Cyanocarbon

In organic chemistry, cyanocarbons are a group of chemical compounds that contain several cyanide functional 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 group.[1] One of the simplest member is C(CN)₄ (tetracyanomethane, also known as carbon tetracyanide). 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 can also stabilize 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]

Illustrative cyanocarbons:

• Tetracyanoethylene, which reduces to a stable anion [C₂(CN)₄]^-, unlike most derivatives of ethylene.
• Pentacyanocyclopentadiene, which forms an air-stable anion, in contrast to cyclopentadiene.
• Tetracyanoethylene oxide, an electrophilic epoxide that undergoes ready scission of its C-C bond.[2]
• Tetracyanoquinodimethane, C₆H₄-para-(C(CN)₂)₂, which reduces to a stable anion, unlike most quinones.
• Cyanoform (tricyanomethane), HC(CN)₃
• Pentacyanopropenide, [(NC)₂C=C(CN)−C(CN)₂]^−.[3]

References

1. Webster, Owen W. "Cyanocarbons: a classic example of discovery-driven research" Journal of Polymer Science, Part A: Polymer Chemistry 2001, volume, 40, pp. 210-221. doi:10.1002/pola.10087
2. Linn, W. J. (1969). "Tetracyanoethylene Oxide". Organic Syntheses. 49: 103. doi:10.15227/orgsyn.049.0103.
3. Middleton, W. J.; Wiley, D. W. (1961). "Tetramethylammonium 1,1,2,3,3-Pentacyanopropenide". Org. Synth. 41: 99. doi:10.15227/orgsyn.041.0099.