2,2,4-Trimethyl-1,2-dihydroquinoline (usually abbreviated TMQ, known historically as Acetone-anil) is an aminic antioxidant commonly used as a stabiliser in rubbers and some plastics.

[1] The structure of TMQ is often represented by the monomer; however, the commercial material is typically a complex mixture of oligomers.

It is a good antioxidant, but it gives low protection against flex cracking (fatigue) and is not effective as an antiozonant.

The high molecular weight of TMQ oligomers makes them non-volatile and therefore more effective as long term heat-protection agents.

TMQ is relatively inert towards the cross-linking peroxides used to produce EPDM, or PEX and it therefore also sees use in these polymers.