Abstract: The reaction of the monomeric BH₃ with alkenes in ether media has been examined by using B3LYP, a hybrid density functional method, with 631G^* basis set. Calculations of various possible species involveDIn the hydroboration process, including the complexes of borane (BH₃) with dimethyl ether, ethylene, propene, 1-butene, trans-2-butene, cis-2-butene, 2-methylpropene, 2-methyl 2-butene and 2,3-dimethyl-2-butene as well as the reactants and transition states of the corresponding hydroboration have been performed. The zero point energies(ZPE) and thermal analyses were computed at the same level. Based on the calculations, the prior formation of a three center π-complex intermediate of BH₃ with the respective alkene is predicted and the overall reaction rate was determined. For the formation of the π-complex intermediates, two extreme pathways, i.e . the S_N1 and S_N2-like manner, have been compared, with the latter one more preferentially in terms of the activation barrier by 25²8 kJ/mol endothermically.

Key words: Hydroboration, Alkene, Ether, Catalysis, Density functional theory