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Title: Phenylethylamine  
Author: World Heritage Encyclopedia
Language: English
Subject: Alkaloid, Monoamine neurotransmitter, Psilocybe semilanceata, Vesicular monoamine transporter, PEA, Substituted methylenedioxyphenethylamines, Releasing agent
Publisher: World Heritage Encyclopedia


Not to be confused with 1-phenylethylamine.


Phenethylamine /fɛnˈɛθəlɒˈmn/ (PEA), β-phenethylamine, or phenylethylamine is an organic compound and a natural monoamine alkaloid, a trace amine, and also the name of a class of chemicals with many members well known for psychoactive drug and stimulant effects.[1] Phenylethylamine functions as a neuromodulator or neurotransmitter in the mammalian central nervous system.[2] It is biosynthesized from the amino acid phenylalanine by enzymatic decarboxylation. In addition to its presence in mammals, phenethylamine is found in many other organisms and foods, such as chocolate, especially after microbial fermentation. It is sold as a dietary supplement for purported mood and weight loss-related therapeutic benefits; however, orally ingested phenethylamine is usually inactive because of extensive first-pass metabolism by monoamine oxidase (MAO) into phenylacetic acid. This prevents significant concentrations from reaching the brain.[3][4]

The group of phenethylamine derivatives is referred to as the phenethylamines. Substituted phenethylamines, substituted amphetamines, and substituted methylenedioxyphenethylamines (MDxx) are a series of broad and diverse classes of compounds derived from phenethylamine that include stimulants, psychedelics, and entactogens, as well as anorectics, bronchodilators, decongestants, and antidepressants, among others.


Phenethylamine is widely distributed throughout the plant kingdom.[5]


Phenethylamine is a primary amine, the amino-group being attached to a benzene ring through a two-carbon, or ethyl group. It is a colorless liquid at room temperature. Phenethylamine is soluble in water, ethanol, and ether. Similar to other low-molecular-weight amines, it has a fishy odor. Upon exposure to air, it forms a solid carbonate salt with carbon dioxide. Phenethylamine is strongly basic, pKb = 4.17 (or pKa = 9.83), as measured using the HCl salt,[6] and forms a stable crystalline hydrochloride salt with a melting point of 217°C. Phenethylamine is also a skin irritant and possible sensitizer. Its density is 0.962 g/ml.


One method for preparing β-phenethylamine, set forth in J. C. Robinson's and H. R. Snyder's Organic Syntheses (published 1955), involves the reduction of benzyl cyanide with hydrogen in liquid ammonia, in the presence of a Raney-Nickel catalyst, at a temperature of 130°C and a pressure of 13.8 MPa. Alternative syntheses are outlined in the footnotes to this preparation.[7]

A much more convenient method for the synthesis of β-phenethylamine is the reduction of ω-nitrostyrene by lithium aluminum hydride in ether, whose successful execution was first reported by R. F. Nystrom and W. G. Brown in 1948.[8]


Phenethylamine, similar to amphetamine in its action, releases norepinephrine and dopamine.[9][10][11] When taken orally, though, it is rapidly metabolized.[12]

Abnormally low concentrations of endogenous phenethylamine are found in those suffering from attention-deficit hyperactivity disorder (ADHD),[13] whereas abnormally high concentrations have been discovered to have a strong, positive correlation with the incidence of schizophrenia.[14]


Phenylethylamine's half-life is 5 to 10 minutes.[15] It is metabolized by phenylethanolamine N-methyltransferase,[16] MAOA,[4] MAOB,[3] aldehyde dehydrogenase, and dopamine-beta-hydroxylase.[15] N-methylphenethylamine, an isomer of amphetamine, is produced when phenethylamine is used as a substrate by phenylethanolamine N-methyltransferase.[16][17] When the initial phenylethylamine brain concentration is low, brain levels can be increased 1000-fold when taking an MAO inhibitor (MAOI), and by 3-4 times when the initial concentration is high.[18]


Acute toxicity studies on phenethylamine show an LD50 = 100 mg/kg, after intravenous administration to mice.[19]

See also


External links

  • Book II of PiHKAL online
  • Phenethylamine entry in PiHKAL • info
  • Review and summary of PiHKAL, including table of 300+ phenethylamines: postscript
  • A Structural Tour of PiHKAL


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