Sodium cyanoborohydride
| Names | |
|---|---|
| IUPAC name
Sodium cyanoborohydride
| |
| Other names
Sodium borocyanohydride
Sodium cyanotrihydridoborate | |
| Properties | |
| NaBH3CN | |
| Molar mass | 62.84 g/mol |
| Appearance | White hygroscopic solid |
| Odor | Odorless |
| Density | 1.12 g/cm3 (25 °C) |
| Melting point | 241 °C (466 °F; 514 K) (decomposition) |
| Boiling point | Decomposes |
| 212 g/100 ml (29 °C) | |
| Solubility | Soluble in methanol, THF Sparingly soluble in ethanol Insoluble in benzene, diethyl ether, heptane, hexane, toluene, xylene |
| Solubility in diglyme | 17.6 g/100 ml (25 °C)[1] |
| Solubility in tetrahydrofuran | 37.7 g/100 ml (28 °C)[2] |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | 70 °C (158 °F; 343 K) |
| Related compounds | |
| Related compounds
|
Sodium borohydride |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Sodium cyanoborohydride is an inorganic chemical compound with the formula NaBH3CN, used as a reducing agent in organic synthesis for the reduction of imines.
Contents
Properties
Chemical
Sodium cyanoborohydride can be used to reduce imines, as well as aldehydes, ketones, oximes, enamines. Owing to the presence of the electron-withdrawing cyanide substituent, cyanoborohydride is less reducing than borohydride. As such, it does not reduce amides, ethers, lactones, nitriles, nitro compounds and epoxides.
Aldehydes and ketones are unaffected by sodium cyanoborohydride in neutral solution, but they are readily reduced to the corresponding alcohol at a pH between 3 and 4 by way of the protonated carbonyl group.
Sodium cyanoborohydride resists hydrolysis in water, although prolonged contact with moisture will cause decomposition. It is stable in acidic solution with a pH higher than 3.
Physical
Sodium cyanoborohydride is a hygroscopic white solid, soluble in water and THF.
Availability
Sodium cyanoborohydride can be bought from chemical suppliers.
Preparation
Sodium cyanoborohydride ca be prepared by reacting sodium cyanide with borane. The reaction takes place in anhydrous THF.[3]
A direct route, but very dangerous, involves reacting hydrogen cyanide with sodium borohydride. This is done by adding a THF solution of HCN to a slurry of NaBH4 in THF. Following the addition, the reaction mixture is stirred for 1 h at 25 °C, during which hydrogen is slowly produced. After the stirring is complete, the mixture is heated at reflux until hydrogen evolution has ceased. Filtration followed by vacuum removal of THF gives white solid sodium cyanoborohydride. Yield of this reaction is 91 %.[4]
Another route entails treating sodium borohydride with mercury(II) cyanide.
Projects
- Reduction of imines
- Reductive aminations
Handling
Safety
Sodium cyanoborohydride is toxic if ingested, as it contains cyanide. It is flammable.
Storage
In closed airtight bottles. Can also be kept in a desiccator, where it should be dry.
Disposal
Can be neutralized by carefully oxidizing the compound.
References
- ↑ Общая органическая химия. - Т. 6, под ред. Бартона Д. и Оллиса В.Д. - М.: Химия, 1984 (General organic chemistry. - T. 6, ed. Barton D. and Ollis W.D. - M.: Chemistry, 1984)
- ↑ Общая органическая химия. - Т. 6, под ред. Бартона Д. и Оллиса В.Д. - М.: Химия, 1984 (General organic chemistry. - T. 6, ed. Barton D. and Ollis W.D. - M.: Chemistry, 1984)
- ↑ Benjamin C. Hui, Synthesis and properties of borohydride derivatives, Inorg. Chem. 19, 3185-3186 (1980)
- ↑ Lane, C. F., Synthesis 135 (1975)
