Temperature-dependent gas-phase H-1 NMR spectra of seven thiocarbonyl-substituted N,N-dimethylthioamides (YCSN(CH3)(2)) obtained at 300 MHz are consistent with the following free activation energies Delta G(298)(double dagger) (kcal mol(-1)) : Y = H, 22.5 (0.1); CH3, 18.0 (0.1); F, 18.3 (0.1); Cl, 16.9 (0.2); CS, 17.2 (0.1); CH2CH3, 17.6 (0.1); CH(CH3)(2), 16.3 (0.1). The results are compared to condensed-phase values and to the corresponding gas-phase oxoamides.