Question

synthesis of nicotine

Answer 1

Nicotine is a potent parasympathomimeticstimulant and an alkaloid found in thenightshade family of plants.[4] Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs),[5][6] except at two nicotinic receptor subunits (nAChRα9and nAChRα10) where it acts as a receptor antagonist.[5] Nicotine is found in the leaves of Nicotiana rustica, in amounts of 2–14%; in the tobacco plant, Nicotiana tabacum; inDuboisia hopwoodii; and in Asclepias 

Answer 2

Nicotine is a molecule, alkaloid, naturally produced by some Solanaceae.
The brownish coloration of liquid nicotine is a natural process that is produced upon exposure to light, heat and oxygen.
The liquid, when freshly synthesized is colourless, so is the nicotine extracted from tobacco leaves, after purification