linguistic:paraphrasing
Chemistry

Nicotine is a hygroscopic, colorless to yellow-brown, oily liquid, that is readily soluble in alcohol, ether or light petroleum. It is miscible with water in its neutral amine base form between 60 °C and 210 °C. It is a dibasic nitrogenous base, having K =1×10, K =1×10. It readily forms ammonium salts with acids that are usually solid and water-soluble. Its flash point is 95 °C and its auto-ignition temperature is 244 °C. Nicotine is readily volatile (vapor pressure 5.5 Pa at 25 °C) On exposure to ultraviolet light or various oxidizing agents, nicotine is converted to nicotine oxide, nicotinic acid (niacin, vitamin B3), and methylamine.

Nicotine is chiral and hence optically active, having two enantiomeric forms. The naturally occurring form of nicotine is levorotatory with a specific rotation of =–166.4° ((−)-nicotine). The dextrorotatory form, (+)-nicotine is physiologically less active than (−)-nicotine. (−)-nicotine is more toxic than (+)-nicotine. The salts of (−)-nicotine are usually dextrorotatory; this conversion between levorotatory and dextrorotatory upon protonation is common among alkaloids. The hydrochloride and sulfate salts become optically inactive if heated in a closed vessel above 180 °C. Anabasine is a structural isomer of nicotine, as both compounds have the molecular formula C H N.

Nicotine that is found in natural tobacco is primarily (99%) the S-enantiomer. Conversely, the most common chemistry synthetic methods for generating nicotine yields a product that is approximately equal proportions of the S- and R-enantiomers. This suggests that tobacco-derived and synthetic nicotine can be determined by measuring the ratio of the two different enantiomers, although means exist for adjusting the relative levels of the enantiomers or performing a synthesis that only leads to the S-enantiomer. There is limited data on the relative physiological effects of these two enantiomers, especially in people. However, the studies to date indicate that (S)-nicotine is more potent than (R)-nicotine and (S)-nicotine causes stronger sensations or irritation than (R)-nicotine. Studies have not been adequate to determine the relative addictiveness of the two enantiomers in people.

Pod mod electronic cigarettes use nicotine in the form of a protonated nicotine, rather than free-base nicotine found in earlier generations.