Hydrogen Cyanide

Definition

Hydrogen cyanide, also known as hydrocyanic acid or prussic acid, is a highly toxic chemical compound composed of hydrogen and cyanide. It is a colorless, volatile liquid with a distinctive almond-like odor. Hydrogen cyanide is particularly relevant in the context of nucleophilic addition reactions and the formation of cyanohydrins.

5 Must Know Facts For Your Next Test

1. Hydrogen cyanide is a highly toxic substance that can cause rapid and potentially fatal poisoning if inhaled or ingested.
2. The nucleophilic addition of hydrogen cyanide to carbonyl compounds (aldehydes and ketones) is a key reaction in the formation of cyanohydrins.
3. Cyanohydrins are important synthetic intermediates in organic chemistry, as they can be further transformed into a variety of other useful compounds.
4. The mechanism of the nucleophilic addition of HCN to a carbonyl involves the initial attack of the cyanide ion (CN-) on the electrophilic carbon of the carbonyl, followed by the addition of a proton from the HCN molecule.
5. Cyanohydrin formation is a reversible reaction, and the equilibrium can be shifted by adjusting factors such as temperature, pH, and the presence of other reagents.

Review Questions

• Describe the role of hydrogen cyanide in the nucleophilic addition reaction leading to cyanohydrin formation.
  • In the nucleophilic addition reaction, hydrogen cyanide (HCN) acts as the nucleophile, with the cyanide ion (CN-) attacking the electrophilic carbon of the carbonyl compound (aldehyde or ketone). This addition reaction results in the formation of a new carbon-carbon bond and a hydroxyl group, creating a cyanohydrin product. The hydrogen from the HCN molecule is then added to the oxygen, completing the overall reaction mechanism.
• Explain how the reversible nature of the cyanohydrin formation reaction can be used to control the equilibrium and product distribution.
  • The cyanohydrin formation reaction is reversible, meaning the equilibrium can be shifted by manipulating various factors. For example, increasing the temperature or changing the pH can favor the reverse reaction, leading to the dissociation of the cyanohydrin back into the original carbonyl compound and hydrogen cyanide. Alternatively, the addition of other reagents or the removal of water can drive the equilibrium towards the formation of the cyanohydrin product. Understanding the reversible nature of this reaction allows organic chemists to control the product distribution and optimize the synthesis of desired compounds.
• Discuss the importance of cyanohydrins as synthetic intermediates in organic chemistry and provide examples of their further transformations.
  • Cyanohydrins are valuable synthetic intermediates in organic chemistry due to the versatility of the cyano and hydroxyl functional groups they contain. These compounds can undergo a variety of subsequent reactions, such as hydrolysis to form α-hydroxy acids, reduction to form α-hydroxy alcohols, or displacement reactions to form other substituted compounds. For instance, cyanohydrins can be converted to α-amino acids through a Strecker synthesis or used as precursors for the synthesis of various heterocyclic compounds. The ability to selectively transform cyanohydrins into a wide range of products makes them an important class of intermediates in the construction of complex organic molecules.

Related terms

Nucleophilic Addition: A type of organic reaction where a nucleophile adds to the carbon-carbon double bond of an electrophilic alkene or carbonyl compound, forming a new carbon-carbon or carbon-heteroatom single bond.

Cyanohydrin: An organic compound formed by the addition of hydrogen cyanide (HCN) to a carbonyl compound (aldehyde or ketone), resulting in the formation of a new carbon-carbon bond and a hydroxyl group.

Nucleophile: A species (atom, ion, or molecule) that donates an electron pair to form a new covalent bond in a chemical reaction.