Ammoniumryhmän

Ammoniumryhmän, in Swedish chemical nomenclature, refers to the ammonium group, the positively charged nitrogen-containing moiety that arises when ammonia or an amine is protonated. In chemistry, it encompasses the ammonium cation NH4+ and, more broadly, protonated amine groups of the form RNH3+ or R2NH2+. A quaternary ammonium group, R4N+, is also part of this family, though it lacks N–H bonds.

The ammonium group is typically described as a nitrogen atom bearing hydrogen atoms or carbon substituents with an overall positive charge. Ammonium ions in solution interconvert with their neutral amine forms depending on pH, with the conjugate acid–base pair NH4+/NH3 having a pKa around 9–11 in water. Primary, secondary, and tertiary ammonium species differ in geometry: NH4+ is approximately tetrahedral, while protonated amines RNH3+ are pyramidal with varying bond angles.

Occurrence and significance are broad. In biochemistry, the amino group of amino acids is protonated to form an NH3+ group at physiological pH, contributing to protein structure and charge interactions. Quaternary ammonium groups, such as in acetylcholine or many polymers, carry a permanent positive charge and play key roles in neurotransmission, catalysis, and material science. In industry, ammonium salts and quaternary ammonium compounds are used as fertilizers, surfactants, phase-transfer catalysts, and in ion-exchange resins.

Terminology notes: the term ammonium group often refers to the protonated, positively charged nitrogen moiety across various contexts, from simple ammonium salts to protonated amines and permanently charged quaternary ammonium species.