FT-IR Solution Spectra of Propyl Sulfide,Propyl Sulfoxide,and Propyl Sulfone

Abstract

FT-IR spectra were obtained of 0.5% volumetric solutions of propyl sulfide, propyl sulfoxide, and propyl sulfone in hexane, CCl₄, CS₂, and CHCl₃ to assist in the assignment of FT-IR-PAS spectra of propyl sulfoxide sorbed within the structure of several peats and onto cellulose. The C-H stretching bands of all three compounds showed a 10-fold larger solvent sensitivity than did analogous aliphatic bands in a comparable series of n-alkanes in solution. The S=O stretching bands of alkyl sulfoxides are known to be quite sensitive to solvent environments because of donor-acceptor interactions involving the oxygen of the sulfoxide group and the slightly acidic protons of generalized organic acids; the expected decreases in frequency were seen with propyl sulfoxide and acidic solvents like chloroform. The frequencies of asymmetric and symmetric stretching vibrations of the -SO₂ group of propyl sulfone both exhibit smaller decreases in Old, than does the sulfoxide S=O stretching vibration.