A Theoretical Simulation of Hydroboration of Alkenes with BH3 in Ether Media

The reaction of the monomeric BH3 with alkenes in ether media has been examined by using B3LYP, a hybrid density functional method, with 6-31G* basis set. Calculations of various possible species involved in 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 SN1 and SN2-like manner, have been compared, with the latter one more preferentially in terms of the activation barrier by 25 [similar to] 28 kJ/mol endothermically.