Acid-induced 13C Nuclear Magnetic Resonance Chemical Shift Changes of Ether and Ester Carbon Atoms
13C N.m.r. chemical shifts of ehters dissolved in tetrachloromethane are displaced on addition of trifluoroacetic acid.The displacements result from independent interactions of the acid with the substrate oxygen atoms and alkyl residues.The structure-dependent and stereoselective shift changes are useful for signal assignments, structure determination, conformational analysis, assessment of the distribution of rapidly interconverting conformers of esters, and estimation of the relative basicity of ethers.
Begtrup, Mikael
p. 1609 - 1618
(2007/10/02)
Oxidatively Assisted Nucleophilic Substitution/Elimination of Alkyl Iodides in Alcoholic Media. A Further Study
Oxidation of a series of alkyl halides with alcoholic 3-chloroperoxybenzoic acid afforded the results outlined in Charts I-III and Tables I-III.The reaction was found to be a powerful and convenient method for effecting nucleophilic substitution in a variety of systems, including the highly inert 1- and 7-bicycloheptyl systems.Qualitatively, the number of molar equivalents of oxidant required varied inversely with the expected ease of substitution for a given system.A mechanism is suggested whereby the iodide is oxidized stepwise to a species RIOn in which n is an integer sufficiently large that the system in question will undergo nucleophilic substitution or elimination.Reaction in the presence of added chloride or bromide ion usually resulted in a facilitation of reaction rate and a decrease in the number of molar equivalents of oxidant required; the principal product under these conditions was usually the corresponding chloride or bromide.
Davidson, Robert I.,Kropp, Paul J.
p. 1904 - 1909
(2007/10/02)
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