Sodium cyanoborohydride Property

Melting point:

>242 °C (dec.) (lit.)

Boiling point:

307°C

Density 

1.083 g/mL at 25 °C

Flash point:

−1 °F

storage temp. 

Store below +30°C.

solubility 

Soluble in water (100 mg/ml, with heating), methanol, ethanol, and THF. It is insoluble in nonpolar solvents such as benzene or hexane

form 

Powder

color 

White

Specific Gravity

1.2

Water Solubility 

2120 g/L at 29 ºC (dec.)

Sensitive 

Moisture Sensitive

Merck 

14,8606

BRN 

4152656

Stability:

Stable. Hygroscopic. Reacts violently with water, giving off and igniting hydrogen. Do not use water on fires involving this chemical - instead use dry soda ash. Incompatible with strong acids, water, strong oxidizing agents.

CAS DataBase Reference

25895-60-7(CAS DataBase Reference)

EPA Substance Registry System

Borate(1-), (cyano-.kappa.C)trihydro-, sodium, (T-4)- (25895-60-7)

Safety

Hazard Codes 

T+,N,T,F

Risk Statements 

26/27/28-32-34-50/53-16-15-11-51/53-36-23/24/25-19-14-40-36/37/38

Safety Statements 

26-28-36/37/39-45-60-61-8-50A-43-28A-1-16-36/37

RIDADR 

UN 3179 4.1/PG 2

WGK Germany 

1

F 

10-21

Hazard Note 

Toxic/Highly Flammable

TSCA 

Yes

HazardClass 

6.1

PackingGroup 

I

HS Code 

28500020

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H228Flammable solid

H260In contact with water releases flammable gases which may ignite spontaneously

H314Causes severe skin burns and eye damage

H410Very toxic to aquatic life with long lasting effects

Precautionary statements

P210Keep away from heat/sparks/open flames/hot surfaces. — No smoking.

P231+P232Handle under inert gas. Protect from moisture.

P260Do not breathe dust/fume/gas/mist/vapours/spray.

P280Wear protective gloves/protective clothing/eye protection/face protection.

P303+P361+P353IF ON SKIN (or hair): Remove/Take off Immediately all contaminated clothing. Rinse SKIN with water/shower.

P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.

Sodium cyanoborohydride Chemical Properties,Usage,Production

Description

Sodium cyanoborohydride (NaBH3CN) is a selective reducing agent used for a variety of chemical reductions, including aldehyde, ketones, acetals, epoxides, oximes, enamines, reductive aminations of aldehydes and ketones, and reductive alkylations of amines and hydrazines. The utility of sodium cyanoborohydride as a reducing agent is greatly enhanced by its stability under acid conditions, and its solubility in aprotic solvents. Sodium cyanoborohydride is a milder and more selective reducing agent than sodium borohydride.
Sodium cyanoborohydride is a weaker and more-selective reducing agent than sodium borohydride because of the electron-withdrawing effect of the cyano group. It has the further advantage that it is stable in acid to pH = 3 and can be employed to effect reductions in the presence of functional groups that are sensitive to the more-basic conditions of reduction with sodium borohydride.
Aldehydes and ketones are unaffected by sodium cyanoborohydride in neutral solution, but they are readily reduced to the corresponding alcohol at pH=3-4 by way of the protonated carbonyl group. By previous exchange of the hydrogens of the borohydride for deuterium or tritium, by reaction with D2O or tritiated water, an efficient and economical route is available for deuteride or tritiide reduction of aldehydes and ketones.

Chemical Properties

Sodium cyanoborohydride is a white or slightly yellow solid powder, It is a versatile reducing agent stable in aqueous solution at pH 7.2. It is a weaker reducing agent as compared to NaBH4. It effectively reduces Schiff bases. NaCNBH4 participates in the reductive methylation for the efficient and selective conversion of the e-amino groups of lysyl residues in proteins to the mono- and dimethyl derivatives.

