Two polymorphs, with Z' = 1 and 2, of 2-amino-4-chloro-6-morpholino-pyrimidine in P2_1/c, and 2-amino-4-chloro-6-piperidinopyrimidine, which is isomorphous and almost isostructural with the Z' = 2 polymorph

Crystallization of 2-amino-4-chloro-6-morpholinopyrimidine, C8H11ClN4O, (I), yields two polymorphs, both with space group P2(1)/c, having Z' = 1 (from diethyl ether solution) and Z' = 2 (from dichloromethane solution), denoted (Ia) and (Ib), respectively. In polymorph (Ia), the molecules are linked by an N-H...O and an N-H...N hydrogen bond into sheets built from alternating R-2(2) (8) and R-6(6) (40) rings. In polymorph (Ib), one molecule acts as a triple acceptor of hydrogen bonds and the other acts as a single acceptor; one N-H...O and three N-H...N hydrogen bonds link the molecules in a complex chain containing two types of R-2(2) (8) and one type of R-4(4) (18) ring. 2-Amino-4-chloro-6-piperidinopyrimidine, C9H13ClN4, (II), which is isomorphous with polymorph (Ib), also has Z' = 2 in P2(1)/c, and the molecules are linked by three N-H...N hydrogen bonds into a centrosymmetric four-molecule aggregate containing three R-2(2) (8) rings.