Gas phase acidities of aliphatic carboxylic acids, based on measurements of proton transfer equilibria

1 April 1989

journal article
Published by Canadian Science Publishing in Canadian Journal of Chemistry

Vol. 67 (4) , 611-618
https://doi.org/10.1139/v89-092

Abstract

Measurements of the gas phase proton transfer equilibrium [1]: AH + B⁻ = A⁻ + BH with a pulsed electron high pressure mass spectrometer (PHPMS) lead to [Formula: see text] and [Formula: see text] data. These relative acidities are converted to the absolute acidities [2]: AH = A⁻ + H⁺bycalibration of the relative [Formula: see text] and [Formula: see text] scale to the known values for [Formula: see text] and [Formula: see text] of a reference compound(HCl). Earlier determinations that included 16 aliphatic AH are extended in the present work and provide data for 47 aliphatic carboxylic acids. These include halogen, OH, CH₃O, C₂H₅O, PhO, and NH₂ substituted acetic acids, and halogen substituted, unsaturated, and cyclic RCO₂H of higher carbon number. The effects of the various substituents on the gas phase acidity are briefly examined. Keywords: acidities in gas phase, proton transfer equilibria, ion-molecule equilibria, mass spectrometry.

Keywords

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