Toluene

Toluene (C₇H₈) is methylbenzene — benzene with a single methyl group, the affable younger brother of the aromatic family. That one substituent makes it far less toxic than benzene, turning it into the most relied-upon workhorse solvent on the shop floor. It quietly supplies feedstock for TNT, TDI (polyurethane), and benzene itself. Boiling at 110.6°C with a sweet aroma, it dissolves almost anything — yet it carries the shadow of being the main component of paint thinner.