13phthalic

13phthalic is a nonstandard or historic designation that usually refers to isophthalic acid, the meta isomer of phthalic acid. In modern nomenclature it is called 1,3-benzenedicarboxylic acid, and is often abbreviated as isophthalic acid. It is one of three isomeric benzenedicarboxylic acids collectively known as phthalic acids; the others are the ortho isomer (1,2-benzenedicarboxylic acid) and the para isomer (1,4-benzenedicarboxylic acid).

Chemical properties: Isophthalic acid has the molecular formula C8H6O4 and consists of a benzene ring bearing two carboxyl groups at the 1 and 3 positions. It is a white crystalline solid with a relatively high melting point and low solubility in water, though it dissolves in hot water and several organic solvents. It is a dicarboxylic acid and can form various esters and acid salts.

Production and uses: Industrially, isophthalic acid is produced by oxidation of meta-xylene and related derivatives. It is a key monomer in the manufacture of polyesters and alkyd resins, often used in combination with terephthalic acid to tailor polymer properties. It also serves as a precursor to isophthalate esters used as plasticizers or crosslinkers in coatings and resins.

Safety and handling: Isophthalic acid is an irritant and should be handled with appropriate personal protective equipment to avoid skin, eye, and respiratory exposure. It is not highly acutely toxic but may cause irritation upon contact or inhalation. Standard industrial hygiene practices apply.