dialdehyde

A dialdehyde is an organic compound that contains two aldehyde functional groups (-CHO) in the same molecule. The aldehyde groups can be located at different positions on the carbon skeleton, such as at the ends of an aliphatic chain or on adjacent or opposite positions of an aromatic ring. The general structural motif is R-(CHO)2, where R is the remainder of the molecule.

Common examples include glyoxal (ethane-1,2-dial), malonaldehyde (propane-1,3-dial), glutaraldehyde (pentane-1,5-dial), succinaldehyde (butane-1,4-dial), and aromatic dialdehydes such as o-phthalaldehyde (1,2-benzenedialdehyde) and terephthalaldehyde (1,4-benzenedialdehyde). These compounds vary in volatility, color, and reactivity, but all contain two formyl groups that confer high electrophilicity.

Preparation methods include oxidation of vicinal diols or diols-containing substrates with periodic acid or related oxidants; ozonolysis of alkenes followed by oxidative workup; and various selective oxidations of di-substituted hydrocarbons to install two aldehyde groups. Glyoxal can be produced by oxidation of glycol, while more complex dialdehydes are prepared by functional-group interconversions of suitable precursors.

Dialdehydes are used as crosslinking agents in polymers and resins, as components in coatings and plastics, and as fixatives in biology (notably glutaraldehyde). Aromatic dialdehydes such as o-phthalaldehyde are used in fluorescence-based amino acid detection and labeling. Their two aldehyde moieties enable diverse reactions, such as condensation with nucleophiles and formation of acetals or Schiff bases.

Safety-wise, dialdehydes are typically reactive and can be irritants or toxic; they may polymerize or form haze upon exposure to light or air. They are handled under appropriate controls to prevent inhalation, skin contact, or uncontrolled reactions.