Adipic acid

• BPAdipic Acid
• Ph. Eur.Adipic Acid
• USP–NFAdipic Acid

Acidum adipicum; adipinic acid; butane-1,4-dicarboxylic acid; hexanedioic acid; 1,4-butanedicarboxylic acid; E355

Hexanedioic acid · [124-04-9]

UNII 76A0JE0FKJ · PubChem CID 196

C6H10O4 · 146.14

pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Solid

Used as an acidulant and buffering agent in foods and medicines, and as the acid component of effervescent tablets and granules where its low hygroscopicity is an advantage. In hydrophilic matrix tablets it has been used to create an acidic microenvironment that gives more pH-independent release of weakly basic drugs. It is also a flavouring agent with a mild, tart taste.

White or almost white, odourless, non-hygroscopic crystals or crystalline powder with a slightly acidic taste.

Melting point

≈ 151–154 °C

pKa

pKa1 ≈ 4.4; pKa2 ≈ 5.4 (25 °C)

Solubility

sparingly soluble in cold water, freely soluble in boiling water; soluble in ethanol and methanol; very slightly soluble in hydrocarbons

Hygroscopicity

practically non-hygroscopic

Stable in the solid state. Store in a well-closed container in a cool, dry place.

Incompatible with strong oxidising agents and strong bases; as a dicarboxylic acid it reacts with alkaline materials and carbonates.

Made industrially by oxidising a mixture of cyclohexanol and cyclohexanone with nitric acid, followed by crystallisation; it is a major intermediate in nylon-6,6 production.

Of low oral toxicity and non-irritant at the levels used in food and medicines; it is largely excreted unchanged in the urine. JECFA has allocated an ADI of 0–5 mg/kg body weight. The dust may irritate the eyes and respiratory tract.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended; avoid dust formation, as fine dust can form explosive mixtures with air.

GRAS listed. Accepted as a food additive in Europe (E355). Included in the FDA Inactive Ingredient Database (oral preparations) and in non-parenteral medicines licensed in Europe.

Citric acid; fumaric acid; malic acid; succinic acid; tartaric acid.

Compared with citric and tartaric acids, adipic acid dissolves more slowly and is much less hygroscopic, so effervescent products made with it are less prone to premature reaction during storage but release carbon dioxide more slowly.