NH2grupp

NH2grupp, also called the amino group, is a functional group consisting of a nitrogen atom bonded to two hydrogen atoms and to the rest of the molecule (R-NH2). It is the defining feature of primary amines and is among the most common nitrogen-containing functional groups in organic chemistry.

In organic molecules the NH2 group is typically attached to a carbon skeleton. In amino acids, for example, the group appears as H2N-CHR-COOH. At physiological pH the amino group is protonated to NH3+, giving the characteristic zwitterionic form of amino acids and contributing to their solubility and reactivity.

Properties and reactivity: The lone pair on nitrogen makes the NH2 group basic and a good nucleophile. In water, typical amines have pKa values for their conjugate acids around 9–11, so at neutral pH the majority exists as NH3+. The group can participate in many transformations, including acylation to form amides, alkylation to give secondary or tertiary amines, and condensation with aldehydes or ketones to give imines (Schiff bases) or via reductive amination to primary amines.

Biological and practical significance: Amino groups are essential in biology, most notably in amino acids and proteins, where they act as both bases and sites of hydrogen bonding. They are also widely used in synthesis and materials chemistry, for example in protecting group strategies, polymerization, and as reactive handles for coupling reactions.