Toluene diisocyanate (TDI) is an organic compound with the formula CH3C6H3 (NCO) 2 and a member of Isocyanates, which is chemically related to polyurethanes. To sensitize TDI, 2, 4-TDI is prepared in three steps from toluene via dinitrotoluene and 2,4-diaminotoluene (TDA). Finally, the TDA is subjected to phosgenation, i.e., treatment with phosgene to form TDI.

This final step produces HCl as a byproduct and is a major source of industrial hydrochloric acid. TDA, in turn, reacts with carbonyl dichloride (CDC) to produce toluene diisocyanate (TDI). Toluene diisocyanate produced in Karun is an 80/20 mixture of 2,4-TDI (CAS: 584-84-9) and 2,6-TDI (CAS: 91-08-7) isomers with purity of at least 99.5%.