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 exam ined 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, ethy lene, propene, 1-butene, trans-2-butene, cis-2-butene, 2-methylpropene, 2-m ethyl-2-butene and 2,3-dimethyl-2-butene as well as the reactants and trans ition states of the corresponding hydroboration have been performed. The ze ro-point energies(ZPE) and thermal analyses were computed at the same level , Based on the calculations, the prior formation of a three-center pi compl ex intermediate of BH3 with the respective alkene is predicted and the over all reaction rate was determined. For the formation of the pi complex inter mediates, two extreme pathways, i.e. the S(N)1 and S(N)2-like manner, have been compared, with the latter one more preferentially in terms of the acti vation barrier by 25 similar to 28 kJ/mol endothermically.