Ah&act--Infrared
and Raman spectra of liquid and solid (chloromethyl)thiirane (3chloropropylene sulfide), along with the infrared and microwave spectra of the vapor, have been recorded. The vibrational spectra are consistent with the existence of at least two conformations. Unlike the situation found for related molecules, the gauche-2 conformation of (chloromethyl)thiirane appears to be the most stable in all three phases. Variable temperature studies of the Raman spectra of the liquid allowed an enthalpy difference of 0.44 kcal mol-' between the gauche-l and gauche-2 conformers to be calculated. The temperature dependence of certain Raman lines and the results of solution studies (infrared and Raman) suggest that a small amount of a third conformer (ci.r) might exist in the fluid phases. These experimental conclusions are supported by semi-empirical calculations (using the AM1 Hamiltonian) which suggest that all three conformers should be stable in the order: gauche-2>gauche-l > cis. In the microwave spectrum, the observed conformer has been experimentally determined to be the gauche-l form with the rotational constants (in MHZ): A =75%.5&t, B= 1706.588, and C= 1476.982. The nuclear quadrupole constant t]x.. has been determined to be -40.01 f0.38 MHz The structure and conformations of (chloromethyl)thiirane are compared with related three-membered ring compounds.