Two crystallographic forms and the absolute structure of 5α,14α‐androstane

5α,14α‐Androstane (C19H32) crystallizes in two different polymorphic forms in the same vapor diffusion experiment. The major form (Form I) crystallizes as thin plates in the space group P21, with Z = 4. These plates are twinned along a long c axis of length 43 Å and readily suffer from radiation damage when diffracted. The minor form (Form II) crystallizes as fine needles in the space group P212121, Z = 3. In the minor form, 5α,14α‐androstane cocrystallizes with 5α,14α‐androstan‐17‐one, an oxidation product of 5α,14α‐androstane. The presence of 5α,14α‐androstan‐17‐one in the minor form of the crystals was confirmed by HR‐MS. Form II can be crystallized as a pure form without the ketone impurity using a different solvent system. High level density functional theory (DFT) lattice free energy calculations were performed and show that both pure forms are isoergic within the estimated error of the calculations. 5α,14α‐Androstane crystallizes in two different crystallographic forms, which have been calculated to be isoergic in terms of their free energy. The presence of the ketone impurity 5α,14α‐androstan‐17‐one was detected in Form II crystals grown from diethyl ether, while the absolute stereochemistry has been determined in pure Form II crystals.