==Physical properties== Tetrabromomethane has two polymorphs: crystalline II or β below 46.9 °C (320.0 K) and crystalline I or α above 46.9 °C. Monoclinic polymorph has space group C2/c with lattice constants: a = 20.9, b = 12.1, c = 21.2 (.10−1 nm), β = 110.5°. Bond energy of C-Br is 235 kJ.mol−1. Due to its symmetrically substituted te... Found on http://en.wikipedia.org/wiki/Tetrabromomethane