Investigation of the molecular and crystalline structure of 2,4,6-triazido-3-chloro-5-trifluoromethylpyridine and rotation barrier of the γ-azidogroup around a C-N bond

Abstract

The molecular and crystalline structure of 2,4,6-triazido-3-chloro-5-trifluoromethylpyridine has been investigated by X-ray diffraction at temperatures of 200 and 293 K. The triazide molecule is nonplanar, and the γ-azidogroup significantly deviates from the aromatic ring plane. Nonempirical quantum-chemical calculations of the internal rotation barrier of the γ-azidogroup around the C-N bond have been performed in the B3LYP/6-311G** approximation. It is shown that the minimum of the total energy of this system corresponds to the dihedral angle between the γ-azidogroup and pyridine cycle planes (∼34.5°), whereas the structures with the γ-azidogroup, oriented in the pyridine cycle plane or perpendicularly to it, are characterized by very low barriers: ∼0.26 and 1.74 kcal mol⁻¹, respectively.