Preparation Of Diborane Assignment Help | Preparation Of Diborane Homework Help

Preparation of diborane

Diborane cannot be synthesized directly from its elements as it has a positive enthalpy and a positive free energy of formation. ΔGf o. This may be attributed to very strong bonds in elemental boron and H2 which will have to be overcome before forming boron hydrides.
(1)    Diborane can be easily prepared in small quantities on a laboratory scale by the reaction iodine on sodium borohydride (Na BH4) in diglyme a high boiling ether. [(CH2 O CH2 CH2)2O].
2NaBH4 + I2  →  B2H6 + 2NaI + H2
                              (98% yield)

(2)    By the action of phosphoric acid on magnesium boride.
Mg3B2 + H3PO4 → (Mixture of boranes)  →  B2H6

(3)    It can be prepared by the reduction of boron halides by any one of the following methods:
(i)    Reduction of boron trifluoride with lithium hydride
8BF3 + 6LiH  →   6LiBF4 + B2H6

(ii)    Reduction of boron trichloride with lithium aluminum-hydride. This reaction gives quantitative yield

4BCI3 + 3LiAIH4 → 2B2H6 + 3LiCI + 3AICI3

(iii)    Reduction of boron trichloride vapours with molecular hydrogen by passing a silent electric discharge at low pressure

2BCI3 + 6H →  B2H6 + 6HCI

(iv)    It is quantitatively obtained by reaction of sodium borohydride with boron trifluoride

4BF3 + 3NaBH →  3NaBF4 + 2B2H6

For more help in Preparation of diborane click the button below to submit your homework assignment