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.

Toluene is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a CH3 group attached to a phenyl group. The major use of toluene is as a mixture added to gasoline to improve octane ratings. Toluene is also usedto produce benzene and as a solvent in paints, coatings, synthetic fragrances, adhesives, inks, and cleaningagents. Toluene is also used in the production of polymers used to make nylon, plastic soda bottles, andpolyurethanes and for pharmaceuticals, dyes, cosmetic nail products, and the synthesis of organicchemicals. The CNS is the primary target organ for toluene toxicity in both humans and animals for acute and chronicexposures. CNS dysfunction (which is often reversible) and narcosis have been frequently observed inhumans acutely exposed to low or moderate levels of toluene by inhalation; symptoms include fatigue,sleepiness, headaches, and nausea. CNS depression and death have occurred at higher levels of exposure. Toluene is used in veterinary medicine as a treatment for various parasites in dogs and cats. It is used for the removal of ascarids (Toxocara canis and Toxascaris leonina) and hookworms (Ancylostoma caninum and Uncinaria stenocephala) and as an aid in removing tapeworms (Taenia pisiformis, Dipylidium caninum, and Echinococcus granulosus) from dogs and cats.