Tobacco contains a variety of alkaloids. In addition to the main component nicotine (containing 2% to 8%), it also contains demethylnicotine (nornicotine), pseudoequisetine (neonicotine) and at least seven A trace amount of alkaloids. Nicotine is a nitrogenous base composed of two heterocyclic compounds, pyridine and pyrrole. The pure product is a colorless oily liquid with a boiling point of 246°C. It has optical rotation (left-handed rotation) and is soluble in water and many organic solvents.
Nicotine often exists in plants as salts with organic acids such as citric acid and malic acid. During extraction, tobacco can often be heated with an inorganic strong acid solution and then neutralized with alkali to free nicotine. Then it is extracted with an organic solvent, and the solvent is evaporated to obtain nicotine. Because of its volatility, it can be extracted by steam distillation.
In addition, because nicotine is a liquid, it is difficult to separate and purify. Therefore, nicotine is often reacted with picric acid to form nicotine dipicric acid salt crystals for easy handling.