Nicotine
Properties
| State | Liquid at room temperature (oily) |
| Color | Colorless to pale yellow (turns brown on air exposure) |
| Solubility | Miscible with water below 60 °C; also soluble in alcohol and ether |
| Melting Point | -79 °C |
| Boiling Point | 247 °C |
About Nicotine
Nicotine is a chiral pyridine-pyrrolidine alkaloid (formula C10H14N2, molar mass 162.232 g/mol) that the tobacco plant Nicotiana tabacum biosynthesizes in its roots and translocates to the leaves as a chemical defense — the molecule paralyzes the nervous system of insects feeding on the plant by overstimulating their acetylcholine receptors. The same mechanism that kills aphids works on humans, just at different doses: at the microgram-per-puff levels delivered by a cigarette, nicotine binds to nicotinic acetylcholine receptors (the α4β2 subtype is the high-affinity one in the brain), triggers dopamine release in the ventral tegmental area, and produces the alertness-and-relaxation profile that makes it among the most reinforcing drugs known. The pKa of the pyrrolidine nitrogen is 8.0, so at lung pH (~7.4) about 31% of inhaled nicotine is unprotonated and crosses alveolar membranes within seconds — the brain hit lands in 7–10 seconds, faster than IV heroin. Half-life in plasma is roughly 2 hours, which sets the dosing interval of cigarette smoking at about every 30–40 minutes. Nicotine itself is not classified as a carcinogen — the cancer in tobacco use comes from polycyclic aromatic hydrocarbons, nitrosamines, and benzene in combustion smoke — but it is the molecule that drives addiction. Industrially, nicotine inspired the neonicotinoid pesticide class (imidacloprid, clothianidin) and remains a research tool for nAChR pharmacology.
Where you'll encounter it
If you've ever opened a fresh nicotine patch (Nicoderm CQ delivers 7, 14, or 21 mg over 24 hours), the brown color of the drug reservoir is not the molecule — pure nicotine is colorless when fresh. The brown is oxidation products that form within hours of air exposure, which is why pharma-grade nicotine is shipped under nitrogen and why old vape cartridges turn dark and harsh-tasting. In a pharmacology lab, nicotine is the canonical agonist for studying nicotinic acetylcholine receptor subtype selectivity — radiolabeled [3H]-nicotine binding to brain membranes is how the α4β2 versus α7 subtype distribution gets mapped. The toxicology number that matters: liquid e-cigarette refills containing 18–36 mg/mL of nicotine have caused fatal pediatric ingestions, because a teaspoon of high-strength e-liquid contains roughly 100 mg — well above a lethal dose for a toddler.
Common Uses
- Active ingredient in transdermal patches (7-21 mg/24h), gums, lozenges, and inhalers for smoking cessation
- Pharmacological agonist for nicotinic acetylcholine receptor research in neuroscience and addiction studies
- Radiolabeled [3H]-nicotine binding probe for nAChR subtype mapping in brain tissue
- Active ingredient in e-liquid formulations for electronic cigarettes at 3-50 mg/mL
- Structural lead compound for the neonicotinoid pesticide class (imidacloprid, clothianidin)
- Historical agricultural insecticide (40% nicotine sulfate, 'Black Leaf 40'), banned in the U.S. in 2014
- Reference standard in forensic and clinical toxicology for cotinine metabolite assays
Safety Information
GHS classifications: H300 + H310 + H330 (fatal if swallowed, in contact with skin, or if inhaled), H411 (toxic to aquatic life with long-lasting effects). Nicotine is rapidly absorbed transdermally — the LD50 in adults is debated but lies somewhere between 0.5 and 1.0 g for chronic users, much lower (around 50 mg) in non-tolerant individuals; pediatric fatalities have occurred at under 10 mg. OSHA PEL is 0.5 mg/m3 (8-hour TWA, skin notation) for nicotine vapor. Handle pure nicotine with double nitrile gloves, lab coat, and in a fume hood — skin contact with concentrated material can cause systemic toxicity within minutes (nausea, vomiting, tachycardia, seizures). Liquid e-cigarette refills must be stored in child-resistant containers per the U.S. Child Nicotine Poisoning Prevention Act of 2015. Treat all nicotine waste as hazardous.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.