The consistent valence-force field of alkanethiols (AlkSH), dialkyl sulfides (AlkSAlk"), and alkanedithiols (HSRSH, R is alkylene) was determined for the first time by the solution of an inverse spectral problem. The vibrational spectra of 40 linear and branched molecules AlkSH, RSR", and HSRSH were calculated. Their thermodynamic functions (enthalpy, entropy, thermal capacity, and free Gibbs energy) were determined by methods of statistical mechanics in the 298—1500 Ê temperature interval. Within the framework of the additive-group approach, the quantitative relationships “structure—property” were considered for the thermodynamic functions of AlkSH, AlkSAlk", and HSRSH, and the parameters of the relationships were calculated. The results of calculations and experimental data were compared.