Sulfonihapot

Sulfonihapot, known in English as sulfonic acids, are a class of organosulfur compounds that contain the sulfonyl functional group, −SO3H, attached to an organic residue. The general formula is RSO3H, where R can be an alkyl, aryl, or more complex group. They are typically strong Brønsted acids, with pKa values around the negative to near-zero range, making them among the strongest common organic acids. In many cases they exist as the neutral acid or as water-soluble salts.

Structure and properties are characterized by resonance-stabilized −SO3H groups. The group withdraws electron density, contributing to acidity and often to the chemical reactivity of the molecule. Many sulfonic acids are solids or liquids that are readily soluble in water when in their acidic form or as salts. They are frequently stable to air and moisture, but corrosive and should be handled with appropriate safety precautions.

Preparation methods are primarily industrial sulfonation of hydrocarbons. This is commonly accomplished by treating arenes or alkanes with sulfuric acid or oleum (fuming sulfuric acid) at elevated temperatures to yield aryl sulfonic or alkyl sulfonic acids, such as benzenesulfonic acid, toluenesulfonic acid, or methanesulfonic acid. They can be converted into a range of derivatives, including sulfonyl chlorides, sulfonamides, and sulfonate esters, expanding their use as intermediates in organic synthesis.

Applications are broad: detergents and surfactants frequently use alkylbenzenesulfonates and related sulfonates; sulfonic acids are key intermediates in dye, pharmaceutical, and polymer chemistry; and sulfonated resins serve in ion-exchange and catalysis.

Examples include benzenesulfonic acid, p-toluenesulfonic acid, and methanesulfonic acid. Safety concerns include their strong acidity and corrosivity; appropriate handling and protective equipment are required.