Borohydride

The anion BH4- and its salts are referred to as borohydrides. These compounds are used as reducing agents in organic synthesis. Sodium borohydride and lithium borohydride are the most important borohydrides. One of the main uses of sodium borohydride is in the reduction of sulphur dioxide to give sodium dithionite, which is employed to bleach wood pulp.

Sodium borohydride is frequently used in fine chemical and pharmaceutical industries, especially in the reduction of aldehydes and ketones in the production of atropine, chloramphenicol, scopolamine and vitamin A. The widespread use of borohydrides for the reduction of aldehydes and ketones is attributed to its ready availability, mild reaction conditions, ease of work-up, high stability and high yields. Several chiral borohydrides have been developed to efficiently achieve enantioselective and diastereoselective reductions of carbonyl compounds.

Metal borohydrides M(BH4)n (n is the valence of metal M) have high hydrogen density, and are therefore regarded as potential hydrogen storage material (Review: Recent Progress in Metal Hydrides for Hydrogen Storage, Li, H.- W. et al., Energies, 2011, 4, 185-214). Borohydrides have the potential to be used as fuel cells. Recent research is ongoing in direct borohydride fuel cells (DBFC). For portable applications, DBFC is a promising power system. Additional applications include waste water treatment and paper pulp bleaching.