Caffeine

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Caffeine
Names
IUPAC name
1,3,7-Trimethylpurine-2,6-dione
Other names
1,3,7-Trimethylxanthine
Guaranine
Methyltheobromine
Theine
Properties
C8H10N4O2
Molar mass 194.19 g/mol
Appearance White solid
Odor Odorless
Density 1.23 g/cm3
Melting point 235–238 °C (455–460 °F; 508–511 K)
Boiling point 178 °C (352 °F; 451 K) (sublimes)
2.17 g/100 ml (25 °C)
20.0 g/100 ml (80 °C)
66.6 g/100 ml (100 °C)[1]
Solubility Soluble in ethyl acetate, pyridine, pyrrole, THF
Slightly soluble in ethanol, petroleum ether
Solubility in acetone 2 g/100 ml[2]
Solubility in benzene 1 g/100 ml
Solubility in chloroform 18.2 g/100 ml
Solubility in diethyl ether 0.2 g/100 ml
Solubility in ethanol 1.5 g/100 ml
Vapor pressure 9·10-7 mm Hg at 25 °C
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
127 mg/kg (mouse, oral)
367.7 mg/kg (rat, oral)
Related compounds
Related compounds
Theobromine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Caffeine is an organic chemical compound, an alkaloid, of the methylxanthine class. It is widely used as central nervous system (CNS) stimulant, in the form of coffee.

Properties

Chemical

Caffeine reacts with acids to give salts of caffeine. Reaction with citric acid will give caffeine citrate.

Physical

Caffeine is an odorless white solid, slightly soluble in water, though its solubility increases with temperature and the addition of an acid. It shows good solubility in dichloromethane and chloroform.

Availability

Caffeine is available as pills in most pharmacies and drugstores.

Caffeine is more readily available in the form of coffee.

Preparation and isolation

It's not economical to make caffeine from precursors. Extracting it from readily available sources is the only economical way to get useful amounts.

Extraction from caffeine pills

Crush a desired amount of caffeine pills in a mortar until they are turned into a fine powder. The fine powder is then transferred into a flask or beaker. To the powder from the beaker, a volume of dichloromethane is added and the suspensions is stirred for a few minutes. The suspension is left to decant, then filtered using a fritted funnel (or funnel with a proper filter paper), to remove the solid. The filtrate is transferred in a round bottom flask, which is connected to a distillation setup or a rotary evaporator to remove and recover the DCM via distillation. After all the DCM has been removed from the flask, it is transferred in another beaker, where hot water is added until it completely dissolves. The solution is cooled to recrystallize the caffeine. The crude caffeine crystals are filtered using a filter paper or fritted funnel and dried. The crude caffeine can be further purified via sublimation. A good procedure can be found here.

Extraction from coffee

Similar to above, though the yields are much lower. NileRed made a video on this process.

Projects

  • Make caffeine salts

Handling

Safety

Caffeine, as found in coffee and tea, has stimulant effects when consumed. Side effects include elevated blood pressure, restlessness, insomnia, headaches. Caffeine overdose can result in a state of central nervous system over-stimulation called caffeine intoxication.

Storage

Caffeine should be kept in plastic or glass bottles, away from light and corrosive fumes.

Disposal

No special disposal is required.

References

  1. https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Product_Information_Sheet/c0750pis.pdf
  2. O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Cambridge, UK: Royal Society of Chemistry, 2013., p. 289

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