Acetic anhydride is an esterification agent for use in prepn. of modified food starch and for acetylation of monoglycerides. Acetic anhydride is a versatile reagent for acetylations, the introduction of acetyl groups to organic substrates. Acetic anhydride is the chemical compound with the formula (CH3CO)2O (commonly abbreviated Ac2O). Ac2O is mainly used for acetylations leading to commercially significant materials. Its largest application is for the conversion of cellulose to cellulose acetate, which is a component of photographic film and other coated materials. Similarly it is used in the production of aspirin, acetyl salicylic acid, which is prepared by the acetylation of salicylic acid. It is also used as a wood preservative via autoclave impregnation to make a longer lasting timber. Ac2O is also used in many industrial processes for the production of plastics, textiles, dyes, photochemical agents, perfumes, explosives and cigarette filters. Because of its use for the synthesis of heroin by the diacetylation of morphine, acetic anhydride (known as 'AA' in clandestine chemistry circles) is listed as a U.S. DEA List II Precursor, and restricted in many other countries.

Pyridine is a basic heterocyclic organic compound used as a solvent in organic synthesis. Since the pyridine ring has three double bonds, six p-electrons exist, which are sufficient for aromatic ring formation without involving the lone pair electrons of the nitrogen atom. Since the lone pair electrons remain free, quaternary salts retain the aromaticity. However, the nitrogen atom has a higher electronegativity than the carbon atoms and shows an electron-withdrawing effect. In oxidation and reduction reactions, the pyridine ring exhibits properties characteristic of pelectron-deficient aromatic rings: resistance to oxidation and facile reduction. Pyridine bases are a constituent of tars. They were isolated from coal tar or coal gas before synthetic manufacturing processes became established. Pyridine is an excellent solvent, especially for dehydrochlorination reactions and extraction of antibiotics. Large amounts of pyridine are used as starting material for pharmaceuticals and agrochemicals: for example, herbicides such as diquat and paraquat, insecticides such as chlorpyrifos, and fungicides such as pyrithione. Pyridine is harmful if inhaled, swallowed or absorbed through the skin. Effects of acute pyridine intoxication include dizziness, headache, lack of coordination, nausea, salivation, and loss of appetite.