A Study of the Monohydrate and Dihydrate Complexes of Perfluoropropionic Acid Using Chirped-Pulse Fourier Transform Microwave (CP-FTMW) Spectroscopy

This work reports the first known spectroscopic observation of the monohydrate and dihydrate complexes of perfluoropropionic acid (PFPA). The spectra have been observed using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer in the 7750 to 14250 MHz region. The structures of the species have been confirmed with the aid of ab initio quantum chemical calculations. Rotational constants A, B, and C have been determined and reported for both species along with centrifugal distortion constants ΔJ, ΔJK, ΔK, δJ, δK for H2O-PFPA and ΔJ, ΔJK, and δJ for (H2O)2-PFPA. Effects due to large amplitude motions were not observable in these experiments. Structures of the complexes have been determined using a combination of experimental second moment values and ab initio results. The complexation of the −OH of one or two water molecules has been found to occur in the plane of the carboxylic acid group forming a six- or eight-member ring.