How does the functional group affect the action of cocaine?

Cocaine is one of the most powerful addictive stimulant drugs known to mankind. It is produced from the leaves of the coca plant, which is commonly found in South America. Cocaine is a weakly alkaline chemical compound. There are various chemical forms of cocaine that are available, and depending on their functional groups, their properties are different. These forms are:
1) Cocaine hydrochloride, which is available in powder form and can be used intravenously or nasally. This form of cocaine is prepared by neutralizing the alkaline character of cocaine by using acids. The hydrochloride form is the most common, although sulfate and nitrate functional groups may also be added instead of hydrochloride. The presence of the hydrochloride group makes this form of cocaine water-soluble, which means it can be dissolved in water and used intravenously.
2) Freebase Cocaine—this form does not have the hydrochloride group in it and is typically prepared through neutralization of the salt group using an alkaline solution. Freebase cocaine is water-insoluble, unlike the hydrochloride form. This form of cocaine is usually smoked.
3) Crack Cocaine—this form of cocaine is produced by treatment of cocaine hydrochloride with ammonia or sodium bicarbonate and water, which is followed by heat treatment to remove the hydrochloride group. Crack cocaine is typically used by inhaling its vapors. Crack cocaine can be up to 100% pure cocaine and hence is the most lethal. It gives the user a "high" very quickly as it reaches the brain faster than the other forms and hence is also more likely to cause an overdose.
Freebase and crack cocaine are the more addictive forms of cocaine. And the lack of a hydrochloride group ensures that these forms are smoked, thus reaching the brain faster and giving the user the "high" sensation faster as compared to the hydrochloride form.
Thus, depending upon the presence of the functional group, cocaine forms can have different types of usage pathways (intravenously vs nasally vs smoking), can have different rates of effects (faster vs slower high), and may have more addictive effects than other forms.
Hope this helps.