Crystallization of a Racemate Affords a P21 Chiral Crystal Structure: Asymmetric Unit of Two Opposite Handed Molecules Simulates Achiral P21/n Packing via Pseudosymmetry

A racemic mixture consisting of a secondary ammonium salt (±)-(1RS,3SR,4RS)-1-phenyl-cis-3,4-n-butano-5,6-dihydro-1H-2,5-benzoxazocine hydrochloride (1) crystallized as a “false conglomerate” of crystals in the monoclinic system, Sohncke space group P21 with two molecules of opposite handedness in the asymmetric unit and at 295(2) K: a = 10.224(2) A, b = 13.969(2) A, c = 12.724(2) A, β = 98.996(2)°, V = 1794.9(5) A3, Z = 4, and Z′ = 2. The cis-3,4-n-butano-5,6-dihydro-1H-2,5-benzoxazocine fused-ring skeletons are approximately enantiotopic and exhibit pseudoinversion and pseudo-n-glide relationships. These noncrystallographic symmetries enable space filling in the chiral crystal structure to resemble that of a higher order achiral P21/n apparent space group (Z = 4, Z′ = 1). The secondary ammonium salt molecules crystallize in patterns influenced by a complex blend of N−H···Cl, C−H···Cl, C−H···O, and C−H···Ar interactions that seem to be responsible for different conformational twists of the phenyl rings i...