2. • Chief alkaloid of tobacco plant (Nicotina tabacum)
• Occurs in the plant leaves as salt of malic acid and citric acid
to the extent of 4 to 5 percent.
• Named after the Frenchman Nicot who introduced tobacco in
France in 1560.
3. Isolation of Nicotine
Finely powdwred of tobacco plant
extract with dilute acid
remove cellulose, chlorophyll etc
Water soluble salts of alkaloids
made basic with lime or sodium hydroxide
remove water-soluble nonvolatile materials
acidified to about pH3 with solid oxalic acid
concentrated to a syrup
Crystalline nicotine oxalate
transferred to a separating funnel
treated with excess of aqueous KOH
Nicotine rises to the surface as brown oil
Extract with ether solution
4. Isolation of Nicotine
1. Waste part of the tobacco plant are finely powdwred and extacted
with dilute acid The water soluble salts of alkaloids are thus removed
in solution from cellulose, chlorophyll etc.
2. The acid extract is then made basic with lime or sodium hydroxide,
and steam distilled. Steam-distillation separates the nicotine from
water-soluble nonvolatile materials (sugars, inorganic salts etc)
3. The distillate is acidified to about pH3 with solid oxalic acid and
concentrated to a syrup. On cooling, the crystalline salt of nicotine
and oxalic acid separates.
4. The crystalline nicotine oxalate is then transferred to a separating
funnel and treated with excess of aqueous KOH. The nicotine thus set
free rises to the surface as a brown oil and separated by extraction
5. The ethereal solution of the alkaloid is dried and the ether
evaporated. For further purification the residue is fractionally distilled
5. Properties of Nicotine
1. It exists in a liquid form.
2. It is colourless.
3. The boiling point is 246° C
4. It has a tobacco like smell.
5. It is soluble in water and also in organic solvents such as ethanol,
ether and benzene.
6. It is a deadly poison to animals.
7. In small quantities, nicotine stimulate the nervous system for a
while. A low nicotine content tobacco is used for smoking
6. Structure of Nicotine
1. Elemental analysis and molecular weight determination leads to
the molecular formula C10H14N2 for nicotine.
2. It absorbs two molecules of CH3I, suggesting the tertiary nature of
both the nitrogen atoms.
3. On oxidation with chromic acid, nicotine yields nicotinic acid.
This shows that the alkaloid contains a pyridine nucleus with a side
chain at 3-position.
7. Structure of Nicotine
Therefore the formula of nicotine may be written as,
4. Nature and position of the side chain:
i.The alkaloid forms an additional compound with zinc chloride, which
then heated with lime yields pyridine, pyrrole and methylamine.
This suggests that the side chain C5H10N is pyrrole derivative.
8. Structure of Nicotine
ii. When heated with concentrate HCl at 200-300°C, nicotine yields
CH3I, showing that methyl group is attached to N-atom.
iii. Nicotine hydriodide when treated with CH3I, forms nicotine
isomethiodide which on oxidation with potassium ferricyanide yields
nicotone. This on further oxidation with chromium trioxide produces
9. Structure of Nicotine
The formation of hygrinic acid proves the N-methylpyrrolidine is
attached to the pyridine nucleus through C2.
5. From the above consideration the structural of nicotine may be
6. The above structure of nicotine is confirmed by following reaction
i. Nicotine when treated with bromine in acetic acid followed by
sulphurous acid gives dibromonicotine. This upon oxidation with a
mixture of sulphurous acid and sulphuric acid yields 3-acetylpyridine,
oxalic acid and methylamine.
10. Structure of Nicotine
ii. Nicotine on reaction with bromine in hydrobromic acid gives
dibromonicotine which when heated with barium hydroxide solution
at 100°C, yiels nicotinic acid, malonic acid and methylamine.