X-Ray crystallographic analysis of N-(1-naphthyl)-2(1H)-pyrimidinethione revealed that the space group was tetragonal and chiral P4(3). The rate of racemization due to the C-N bond rotation was considerably influenced by the solvent properties. A nonpolar solvent lowers the ΔG(‡)value by about 3.0 kcal mol(-1) relative to the value in a polar or a protic solvent. The crystallization of racemic axially chiral pyrimidinethione at high temperature led to the chiral breaking of symmetry up to 91% ee.