Physical properties

Sodium cyanotrihydridoborate, sodium cyanoborohydride, sodium cyanoboranate, NaBH3CN, is a white, amorphous powder, melting with decomposition at 240 – 242℃. Contact with the atmosphere must be avoided as it is extremely hygroscopic. It is very soluble in polar, especially protic, solvents such as water, alcohols, amines, and THF, but not in diethyl ether or hydrocarbons.

Uses

Sodium Cyanoborohydride is a commonly used as a reagent in the reductive amination of aldehydes and ketones and in the reductive alkylation of amines. It is also used in the synthesis of a novel phenolate-bridged dilanthanum(III) complex of interest as a model for metalloproteins as well as for its importance in basic and applied chemistry.

Preparation

Synthesis of Sodium cyanoborohydride(NaBH3CN): NaBH3CN was made by stirring equimolar BH3·THF (~1 M) with NaCN in THF in excellent yield.To a rapidly stirred slurry of sodium borohydride (80.2g, 2.09 mol) in THF (1000mL) in a 2-L flask is added a solution of hydrogen cyanide in THF (294g containing 58.8g of hydrogen cyanide) at 25°C. Evolution of hydrogen occurs slowly during the addition. Following the addition, the reaction mixture is stirred for 1 h at 25°C and then heated at reflux until hydrogen evolution has ceased. Filtration followed by vacuum removal of THF gives white solid sodium cyanoborohydride; yield 120g (91%).

Reactions

Sodium cyanoborohydride are frequently used for reductive aminations. Since the reaction rate for the reduction of iminium ions is much faster than for ketones or even aldehydes, the reductive amination can be carried out as a one-pot procedure by introducing the reducing agent into a mixture of the amine and carbonyl compound.
Contact with strong acids liberates the highly toxic gas HCN. A safer reducing agent with comparable reactivity is sodium triacetoxyborohydride. Reduction with Sodium Cyanoborohydride:
Tin-free Giese reaction of alkyl iodides with electron-deficient alkenes and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. Transfer of iodine followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism.
Borch and co-workers showed that sodium cyanoborohydride and lithium cyanoborohydride are acid-stable reagents capable of rapidly reducing carbonyl compounds to alcohols at pH 3-4, presumably via a protonated carbonyl cation.
With care to maintain a pH of 6-7, a mixture of a ketone or aldehyde reactant, an amine, and sodium cyanohydride provides products of reductive amination selectively, without competitive reduction of the carbonyl substrate. Though the conditions of the Borch reduction are mild, sodium cyanoborohydride is highly toxic, as are its byproducts. The pH was maintained by addition of HCl and/or KOH as needed using bromocresol green as an indicator.

Hazard

Flammable solid. Dust may form explosive mixture with air. Fire-water run-off in sewers may create fire or explosion hazard. This product is toxic. Severe corrosive hazard. Water used for fire extinguishing, which has been in contact with the product, may be corrosive.

Chemical Reactivity

Sodium cyanoborohydride is used as a selective reducing agent in the synthesis of pharmaceuticals. Its special reducing properties arise from its remarkable resistance to hydrolysis. It is stable even at pH 3 in water and methanol, its rate of hydrolysis being slower than that of NaBH4 by a factor of 108. Reactivity and stereoselectivity are considerably affected by the nature and acidity of the solvent. In polar aprotic solvents such as hexamethylphosphoric triamide (HMPT) or dimethyl sulfoxide (DMSO) it reduces aliphatic halides and toluenesulfonates to the corresponding hydrocarbons. Under these conditions other reducible functional groups such as epoxides, ketones, and aldehydes are unaffected.

Purification Methods

Sodium cyanoborohydride (10g) is dissolved in THF (80mL) and 1 M methanolic hydrochloric acid is added until pH reaches 9. The solution is then poured with stirring into dioxan (250mL). The precipitate is collected and stirred for 2 h in ethyl acetate (250mL). This solution is filtered, heated to reflux on a steam bath and then dioxan (150mL) is added slowly with swirling. This solution is slowly cooled to room temperature, chilled and filtered. The crystalline dioxan complex is dried in vacuo for 4 h at room temperature, then for 4 h at 80° C; yield 6.74g, purity >98% sodium cyanoborohydride by iodometric titration.