5-[(1R,2R,4R)-2-Methoxy-1,7,7-trimethylbicyclo[2.2.1] hept-2-yl]-1H-tetrazole

The title compound, C12H20N4O, undergoes a phase transition on cooling. The room-temperature structure is tetra-gonal (P4(3)2(1)2, Z' = 1), with the meth-oxy-bornyl group being extremely disordered. Below 213 K the structure is ortho-rhom-bic (P2(1)2(1)2(1), Z' = 2), with ordered mol-ecules. The two independent mol-ecules (A and B) have very similar conformations; significant differences only occur for the torsion angles about the C-bornyl-C-tetrazole bonds. The independent mol-ecules are approximately related by the pseudo-symmetry relation: x(B) = -1/4 + y(A), y(B) = 3/4 - x(A) and z(B) = 1/4 + z(A). In the crystal, mol-ecules are connected by N-HN hydrogen bonds between the tetra-zole groups, forming a pseudo-43 helix parallel to the c-axis direction. The crystal studied was a merohedral twin with a refined twin fraction value of 0.231 (2).