The difference between cocaine and crack cocaine is almost entirely one of pH, the relative scale of acidity or alkalinity. Regular cocaine in its original plant form, coca leaf, is commonly consumed by people across the mountainous parts of South America and has been for millennia, much as caffeine has been used through drinking tea in parts of Asia. It causes little to no harm; people can drink coca tea with no more impact than the caffeine from a soft drink.
But when you concentrate and tweak the compound just slightly to make it more alkaline (called “base” in chemistry), that increases its “stickiness,” the speed and tenacity with which it binds to blood and brain tissue (which is slightly more acidic), increasing the speed with which it’s transported to the nervous system and thus “hits” the user producing the cocaine “high.”
The more sudden and intense the “high,” the more addictive the substance. It’s why most American cigarette manufacturers add ammonia to tobacco: it changes the pH of nicotine and thus converts the nicotine in the cigarette from “normal nicotine” into free-base “crack
— source hartmannreport.com | Thom Hartmann | Oct 5, 2021