OPA is a mixture of

isopropyl alcohol Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable organic compound with a pungent alcoholic odor. As an isopropyl group linked to a hydroxyl group (chemical formula ) it is the simple ...

and

isopropylamine Isopropylamine (monoisopropyl amine, MIPA, 2-Propylamine) is an organic compound, an amine. It is a hygroscopic colorless liquid with ammonia-like odor. It is miscible with water and flammable. It is a valuable intermediate in chemical industry. ...

that is used in the production of the

sarin Sarin (NATO designation GB G-series, "B"">Nerve_agent#G-series.html" ;"title="hort for Nerve agent#G-series">G-series, "B" is an extremely toxic synthetic organophosphorus compound.nerve agent Nerve agents, sometimes also called nerve gases, are a class of organic chemicals that disrupt the mechanisms by which nerves transfer messages to organs. The disruption is caused by the blocking of acetylcholinesterase (AChE), an enzyme that ...

. The mixture reacts with

methylphosphonyl difluoride Methylphosphonyl difluoride (DF), also known as EA-1251 or difluoro, is a chemical weapon precursor. Its chemical formula is CH3POF2. It is a List of Schedule 1 substances (CWC), Schedule 1 substance under the Chemical Weapons Convention. It is ...

to produce sarin.

References

Nerve agent precursors Chemical warfare agent mixtures {{chem-stub