(E)-9-(But-2-en-1-yl)-6-chloro-9H-purine

The asymmetric unit of the title compound, C9H9ClN4, contains two molecules. In the crystal, the molecules are ordered in a chain- like fashion along the a axis, and form layers offset relative to the C plane by approximately 30 degrees. This ordering does not, however, appear to be directed by classical hydrogen bonding. The allylic side chains of both independent molecules are disordered, with occupancies of 0.870 (4) and 0.934 (3) for the major components. The disorder components represent two possible spatial orientations of the atoms around the C=C double bond.