Nomenclature
CAS number: 16949-15-8
Lithium tetrahydroborate.
BH
4Li; mol wt 21.78.
B 49.64%, H 18.51%, Li 31.87%.
LiBH
4.
Description and references
Prepd by the action of diborane on ethyllithium;
by the action of aluminum borohydride on ethyllithium: Schlesinger,
Brown, J. Am. Chem. Soc. 62, 3429-35 (1940). Review of lithium and other metal tetrahydroborates:
James, Wallbridge, Prog. Inorg. Chem. 11, 99-231 (1970).
Properties
Orthorhombic crystals, mp 268°; dec 380°. d 0.66. Stable under ordinary conditions, but
dec in moist air. Dangerous when wet. Reacts with hydrogen chloride to form hydrogen, diborane, and lithium
chloride; forms lithium boromethoxide and hydrogen with methyl alcohol.
Sol in water at pH >7. Aq solns dec slowly if the pH is >7,
and rather vigorously when acidified. Sol in ether, tetrahydrofuran,
aliphatic amines.Use
Strong reducing agent. Used in the reduction of
compds contg ketonic, aldehydic, or ester carbonyls and a nitrile
group, where reduction of the carbonyl, but not of the nitrile group,
is wanted. In the determination of free carboxyl groups in peptides
and proteins; after esterification and acetylation, only the ester
groups, and none of the peptide bonds are reduced.