Solvent effects on infrared spectra of progesterone in CHCl3/cyclo-C6H12 binary solvent systems

The infrared spectroscopy studies of the C3 and C20 carbonyl stretching vibrations (υ(CO)) of progesterone in CHCl3/cyclo-C6H12 binary solvent systems were undertaken to investigate the solute–solvent interactions. With the mole fraction of CHC13 in the binary solvent mixtures increase, three types of C3 and C20 carbonyl stretching vibration band of progesterone are observed, respectively. The assignments of υ(CO) of progesterone are discussed in detail. In the CHCl3-rich binary solvent systems or pure CHCl3 solvent, two kinds of solute–solvent hydrogen bonding interactions coexist for C20 CO. Comparisons are drawn for the solvent sensitivities of υ(CO) for acetophenone and 5α-androstan-3,17-dione, respectively.