Explain, using chemical structures, how the discovery of heroin is related to the discovery of aspirin. Draw the structures of heroin and aspirin, and the reactions that produced them.

Using chemical structures, explain why heroin crosses the blood brain barrier more readily than does morphine. Explain why this is believed to be related to its addictive potential. Is heroin a potent agonist of the mu receptor? If not, how does it produce its effect after it enters the central nervous system?