Nitric acid fuming nitric acid at concentrations above 86%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agent. Commercially available nitric acid is an azeotrope with water at a concentration of 68% HNO, which is the ordinary concentrated nitric acid of commerce. This
Sulfonic acid sulfonic acid derivatives of polystyrene and is used as catalysts and for ion exchange (water softening). Nafion, a fluorinated polymeric sulfonic acid is a component of proton exchange membranes in fuel cells. Antibacterial drugs sulfa drugs are produced from sulfonic acids. Methanesulfonic acid is used as the supporting electrolyte of the zinc-cerium and lead-acid (methanesulfonate) flow batteries. Sulfonic acids can be converted to esters. This class of organic compounds has the general formula R−SO−OR. Sulfonic esters such as methyl triflate are considered good alkylating agents in organic synthesis. Such sulfonate esters are often prepared by alcoholysis of the sulfonyl chlorides: