Question

Diborane $\left( {{B_2}{H_6}} \right)$ reacts independently with ${O_2}$ and ${H_2}O$ to produce:
(A) $HB{O_2}$ and ${H_3}B{O_3}$
(B) ${H_3}B{O_3}$ and ${B_2}{O_3}$
(C) ${B_2}{O_3}$ and ${H_3}B{O_3}$
(D) ${B_2}{O_3}$ and $\left[ {B{H_4}} \right]$

Answer 1

Hint: Diborane on reaction with ${O_2}$ gives Boric anhydride whereas the diborane on reaction with ${H_2}O$ gives boric acid.It is a colorless, pyrophoric gas with a repulsively sweet odor. Synonyms include bromoethane, boron hydride, and diboron hexahydride.

Complete step by step answer:
Diborane reacts with oxygen to produce boron trioxide and water.
${B_2}{H_6} + 3{O_2} \to {B_2}{O_3} + 3{H_2}O$
This is an oxidation – reduction (redox) reaction:
$2{B^{ - III}} - 12{e^{ - 1}} \to 2{B^{III}}$ (Oxidation)
${60^\circ } + 12{e^{ - 1}} \to {60^{ - II}}$ (reduction)
${B_2}{H_6}$ is a reducing agent, ${O_2}$ is an oxidizing agent.
${B_2}{H_6}$ is known as diborane, ${O_2}$ is known as dioxygen, \[{B_2}{O_3}\] is known as boron trioxide and \[{H_2}O\] is known as water or oxidane.
Diborane reacts with water to form hydrogen and boric acid ${B_2}{H_6} + 6{H_2}O \to 2B{\left( {OH} \right)_3} + 6{H_2}$
Diborane reacts with water violently to form hydrogen and ${H_3}B{O_3}$. It mixes well with air and explosives mixtures are easily formed. At high concentrations, it will ignite spontaneously in moist air at room temperature. The main toxic effect of exposure to diborane is irritation of the respiratory airway, skin and eyes.
H for the reaction is - $466$KJ/mol which is also equal to - $16.82$KJ/gm.
Hence the correct answer is (C)

Note:
Diborane is commonly used for the reduction of carboxylic acid in the presence of esters, lactones, amides, halides and other functional groups. It rapidly reduces aldehyde, ketones and alkenes.
In diborane ${B_2}{H_6}$, only four terminal hydrogen atoms are replaceable. The two bridge H – atoms cannot be substituted. Hence, ${B_2}{\left( {C{H_3}} \right)_6}$ cannot be prepared from ${B_2}{H_6}$.