Structural comparison of 1-bromo- and 1-fluoroestradiol with D-estradiol.

1-Bromoestra-1,3,5(10)-trien-3,17 beta-diol, C18H23BrO2, Mr = 351.3, orthorhombic, P2(1)2(1)2(1), a = 9.3864 (12), b = 12.927 (2), c = 12.948 (2) A, V = 1571.1 (4) A3, Z = 4, Dx = 1.484 Mg m-3, lambda(Mo K alpha) = 0.71069 A, mu = 259 mm-1, F(000) = 728, T = 298 K, R = 0.0514 for 2083 observed reflections. 1-Fluoroestra-1,3,5(10)-trien-3,17 beta-diol.0.5H2O, C18-H23FO2.0.5H2O, Mr = 299.4, orthorhombic, P2(1)2(1)2, a = 12.046 (4), b = 19.358 (5), c = 6.656 (2) A, V = 1552.1 (7) A3, Z = 4, Dx = 1.28 Mg m-3, lambda(Mo K alpha) = 0.71069 A, mu = 86 mm-1, F(000) = 644, T = 293 K, R = 0.0776 for 2781 observed reflections. Except for the carbon-halogen bond, bond angles and bond lengths of 1-bromoestradiol are within 7 e.s.d.'s of estradiol. Bond angles and bond lengths of 1-fluoroestradiol are within 11 and 7 e.s.d.'s of estradiol, respectively. The molecular conformations are nearly identical to that of estradiol. Like estradiol, 1-fluoroestradiol is present as a hemihydrate and extensive hydrogen bonding is observed. 1-Bromoestradiol is not hydrated and hydrogen bonding is limited to hydroxyl groups along the c axis.