R2COHCN

R2COHCN, commonly written as R2C(OH)CN, denotes the cyanohydrin functional group. It is formed when a carbonyl compound, such as an aldehyde or a ketone, reacts with hydrogen cyanide to give a carbon atom bearing both a hydroxyl group and a nitrile group, along with two organic substituents (R groups). In this general form the central carbon is tetravalent and carries two carbon-based substituents, a hydroxyl group, and a nitrile substituent.

Formation and characteristics: The reaction of a carbonyl compound with hydrogen cyanide is a nucleophilic addition that proceeds under acid or base catalysis and is often reversible. Because hydrogen cyanide is highly toxic, safer cyanide sources or surrogate reagents (such as acetone cyanohydrin or trimethylsilyl cyanide in the presence of a proton source) are frequently used in practice. Acetone cyanohydrin, for example, is a common, more stable surrogate formed from acetone and HCN.

Reactivity and transformations: Cyanohydrins serve as versatile intermediates in organic synthesis. The nitrile group can be converted to various functionalities, including amines, carboxylic acids, or amides, while the hydroxyl-bearing carbon can participate in further functionalization. They are valuable for constructing alpha-hydroxy nitriles, which are useful building blocks in the preparation of pharmaceuticals, natural products, and chiral auxiliaries. Under certain conditions, cyanohydrins may decompose or release HCN, highlighting the need for careful handling.

Applications and significance: Cyanohydrins like R2COHCN are leveraged as precursors in asymmetric synthesis and as routes to downstream products such as amino alcohols, mandelic derivatives, and other valuable intermediates. They illustrate a key strategy in converting carbonyl compounds into more functionalized, multi-heteroatom products.

Safety: Handling cyanohydrins and hydrogen cyanide requires appropriate safety measures due to toxicity and potential release of HCN under certain conditions.