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Borane is an electron deficient compound. It has only six valence electrons, so the boron atom lacks an octet. Acquiring an octet is the driving force for the unusual bonding structure found in boron compounds. As an electron deficient compound, \( \mathrm{BH}_{3} \) is a strong electrophile, capable of adding to a double bond. This hydroboration of double bond is though to occur in one step, with the boron atom adding to the less highly substituted end of the double bond. In transition state, the boron atom withdraws electrons from the pi bond and the carbon at the other end of the double bond acquires a partial positive charge. This positive charge is more stable on the more highly substituted carbon atom. The second step is the oxidation of boron atom, removing it from carbon and replacing it with a hydroxyl group by using \( \mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{O} / \overline{1} \).

The simultaneous addition of boron and hydrogen to the double bond leads to a syn addition. Oxidation of
the trialkyl borane replaces boron with a hydroxyl group in the same stereochemical position. Thus, hydroboration of alkene is an example of stereospecific reaction, in which different stereoisomers of starting
compounds react to give different stereoisomers of the product.
\( Z \) is :
(A) Optically active 1 -alcohol
(B) Optically active 2 -alcohol
(C) Optically inactive 1 -alcohol
(D) Optically inactive 3 -alcohol
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