ACID-BASE REACTIONS BETWEEN AMINES AND CARBOXYLIC ACIDS IN HEXANE

The reactions of carboxylic acids (HX) and amine bases (B) were studied in the solvent hexane at 25° using the differential vapor pressure method and infrared spectroscopy. In general, the following equilibria are required to interpret the experimental results: 2HX rlhar2; (HX)2; B + HXrlhar2; (1/m)(BH+X−)m; and (1/m)(BH+- X−)m + HX rahar2;(1/n)(BH+HX2−)n. Detectable association of cyclohexyl- and n-hexylamines occuss at the 0.01 M level, while trichloroacetic and benzoic acids appear to be quantitatively dimerized at the same concentration. Some evidence for the BH+H2X3− species is given. The results in hexane are compared to a previous study by Bruckenstein and Saito1 in benzene as solvent. Compared to hexane, in benzene values of m and n are smaller, and trichloroacetic acid is far less dimerized, clearly indicating that benzene is capable of solvating the species participating in the acid-base and concurrent equilibria. © 1969, American Chemical Society. All rights reserved.