nnn is a derivative of nicotine that is produced in the curing of tobacco, in the burning of tobacco (such as with cigarettes), and in the acidic conditions of the stomach. nicotine is converted into nornicotine via nicotine n-demethylase (nnd), an enzyme found in the tobacco plant that works by removing the methyl group from the nitrogen on the 5-membered ring of nicotine. from there, nornicotine undergoes nitrosation (the conversion of organic compounds into nitroso derivatives by gaining a nitrosonium (n=o) group) on that same nitrogen, converting it to nnn.