SOLID-STATE POLYMORPHISM IN 4-CYANO-4'-NORMAL-PROPYLBIPHENYL AND X-RAY STRUCTURE DETERMINATION OF THE HIGHER MELTING MODIFICATION

DSC and thermomicroscopic analysis of 4-cyano-4 prime -n-propylbiphenyl (CB 3) revealed solid crystalline polymorphism. Thus the compound exhibits two solid phases subsequent to appropriate thermal treatment. The melting points are K//I: 338. 4 (5) K and K//I//I: 326. 3(3) K. The enthalpies of fusion for K//I and K//I//I are 19. 9(5) kJ/mol and 16. 7(7) kJ/mol, respectively. The compound also possesses a monotropic nematic phase, its clearing point being 303. 3(2) K and DELTA H//N// minus //I equals 0. 3(2) kJ/mol. The crystals of the higher melting modification are monoclinic, with a equals 6. 259 (3) A, b equals 19. 1216 (9) A, c equals 11. 0473 (5) A and beta equals 103. 39 (2) degree . The space group is P2//1/c. For 1014 nonzero reflections, R equals 0. 051, R//w equals 0. 042. The dihedral angle between the phenyl rings was found to be 42. 8 degree .