A<unk>  molecule consists of a catechol structure (a benzene ring with two hydroxyl side groups) with one amine group attached via an ethyl chain. As such,<unk>  is the simplest possible catecholamine, a family that also includes the neurotransmitters norepinephrine and epinephrine. The presence of a benzene ring with this amine attachment makes it a substituted phenethylamine, a family that includes numerous psychoactive drugs. Like most amines,<unk>  is an organic base. As a base, it is generally protonated in acidic environments (in an acid-base reaction). The protonated form is highly water-soluble and relatively stable, but can become oxidized if exposed to oxygen or other oxidants. In basic environments,<unk>  is not protonated. In this free base form, it is less water-soluble and also more highly reactive. Because of the increased stability and water-solubility of the protonated form,<unk>  is supplied for chemical or pharmaceutical use as<unk>  hydrochloride—that is, the hydrochloride salt that is created when<unk>  is combined with hydrochloric acid. In dry form,<unk>  hydrochloride is a fine powder which is white to yellow in color.
Dopamine
Octopamine
Norepinephrine
Norepinephrine 
Catecholamine
Synephrine
Beta-Endorphin
Prolactin-releasing peptide