Cyanocarbon

Cyanocarbons are a chemical compounds that contain several cyanide groups. Such substances generally are classified as organic compounds, since they are formally derived from hydrocarbons by replacing one or more hydrogen atoms with a cyanide. The parent member is C(CN)₄. Organic chemists often refer to cyanides as nitriles.

In general, cyanide is an electronegative substituent. Thus, for example, cyanide-substituted carboxylic acids tend to be stronger than the parents. The cyanide group also stabilizes anions by delocalizing negative charge as revealed by resonance structures.

Definition and examples

Cyanocarbons are organic compounds bearing enough cyano functional groups to significantly alter their chemical properties. ^[1]

Important cyanocarbons:

• tetracyanoethylene, which readily reduces to a stable anion, unlike most ethene derivatives
• Pentacyanocyclopentadiene, which forms a stable anion by ionization of the C-H bond.
• tetracyanoethylene oxide, an electrophilic epoxide that undergoes ready scission of its C-C bond.
• tetracyanoquinodimethanide, C₆H₄-1,4-(C(CN)₂)₂, a powerful electron acceptor.

Tricyanomethane

Tricyanomethane (NC)₃CH is a hypothetical molecule that has thus far resisted all attempts at synthesis . It would rank as one of the most acidic of the carbon acids with an estimated Pka of -5. The reaction of sulfuric acid with sodium tricyanomethanide in water (a reaction first tried by H. Schmidtmann in 1896 with inconclusive results ^[2]) is reported to result in the formation of de hydrate (NC)₃C^-H₃O⁺ or the formation of (Z)-3- amino-2-cyano-3-hydroxyacrylamide (H₂N)(OH)C=C(CN)CONH₂ depending on the precise conditions ^[3]. The reaction of HCl gas with sodium tricyanomethanide dissolved in THF is reported to yield 1-chloro-1-amino-2,2-dicyanoethylene ((NC)₂C=C(NH₂)Cl) and its tautomer.

References

1. ^ W. Webster, O. W. “Cyanocarbons: A Classic Example of Discovery-Driven Research” Journal of Polymer Science Part A: Polymer Chemistry 2001, Volume 40, Pages 210 - 221.doi:10.1002/pola.10087
2. ^ Schmidtmann, H. (1896). "Ueber einige Derivate des Malonitrils". Berichte der deutschen chemischen Gesellschaft 29 (2): 1168. doi:10.1002/cber.18960290204. 
3. ^ Šišak, Dubravka; McCusker, Lynne B.; Buckl, Andrea; Wuitschik, Georg; Wu, Yi-Lin; Schweizer, W. Bernd; Dunitz, Jack D. (2010). "The Search for Tricyanomethane (Cyanoform)". Chemistry - A European Journal 16 (24): n/a. doi:10.1002/chem.201000559. PMID 20480465.