Phenethylamine (phenyl-ethyl-amine): A phenyl ring, connected to an amine by an ethyl chain.
Phenethylamine is present in our nervous system, and is also the backbone of many psychoactive compounds including the neurotransmitters dopamine and norepinephrine and psychedelic compounds investigated by Shulgin in PiHKAL. It is sold as a nutritional supplement with stimulant effects as it acts as releaser of norepinephrine and dopamine in the brain, but is largely inactive due to extensive first-pass metabolism when taken orally ensuring very little passes the blood-brain barrier.
Amphetamine (alpha-methyl-phenethylamine): Phenethylamine methylated at the alpha carbon, the carbon closest to the functional amine group.
Amphetamine was first synthesized in 1887 by Lazăr Edeleanu as part of a series of compounds related to the herbal stimulant ephedrine. It rapidly increases the concentrations of dopamine, serotonin, and norepinephrine in the brain and has powerful motivating and euphoric effects. It has been used since its discovery to increase concentration and alertness, including World War II where British troops alone used 72 million amphetamine pills and today where Adderall is prescribed to children and adults diagnosed with ADHD.
Why is the line representing the methyl group wiggly instead of straight like you may be used to? Well, there are two possible stereoisomers of amphetamine that can be visualized more easily in 3D.
We can think of these as right and left handed versions – while they look identical at a glance, if we investigate their structure we cannot make them line up with each other no matter how much we rotate them around. We can think of the wiggly line as a methyl group coming out of, or going into, the page depending on the stereoisomer.