SYNTHESIS, THEORETICAL CONFORMATIONAL STUDY AND X-RAY STRUCTURES OF 2,2'-DIMETHYL-4,4'-BIPYRIMIDINE AND 6,6'-DIMETHYL-2,2'-BIPYRAZINE

The synthesis of 2,2'-dimethyl-4,4'-bipyrimidine (bpm) and 6,6'-dimeth yl-2,2'-bipyrazine (bpz) is described. In these compounds the s-trans molecular conformation has been observed and could be interpreted in t erms of weak C-H...N interactions. The crystal stacking in the two com pounds is formed by parallel molecular planes which are 3.46 angstrom apart. A semi-empirical calculation shows that, irrespective of the me dium, the molecules conserve this preferential conformation.