Sodium cyanoborohydride is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula Na B H₃ CN. It is a colourless salt, but commercial samples can appear tan. It is widely used in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

for the reduction of

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...

s. The salt tolerates aqueous conditions.

Use

Owing to the presence of the electron-withdrawing

cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...

substituent, (CN)H₃sup>− is less reducing than is H₄sup>−. As a mild reducing agent, it is used to convert

s to

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...

s. It is especially favored for

reductive amination Reductive amination (also known as reductive alkylation) is a form of amination that involves the conversion of a carbonyl group to an amine via an intermediate imine. The carbonyl group is most commonly a ketone or an aldehyde. It is considered ...

s, wherein aldehydes or ketones are treated with an amine in the presence of this reagent: : R₂CO + R'NH₂ + NaBH₃CN + CH₃OH → R₂CH-NHR' + "NaCH₃OBH₂CN" The reagent is typically used in excess. Selectivity is achieved at mildly basic solutions ( pH 7–10). The reagent is ideal for

s ("Borch Reaction"). In conjunction with tosylhydrazine, sodium cyanoborohydride is used in the reductive deoxygenation of

ketones In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double b ...

Structure and preparation

The tetrahedral BH₃(CN)⁻ comprises the anionic component of the salt. The reagent is often purchased, although it can be prepared easily. One method involves combining

sodium cyanide Sodium cyanide is a poisonous compound with the formula Na C N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its hi ...

and

borane Trihydridoboron, also known as borane or borine, is an unstable and highly reactive molecule with the chemical formula . The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated ...

. Another route entails treating sodium borohydride with

mercury(II) cyanide Mercury(II) cyanide, also known as mercuric cyanide, is a compound of mercury. It is an odorless, toxic white powder. It is highly soluble in polar solvents such as water, alcohol, and ammonia; slightly soluble in ether; and insoluble in benzene ...

. The commercial samples can be purified, but the yields of the reductive aminations do not improve.

References

Borohydrides Sodium compounds Reducing agents {{inorganic-compound-stub

Use

Structure and preparation

See also

References