Question

Which of the following reactions can be used to prepare diborane? I) ${BF_3 + LiAlH_4 ->[ether]}$ II) ${BF_3 + NaH ->[450 k]}$ III) ${Na_2B_4O_7 + H_2O -> }$ IV) ${ NaBH_4 + I_2 ->}$

• A. I, II , III
• B. II , III only
• C. III , IV only
• D. I, II , IV

Answer 1

Answer: (D)

I, II , IV

Answer 2

Following reactions are used for the preparation of diborane: $(I) 4BF_3 + 3Li AlH_4 {->[\text{Diethyl ether}]} \underset{\text{Diborane}}{2B_2H_6} + 3LiF + 3AlF_3$ $(II) 2BF_3 + 6NaH {->[450\,K]} \underset{\text{Diborane}}{B_2H_6} + 6NaF$ (Industrial method) $(IV) 2NaBH_4 + I_2 {->[\text{DIGLYME}(MeOCH)2CH_2)O_2]}$ $\underset{\text{Diborane}}{B_2H_6} + \underset{\text{(Lab method)}}{2NaI + H_2} \uparrow$ Reaction $(III)$ is used for the preparation of boric acid. i.e., $Na_2B_4O_7 + 7H_2O {<=>} 2NaOH + \underset{\text{Boric acid}}{4H_3BO_3}$