Abstract
The crystal structure of the fentanyl base (C22H28N2O) is monoclinic, P21/n. The unit-cell dimensions at 293 K are a = 5.69263(10)Å, b = 25.1851(5)Å, c = 13.8608(3)Å, β = 104.2037(7)°. The R value is R = 0.0626 for 2208 reflections. The piperidine ring has a near-ideal chair conformation. In the packing, the intermolecular T-shaped π/π interactions were observed.
