Raman and synchrotron X‐ray diffraction studies of 4‐azidobenzoic acid under high pressures

Abstract

AbstractHere, we report the distinct behaviors of 4‐azidobenzoic acid (C7H5N3O2, 4‐ABA) in diamond anvil cells with the pressure up to ∼18 GPa at room temperature by in situ Raman scattering and synchrotron angle‐dispersive X‐ray diffraction (ADXRD) measurements. The analyses of Raman spectra revealed that 4‐ABA underwent a phase transition in the pressure range of 0.8–1.3 GPa and a conformational change at 6.3 GPa, which were supported by XRD results. The phase transition is attributed to the distortion of the benzene ring, and the change of hydrogen bonds results in the conformational change. Above 11.2 GPa, the (112) Bragg peak moved toward a low angle, indicating the increase of the interplanar distance of 4‐ABA. Upon compression to 18.0 GPa, 4‐ABA transformed into amorphous phase that the low amorphization pressure is helpful for nitrogen polymerization. This study provides an effective route for understanding the evolution of the azide group under high pressure, which is beneficial to studying the mechanism of forming polymeric nitrogen.