Chemistry:Sodium cyanide

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Sodium cyanide
Sodium cyanide bonding
Sodium-cyanide-phase-I-unit-cell-3D-SF.png
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
EC Number
  • 205-599-4
RTECS number
  • VZ7525000
UNII
UN number 1689
Properties
NaCN
Molar mass 49.0072 g/mol
Appearance white solid
Odor faint almond-like
Density 1.5955 g/cm3
Melting point 563.7 °C (1,046.7 °F; 836.9 K)
Boiling point 1,496 °C (2,725 °F; 1,769 K)
48.15 g/100 mL (10 °C)
63.7 g/100 mL (25 °C)
Solubility soluble in ammonia, methanol, ethanol
very slightly soluble in dimethylformamide, SO2
insoluble in dimethyl sulfoxide
1.452
Thermochemistry[1]
70.4 J·mol−1·K−1
115.6 J·mol−1·K−1
−87.5 kJ·mol−1
−76.4 kJ·mol−1
Hazards
Safety data sheet ICSC 1118
GHS pictograms GHS06: Toxic GHS09: Environmental hazard
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
4
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
6.44 mg/kg (rat, oral)
4 mg/kg (sheep, oral)
15 mg/kg (mammal, oral)
8 mg/kg (rat, oral)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 5 mg/m3[2]
REL (Recommended)
C 5 mg/m3 (4.7 ppm) [10-minute][2]
IDLH (Immediate danger)
25 mg/m3 (as CN)[2]
Related compounds
Other cations
Potassium cyanide
Related compounds
Hydrogen cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium cyanide is a poisonous compound with the formula NaCN. 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 high reactivity toward metals. It is a moderately strong base. When treated with acid, it forms the toxic gas hydrogen cyanide:

NaCN + H2SO4 → HCN + NaHSO4

Production and chemical properties

Sodium cyanide is produced by treating hydrogen cyanide with sodium hydroxide:[4]

HCN + NaOH → NaCN + H2O

Worldwide production was estimated at 500,000 tons in the year 2006. Formerly it was prepared by the Castner process involving the reaction of sodium amide with carbon at elevated temperatures.

NaNH2 + C → NaCN + H2

The structure of solid NaCN is related to that of sodium chloride.[5] The anions and cations are each six-coordinate. Potassium cyanide (KCN) adopts a similar structure. [6]

Because the salt is derived from a weak acid, sodium cyanide readily reverts to HCN by hydrolysis; the moist solid emits small amounts of hydrogen cyanide, which is thought to smell like bitter almonds (not everyone can smell it—the ability thereof is due to a genetic trait[7]). Sodium cyanide reacts rapidly with strong acids to release hydrogen cyanide. This dangerous process represents a significant risk associated with cyanide salts. It is detoxified most efficiently with hydrogen peroxide (H2O2) to produce sodium cyanate (NaOCN) and water:[4]

NaCN + H2O2 → NaOCN + H2O

Applications

Cyanide mining

Gold cyanidation (also known as the cyanide process) is the dominant technique for extracting gold, much of which is obtained from low-grade ore. More than 70% of cyanide consumption globally is used for this purpose. The application exploits the high affinity of gold(I) for cyanide, which induces gold metal to oxidize and dissolve in the presence of air (oxygen) and water, producing the salt sodium dicyanoaurate:[4]

4 Au + 8 NaCN + O2 + 2 H2O → 4 Na[Au(CN)2] + 4 NaOH

A similar process uses potassium cyanide (KCN, a close relative of sodium cyanide) to produce potassium dicyanoaurate (KAu(CN)2).

Chemical feedstock

Several commercially significant chemical compounds are derived from cyanide, including cyanuric chloride, cyanogen chloride, and many nitriles. In organic synthesis, cyanide, which is classified as a strong nucleophile, is used to prepare nitriles, which occur widely in many chemicals, including pharmaceuticals. Illustrative is the synthesis of benzyl cyanide by the reaction of benzyl chloride and sodium cyanide.[8]

Niche uses

Being highly toxic, sodium cyanide is used to kill or stun rapidly such as in widely illegal cyanide fishing and in collecting jars used by entomologists.

Toxicity

Main page: Medicine:Cyanide poisoning

Sodium cyanide, like other soluble cyanide salts, is among the most rapidly acting of all known poisons. NaCN is a potent inhibitor of respiration, acting on mitochondrial cytochrome oxidase and hence blocking electron transport. This results in decreased oxidative metabolism and oxygen utilization. Lactic acidosis then occurs as a consequence of anaerobic metabolism. An oral dosage as small as 200–300 mg can be fatal.

References

  1. CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data.. William M. Haynes, David R. Lide, Thomas J. Bruno (2016-2017, 97th ed.). Boca Raton, Florida. 2016. ISBN 978-1-4987-5428-6. OCLC 930681942. https://www.worldcat.org/oclc/930681942. 
  2. 2.0 2.1 2.2 NIOSH Pocket Guide to Chemical Hazards. "#0562". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0562.html. 
  3. "Cyanides (as CN)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/cyanides.html. 
  4. 4.0 4.1 4.2 Rubo, Andreas; Kellens, Raf; Reddy, Jay; Steier, Norbert; Hasenpusch, Wolfgang (2006). "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.i01_i01. 
  5. Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN:0-19-855370-6.
  6. H. T. Stokes; D. L. Decker; H. M. Nelson; J. D. Jorgensen (1993). "Structure of potassium cyanide at low temperature and high pressure determined by neutron diffraction". Phys. Rev. B 47 (17): 11082–11092. doi:10.1103/PhysRevB.47.11082. PMID 10005242. Bibcode1993PhRvB..4711082S. https://zenodo.org/record/1233725. 
  7. Online Mendelian Inheritance in Man (OMIM) 304300
  8. Adams, Roger; Thal, A. F. (1922). "Benzyl cyanide". Organic Syntheses 2: 9. doi:10.15227/orgsyn.002.0009. 

External links