dicarboxyliques

Dicarboxyliques, more commonly referred to in English as dicarboxylic acids, are organic compounds that contain two carboxyl groups (-COOH) in their structure. They can be aliphatic, with the two carboxyl groups attached to carbon chains such as HOOC-(CH2)n-COOH, or aromatic, with the groups attached to a benzene ring. They may be symmetric or unsymmetrical.

The IUPAC naming for aliphatic dicarboxylic acids follows the parent alkane with the suffix dioic acid, for example oxalic acid (ethanedioic acid), malonic acid (propanedioic acid), succinic acid (butanedioic acid), adipic acid (pentanedioic acid), and so on. Aromatic examples include phthalic acid (benzene-1,2-dicarboxylic acid), isophthalic acid (benzene-1,3-dicarboxylic acid), and terephthalic acid (benzene-1,4-dicarboxylic acid).

Properties of dicarboxylic acids vary with chain length and substitution. Short-chain examples such as oxalic acid are highly soluble in water and relatively strong in acidity, while longer-chain ones tend to be less soluble and have higher melting points. They are typically solid at room temperature and can form diesters or anhydrides upon heating or chemical reaction. In aqueous solution they can release two protons, with pKa values that depend on the specific compound.

Industrial relevance is wide. Dicarboxylic acids serve as monomers or intermediates in polymer production, notably in polyesters and polyamides. For instance, terephthalic and isophthalic acids are key monomers for PET and related polymers, while adipic acid is important in nylon production. Malonic and other diacids are used as building blocks in organic synthesis and as buffering or plating agents in some applications. Safety varies by compound; many are irritants and should be handled with appropriate precautions.