Trimethylborane (TMB) is a toxic, pyrophoric gas with the formula B(CH₃)₃ (which can also be written as Me₃B, with Me representing methyl). Its melting point is -161.5 °C and its boiling point is -20.2 °C. Vapour pressure is given by log P = 6.1385+1.75 log T - 1393.3/T - 0.007735 T. T is temperature in Kelvin. CAS number is 593-90-8. Molecular weight is 55.914. The heat of vapourisation is 25.6 kJ/mol.