Monoaldehydes

Monoaldehydes are organic compounds that contain a single aldehyde functional group (-CHO). Their general formula is R-CHO, where R is a hydrogen or a hydrocarbon substituent. When R is hydrogen, the compound is methanal (formaldehyde); when R is an alkyl or aryl group, the compound is an ordinary aldehyde such as ethanal (acetaldehyde), propanal (propionaldehyde), or benzaldehyde. Monoaldehydes can be aliphatic or aromatic and vary widely in volatility and polarity.

They are reactive at the carbonyl carbon, undergoing typical aldehyde reactions, including nucleophilic addition, oxidation to carboxylic acids, and reduction to primary alcohols. They can participate in aldol condensations and form acetals with alcohols under acidic conditions. They generally have higher boiling points than alkanes of similar molecular weight due to the polar C=O group, but do not form hydrogen-bonded networks as strongly as alcohols, so their boiling points are lower than alcohols of comparable size.

Common production methods include partial oxidation of primary alcohols and hydroformylation of alkenes to give aldehydes, followed by separation. Large-scale uses include formaldehyde resins and polymers; acetaldehyde as a chemical intermediate; and benzaldehyde in fragrances and flavorings, as well as in dyes and other syntheses.

Safety and handling: Many monoaldehydes are toxic or irritating. Formaldehyde is particularly hazardous and is a known carcinogen. Aldehydes are typically flammable and should be handled with appropriate precautions.