1.3. Chemically speaking, what is caffeine?
Description
This article is from the Coffee and Caffeine FAQ, by Alex Lopez-Ortiz with numerous contributions by others.
1.3. Chemically speaking, what is caffeine?
Caffeine is an alkaloid. There are numerous compounds called
alkaloids, among them we have the methylxanthines, with three
distinguished compounds: caffeine, theophylline, and theobromine,
found in cola nuts, coffee, tea, cacao beans, mate and other plants.
These compounds have different biochemical effects, and are present in
different ratios in the different plant sources. These compounds are
very similar and differ only by the presence of methyl groups in two
positions of the chemical structure. They are easily oxidized to uric
acid and other methyluric acids which are also similar in chemical
structure.
Caffeine:
Sources: Coffee, tea, cola nuts, mate, guarana.
Effects: Stimulant of central nervous system, cardiac muscle, and
respiratory system, diuretic Delays fatigue.
Theophylline:
Sources: Tea
Effects: Cariac stimulant, smooth muscle relaxant, diuretic,
vasodilator
Theobromine:
Sources: Principle alkaloid of the cocoa bean (1.5-3%) Cola nuts and
tea
Effects: Diuretic, smooth muscle relaxant, cardiac stimulant,
vasodilator.
(Info from Merck Index)
The presence of the other alkaloids in colas and tea may explain why
these sometimes have a stronger kick than coffee. Colas, which have
lower caffeine contents than coffee are, reportedly, sometimes more
active. Tea seems the strongest for some. Coffee seems more lasting
for mental alertness and offers fewer jitters than the others.
A search in CAS and produced these names and synonyms:
RN 58-08-2 REGISTRY CN 1H-Purine-2,6-dione, 3,7-dihydro-1,3,7-trimethyl- (9CI) (CA INDEX NAME) OTHER CA INDEX NAMES: CN Caffeine (8CI) OTHER NAMES: CN 1,3,7-Trimethyl-2,6-dioxopurine CN 1,3,7-Trimethylxanthine CN 7-Methyltheophylline CN Alert-Pep CN Cafeina CN Caffein CN Cafipel CN Guaranine CN Koffein CN Mateina CN Methyltheobromine CN No-Doz CN Refresh'n CN Stim CN Thein CN Theine CN Tri-Aqua MF C8 H10 N4 O2
The correct name is the first one,
1H-Purine-2,6-diione,3,7-dihydro-1,3,7-trimethyl- (This is the
"inverted name") The "uninverted name" is
3,7-Dihydro-1,3,7-trimethyl-1H-purine-2,6-dione
Merck Index excerpt...
Caffeine: 3,7-dihydro- 1,3,7-trimethyl- 1H-purine-
2,6-dione; 1,3,7-trimethylxanthine; 1,3,7-trimethyl-
2,6-dioxopurine; coffeine; thein; guaranine;
methyltheobromine; No-Doz.
C8H10N4O2; mol wt 194.19. C 49.48%, H 5.19%, N 28.85%, O
16.48%.
Occurs in tea, coffee, mate leaves; also in guarana paste
and cola nuts: Shuman, U.S. pat. 2,508,545 (1950 to General
Foods). Obtained as a by-product from the manuf of
caffeine-free coffee: Barch, U.S. pat. 2,817,588 (1957 to
Standard Brands); Nutting, U.S. pat. 2,802,739 (1957 to Hill
Bros. Coffee); Adler, Earle, U.S. pat. 2,933,395 (1960 to
General Foods).
Crystal structure: Sutor, Acta Cryst. 11, 453, (1958).
Synthesis: Fischer, Ach, Ber. 28, 2473, 3135 (1895); Gepner,
Kreps, J. Gen. Chem. USSR 16, 179 (1946); Bredereck et al.,
Ber. 83, 201 (1950); Crippa, Crippa, Farmaco Ed. Sci. 10,
616 (1955); Swidinsky, Baizer, U.S. pats. 2,785,162 and
2,785,163 (1957 to Quinine Chem. Works); Bredereck,
Gotsmann, Ber. 95, 1902 (1962).
Hexagonal prisms by sublimation, mp 238 C. Sublimes 178 C.
Fast sublimation is obtained at 160-165 C under 1mm press.
at 5 mm distance. d 1.23. Kb at 19 C: 0.7 x 10^(-14). Ka at
25 C: <1.0 x 10^(-14). pH of 1% soln 6.9. Aq solns of
caffeine salts dissociate quickly. Absorption spectrum:
Hartley, J. Chem. Soc. 87, 1802 (1905). One gram dissolves
in 46 ml water, 5.5 ml water at 80 C, 1.5 ml boiling water,
66 ml alcohol, 22 ml alcohol at 60 C, 50 ml acetone, 5.5 ml
chloroform, 530 ml ether, 100 ml benzene, 22 ml boiling
benzene. Freely sol in pyrrole; in tetrahydrofuran contg
about 4% water; also sol in ethyl acetate; slightly in petr
ether. Soly in water is increased by alkali benzoates,
cinnamates, citrates, or salicylates.
Monohydrate, felted needles, contg 8.5% H2O. Efflorescent in
air; complete dehydration takes place at 80 C. LD50 orally
in rats: 200 mg/kg.
Acetate, C8H10N4O2.(CH3COOH)2, granules or powder; acetic
acid odor; acid reaction. Loses acetic acid on exposure to
air. Soluble in water or alcohol with hydrolysis into
caffeine and acetic acid. Keep well stoppered.
Hydrochloride dihydrate, C8H10N4O2.HCl.2H2O, crystals, dec
80-100 C with loss of water and HCl. Sol in water and in
alcohol with dec.
Therap Cat: Central stimulant.
Therap Cat (Vet): Has been used as a cardiac and respiratory
stimulant and as a diuretic.
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