs).
View Article and Find Full Text PDFChemistry
July 2010
Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany.
First-order rate constants k(w) for the reactions of a series of donor-substituted triphenylmethylium (tritylium) ions with water in aqueous acetonitrile have been determined photometrically at 20 degrees C using stopped-flow and laser-flash techniques. The rate constants follow the linear free energy relationship log k(20 degrees C)=s(N+E). The reactivities k(w) of the methyl- and methoxy-substituted tritylium ions towards water correlate linearly with the corresponding pK(R(+) ) values with a Leffler-Hammond coefficient alpha=deltaDeltaG(++)/deltaDeltaG(0) of 0.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!