A new crystalline (alpha) form of 1,4-dicyanobenzene

1,4-Dicyanobenzene is dimorphous, crystallizing in both triclinic (beta) and monoclinic (alpha) form. The triclinic form is transformed into the monoclinic above 430 K. Single crystals of the latter have been obtained and its structure determined at room temperature. The cell dimensions are a=3.868(1), b=7.080(1), c=12.127(2) Angstrom, beta=97.21(3)degrees, V=329.48(11) Angstrom(3), space group P2(1)/c; Z=2. The structure was solved by direct methods and 54 parameters refined on F to R=0.050, wR=0.061 and S=1.29 for 535 observed reflections (F>4 sigma((f)) measured in the range 4 less than or equal to 2 theta less than or equal to 60 (Mo K alpha radiation). The details of the alpha-form crystal structure are discussed and compared with the beta-form described in the literature.