Potassium cyanate

Potassium cyanate is an inorganic compound with the formula KOCN (sometimes denoted KCNO[1]). It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was 20,000 tons in 2006.[2]

Potassium cyanate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.008.798
EC Number
  • 209-676-3
KEGG
RTECS number
  • GS6825000
UNII
Properties
KOCN
Molar mass 81.1151 g/mol
Appearance white, crystalline powder
Density 2.056 g/cm3
Melting point 315 °C (599 °F; 588 K)
Boiling point ~ 700 °C (1,292 °F; 973 K) decomposes
75 g/100 mL
Solubility very slightly soluble in alcohol
Structure
tetragonal
Hazards
R-phrases (outdated) R22
S-phrases (outdated) S24, S25
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
2
0
Lethal dose or concentration (LD, LC):
841 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Structure and bonding

The cyanate anion is isoelectronic with carbon dioxide and with the azide anion, being linear. The C-N distance is 121 pm, about 5 pm longer than for cyanide.[3][4] Potassium cyanate is isostructural with potassium azide.[5]

Structure of potassium azide,[6] which is isostructural with potassium cyanate.

Uses

For most applications, the potassium and sodium salts can be used interchangeably. Potassium cyanate is often preferred to the sodium salt, which is less soluble in water and less readily available in pure form.

Potassium cyanate is used as a basic raw material for various organic syntheses, including, urea derivatives, semicarbazides, carbamates and isocyanates. For example, it is used to prepare the drug hydroxyurea. It is also used for the heat treatment of metals (e.g., Ferritic nitrocarburizing).[2][7]

Therapeutic Uses

Potassium cyanate has been used to reduce the percentage of sickled erythrocytes under certain conditions and has also increased the number of deformalities. In an aqueous solution, it has prevented irreversibly the in vitro sickling of hemoglobins containing human erythrocytes during deoxygenization. Veterinarians have also found potassium cyanate useful in that the cyanate salts and isocyanates can treat parasite diseases in both birds and mammals.[8]

Preparation and reactions

KOCN is prepared by heating urea with potassium carbonate at 400 °C:

2 OC(NH2)2 + K2CO3 → 2 KOCN + (NH4)2CO3

The reaction produces a liquid. Intermediates and impurities include biuret, cyanuric acid, and potassium allophanate (KO2CNHC(O)NH2), as well as unreacted starting urea, but these species are unstable at 400 °C.[2]

Protonation gives a 97:3 mixture (at room temperature) of two tautomers, HNCO and NCOH. The former trimerizes to give cyanuric acid.

Properties

Potassium carbonate crystals are destroyed by the melting process so that the urea can react with almost all potassium ions to convert to potassium cyanate at a higher rate than when in the form of a salt. This makes it easier to reach higher purities above 95%. It can also be made by oxidizing potassium cyanide at a high temperature in the presence of oxygen or easily reduced oxides, such as lead, tin, or manganese dioxide, and in aqueous solution by reacting with hypochlorites or hydrogen peroxide. Another way to synthesize it is to allow an alkali metal cyanide to react with oxygen in nickel containers under controlled conditions. It can be formed by the oxidation of ferrocyanide. Lastly, it can be made by heating potassium cyanide with lead oxide.[9]

References
  1. Recreation of Wöhler’s Synthesis of Urea: An Undergraduate Organic Laboratory Exercise James D. Batchelor, Everett E. Carpenter, Grant N. Holder, Cassandra T. Eagle, Jon Fielder, Jared Cummings The Chemical Educator 1/Vol .3,NO.6 1998 ISSN 1430-4171 Online article Archived 2006-09-30 at the Wayback Machine
  2. Peter M. Schalke1, "Cyanates, Inorganic Salts" Ullmann's Encyclopedia of Industrial Chemistry2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a08_157.pub2. Article Online Posting Date: July 15, 2006
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. Jursík, F. (2001). Anorganická chemie nekovů (1. vydání). VŠCHT Praha. ISBN 80-7080-417-3
  5. T. C. Waddington "Lattice parameters and infrared spectra of some inorganic cyanates" J. Chem. Soc., 1959, 2499-2502. doi:10.1039/JR9590002499
  6. Ulrich Müller "Verfeinerung der Kristallstrukturen von KN3, RbN3, CsN3 und TIN3" Zeitschrift für anorganische und allgemeine Chemie 1972, Volume 392, 159–166. doi:10.1002/zaac.19723920207
  7. INEOS Paraform GmbH, Potassium Cyanate (KOCN) product information. Online version accessed on 2009-06-30.
  8. "Potassium Cyanate"
  9. "Potassium cyanate" https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=11378442&loc=ec_rcs
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