Infrared and Raman Spectroscopy Studies of Light and Heavy Trifluoroacetic Acids

Abstract

An infrared and Raman spectroscopic study of light and heavy trifluoroacetic acids shows that their vapors at room temperature are composed of a mixture of monomeric and associated molecules. The principal bands corresponding to vibrations of the COOH and COOD groups have been identified for both the monomeric and the associated molecules by means of a comparative study of the two acids (a) in the vapor state at different pressures, (b) in CCl4 solutions at various concentrations, and (c) in the liquid state. The monomeric carbonyl frequencies, influenced by the presence of the perfluoromethyl group, are the highest yet reported in the literature; this is true not only for CF3COOH (1826 cm−1, vapor), CF3COOD (1823 cm−1, vapor), but also for the ethyl ester, CF3COOC2H5 (1802 cm−1, vapor), the sodium salt, CF3COONa (1687 cm−1, solid), and the anhydride (CF3COO)2O (1884 cm−1 and 1818 cm−1, vapor). On the basis of a comparative study of the spectra of all these compounds, as well as of other perfluoromethyl compound spectra reported in the literature, the C–F stretching vibrations for the two acids have been assigned to the strong infrared absorptions at 1244 cm−1 and 1185 cm−1. The corresponding Raman bands are very weak.

Growth and characterization of the nonlinear optical crystal: L‐arginine trifluoroacetate

“…Vibrational bands at 1330 cm -1 in IR spectrum and 1333 cm -1 in Raman spectrum are assigned to CH 2 wagging. It should be noted that the next strong band at 1196 cm -1 in IR spectrum is assigned to C-F stretching, which is the characteristic vibration peak of CF 3 group [9][10][11][12]. The corresponding band in Raman spectrum appears at 1213 cm -1 .…”

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

“…Compounds like pyrazine are the most important products among the volatiles that were identified. A strong absorption band was observed at 1150 cm -1 for the electrospun samples heated until 300 ºC (figure 6), corresponding to the C -F stretching band due to the -NH3 + CF3COO -salts previously formed during polymer dissolution in a TFA/DCM mixture, and proves the existence of such residues, probably located in the side groups of the electrospun polymeric chains [26,27]. The absorption band at 1150 cm -1 was also observed for the chitosan samples submitted to ethanol neutralization and cross-linking with GA (data not shown).…”

Effect of trifluoroacetic acid on the properties of polyvinyl alcohol and polyvinyl alcohol–cellulose composites

“…1c); namely, C@O stretching at 1784 cm À1 , and absorption bands at 1225 and 1165 cm À1 for the asymmetric and symmetric CF 3 stretching modes, respectively. Specifically, the C@O stretching mode of TFA is very sensitive to the molecular environment [44,45]. In this case, the value of the wavenumber of this band for P100 could be related to the interaction of TFA molecules with the hydroxyl groups of PVA through hydrogen bonding (as proton donors).…”