An X-ray analysis of the structure of chrysene

Chrysene crystallizes in the monoclinic system. By means of rotation, oscillation, and moving film photographs the following crystal data have been obtained:— a = 8·34 A, b = 6·18 A, c = 25·0 A, β = 115·8°. All the planes (hkl) are halved when h + k + l is odd and in addition all the (h0l) planes are halved. There are two space groups available, C62h (I2/c) and C4s (Ic). In what follows it will be shown that the former space group is the more probable. The measured density is 1·27 (at room temperature) giving 4 molecules of C18 H12 per unit cell. Molecular volume = 290 (A)3.