aldehydi

Aldehydes are a class of organic compounds characterized by a carbonyl group (C=O) bonded to at least one hydrogen atom. The general structural formula is R-CHO, where R represents an alkyl or aryl group. The carbonyl carbon in aldehydes is highly electrophilic, making these compounds prone to nucleophilic addition and useful in a variety of chemical transformations.

Aldehydes are named by replacing the suffix of the parent chain with -al; common names are often used for simple members. Well-known aldehydes include formaldehyde (methanal, H2C=O), acetaldehyde (ethanal, CH3-CHO), and benzaldehyde (C6H5-CHO). They are typically volatile liquids or gases with characteristic sharp or distinctive odors; formaldehyde is pungent, while benzaldehyde has an almond-like scent.

In organic synthesis, aldehydes participate in many reactions. They can undergo aldol reactions to form β-hydroxy aldehydes and, upon dehydration, α,β-unsaturated aldehydes. Aldehydes can be oxidized to carboxylic acids or reduced to primary alcohols. They form acetals with alcohols under acidic conditions and react with amines to give imines or Schiff bases. Analytical tests such as Tollens’ test exploit the tendency of aldehydes to be oxidized.

Production and occurrence: industrially, aldehydes are produced by the oxidation of primary alcohols (for example, methanol to formaldehyde, ethanol to acetaldehyde) or by hydroformylation of alkenes followed by partial oxidation. Some aldehydes occur naturally in fruits, spices, and essential oils, and many are important as flavorings, fragrances, or intermediates in resins and plastics.

Safety: aldehydes vary in toxicity. Formaldehyde is a hazardous irritant and potential carcinogen; many aldehydes are flammable and require proper ventilation and handling.