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.