Stability and partial oligomerization of naphthalene under high pressure at room temperature

Highlights: • Naphthalene retained its crystal phase at around 20 GPa with a amorphous phase. • Naphthalene partially oligomerized above 15 GPa at room temperature. • The main reaction products could be divided into three types. • 1,2′-Binaphthyl is the most abundant product in three binaphthyl isomers. • The oligomerization would be promoted with decreasing intermolecular distance. The stability and pressure-induced chemical reactions of naphthalene were investigated at room temperature at pressures up to 23 GPa. In-situ X-ray diffraction (XRD) measurements indicated that naphthalene retained its crystal structure up to ∼20 GPa, whereas a solid amorphous phase was observed in the recovered samples. Based on microanalysis of the recovered samples using Gas Chromatograph Mass Spectrometer (GC/MS), naphthalene dimer and trimer isomers were observed at pressures exceeding 15 GPa. The dimers were classified as products of simple dimerization, naphthylation, and condensation, similar to the case of the pressure-induced dimerization of benzene, indicating a similar dimerization mechanism for naphthalene.