Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

CAFFEINE FKOM TEA 405
cools the argmme hydrochlonde is almost quantitatively precipitated
in sheaves of prisms which are recrystalhsed m the same way
Yield 7-8 g
rf-Arginine monohydrochlonde smters at 218° and decomposes
with copious frothing at 235°
The flavianic acid can be recovered from its sparingly soluble barium
salt as follows Decompose the salt with a slight excess of hot 20 per
cent sulphuric acid, filter at the pump while hot, add some concentrated
hydrochloric acid to the clear filtrate, and allow the free sulphonic acid
to crystallise
The method given by Bergmann 1 for the preparation of arginine
may also be recommended here
10 CAFFEINE FROM TEA
In the simplified extraction apparatus (Fig 27 on p 35) 100 g
of finely powdered tea or tea dust are extracted for eight hours with
400 c c of alcohol The alcoholic extract is then added to a suspension
of 50 g of magnesium oxide in 300 c c of water, and the whole
is evaporated to dryness on the steam bath m a porcelam basm
with frequent stirrmg The pulverulent residue is boiled once with
500 c c and then three times with 250 c c of water and filtered while
hot at the pump
After 50 c c of dilute sulphuric acid have been added to the
combined nitrates, they are concentrated to about one-third of their
volume, filtered if necessary while hot from the flocculent precipitate
which occasionally forms, and then extracted five times with 30 c.c
portions of chloroform
The pale yellow chloroform solution is decolorised by shaking,
first with a few cubic centimetres of sodium hydroxide solution, then
with the same volume of water, and is evaporated to dryness The
residue of crude caffeine is recrystallised from a little hot water
Yield 2 0-2 5 g. Soft, flexible, silky needles containing one molecule
of water of crystallisation
In the same way theobromme can be isolated from cocoa powder
which has previously been freed from fat with ether or petrol ether
in an extractor Prepare caffeine from the theobromme by methylation
according to the method of H Blitz 2
1 Z physiol Chem, 1926, 152, 293
2 Annalen, 1917, 413, 190 The reaction was first carried out by A Strecker
(Annalen, 1861, 118, 170)