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Published October 20, 1993 | public
Journal Article

Conformational changes of butanedioic acid as a function of pH as determined from changes in vicinal proton-proton NMR couplings

Abstract

Vicinal proton-proton NMR couplings have been used to estimate the changes in conformational equilibria for butanedioic acid in the progression of its diprotic to monoprotic to di-ionized forms as a function of pH, concentration, and nature of the counterion. The results support earlier conclusions that the K_1/K_2 ratio for butanedioic acid is little, if at all, affected by internal hydrogen bonding in the monoanion. Perhaps surprisingly, the conformational preferences are weak, despite the possibility of steric hindrance and strong stabilizations by hydrogen-bonding, induction, and/or electrostatic effects.

Additional Information

© 1993 American Chemical Society. Received September 1, 1992. Publication Date: October 1993. This research was supported by the Caltech Consortium in Chemistry and Chemical Engineering; founding members: E. I. du Pont de Nemours and Company, Inc., Eastman Kodak Company, and Minnesota Mining and Manufacturing Company. Additional support was provided by the Caltech Summer Undergraduate Research Program (SURF). We are indebted to Dominic McGrath and David Wheeler for their assistance during the initial phases of the investigation, to Dr. Jane Raymond for her help throughout, and very much to Professor Julius Rebek, Jr., of the Massachusetts Institute of Technology for a number of incisive suggestions regarding possible interpretations of the results.

Additional details

Created:
August 20, 2023
Modified:
October 24, 2023