aminoryhmän

The aminoryhmä, known in chemistry as the amino group, is a functional group consisting of a nitrogen atom bonded to one or more carbon atoms. The simplest form is the primary amine with the formula -NH2, while secondary and tertiary amines have -NHR and -NR2, respectively. Amino groups occur widely in organic molecules, including aliphatic amines such as methylamine and ethylamine, and aryl amines such as aniline. In naming, the amino group is often used as a substituent, described with the "amino-" prefix in IUPAC nomenclature, and the term aminoryhmä is the Finnish equivalent of this concept.

Chemical properties of the amino group are dominated by the lone pair on nitrogen, which makes it both basic and nucleophilic. In aqueous solution, amino groups tend to accept protons to form ammonium ions (-NH3+). The pKa of the conjugate acid for most primary aliphatic amines lies around 9–11, so at physiological pH they are largely protonated, while the neutral -NH2 form becomes more prominent at higher pH. Aliphatic amines are typically more basic than aromatic amines, since conjugation of the lone pair with an aromatic ring (as in aniline) reduces basicity.

The amino group participates in a range of reactions. It can form imines (Schiff bases) with aldehydes or ketones, and it readily undergoes acylation and alkylation. In peptide and polymer chemistry, amino groups are often protected with groups such as Boc or Fmoc to control reactivity during synthesis. Biologically, amino groups are essential in amino acids, where they enable peptide bond formation and contribute to the properties of proteins, neurotransmitters, and various drugs. The amino group also participates in hydrogen bonding and salt formation, influencing solubility and reactivity.