The addition of the compound containing a hydrogen-boron bond `H-B lt`(called a boron hydride) useful synthetic procedures. This addition, called hydrocarbon, is carried out by using the boron hydride.

Options

A. `BH_(3)`
B. `(BH_(3))_(2)`
C. `(BH_(3))_(3)`
D. `(BH_(3))_(4)`

Answer

B

Explanation

The reagent is `(BH_(3))_(2)` called diborane. It it is the dimer of the hypothetical `BH_(3)` (borane) but in the hydroboration reaction, it acts much as though it were `BH_(3)`. In fact, when diborane dissolves in tetrahydrofuran (one of the solvent used for hydroboration), `THF`, each `B_(2)H_(6)` molecule dissociates to produce two molecules of a complex between `BH_(3)` (called borane) and `THF`, i.e., the reagent exists as the monomer in the from of an acid-base complex with the solvent.

`BH_(3)` is Lewis acid beacuse the central `B` atom has only six electrons in its valence shell. It accepts `e^(-)` pair from the `O` atom of `THF`. Solutions containing the `THF:BH_(3)` complex can be obtained commercially.