The pure rotational spectra of cyclopropanecarboxylic acid (CPCA) and the dimer of CPCA with formic acid (CPCA-FA) were studied using a Flygare-Balle type pulsed-beam Fourier transform microwave spectrometer. Rotational constants and centrifugal distortion constants were determined for the first time for the higher energy conformer of CPCA as well as the singly substituted <sup>13</sup>C isotopomers of the most stable conformer, and the parent, four unique singly substituted <sup>13</sup>C, and one singly deuterated isotopomers of CPCA-FA. The substituting structure and the best fit structure were derived from the spectroscopic parameters. The difference in the monomer conformation is primarily due to the acidic OH bond moving from the anti-syn to the syn-syn conformation. Splittings due to a possible concerted proton tunneling motion were not observed for CPCA-FA. The experimental values are compared to those obtained from quantum mechanical calculations.

Microwave spectroscopy of cyclopropanecarboxylic acid and the cyclopropanecarboxylic acid-formic acid dimer

251st National Meeting (2016)

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