Hjalmar_Poelzig - 2-7-2004 at 03:39
There is an article from Bull. Soc. Chim. Fr. from the 1960s that claims 100% yield from the decarboxylation of tryptophan.
I don't have the complete ref now but will post it asap. No experimental part is given, but it is part of a large review of the decarboxylation
of alpha-amino acids.
Now, have a look at this patent:
http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=GB1008594
It is somewhat similar, except that yields are lower and substituted aceto/benzophenones are used.
My experiments with Trp/acetophenone heated 4 hours at 130°C like in the paper, gave always a miniscule yield or none at all, accompagnied with a
huge ball of tar. Also, no acetophenone could be recovered from the rxn mixture although a 4x molar excess was used.
All other attempts (DMSO, turpentine+d-carvone) to decarboxylate tryptophan also gave chiefly tar and unreacted precursor.
The acetophenone rxn is nice in its way that, you can infact see the decarboxylation happening, CO2 starts evolving around 125°C. But it is far from
over after 4 hours, then the crackling and bubbling even seem to increase. Yet tar is always the chief product.
This is what was done:
Heat 1 mol tryptophan w 4 mol acetophenone at 130-140 °C for 4 hours. What happens is that an unstable ketimine is formed, which loses CO2 to become
the ketimine of tryptamine, which is quite stable. Therefore, this is heated for 1-2 hours with an equimolar amount of 10% ethanolic KOH, cooled and
acidified. Organic layer is removed, aq. layer washed with solvent, then everything is brought to pH 7 with NaHCO3 and the dirty stuff that
precipitates is washed away with DCM.
Then basified with ammonia to precipitate the tryptamine. Yield was at most 2 gr from a 30 gr run.
I begin to think that tryptamine has something personal against me 
Organikum - 2-7-2004 at 12:00
These test-tube dacarboxylations are quite a nonsense. Decarboxylations are known to take place at elevated temperatures and pressure. Any small
gascylinder like those which come for CO2 bubblers "homemade softdrinks from syrup machines" like make a fine "bomb". Holding
elevated pressure with a minimum security marge of x8 (in europe at least) to burst pressure. And they will burst controlled open and never explode.
Leave enough headspace (1/2 volume is ok) and dont forget to purge the air out before use. CO2 is ok for this.
Numbers: A CO2 bottle is rated for 120atm max. This says the bottle wont burst open in a controlled way before 960atm. Thats the law. All european
manufacturers exceed laws requirements by at least 50%, you see, this stuff is good stuff.
I once got me this information for some other purposes, but it is checked and true.
ORG
many thanks!
Hjalmar_Poelzig - 5-7-2004 at 05:44
A very clever idea I must say! 
Looks like it is ideal as a general home pressure bomb.
I will get myself one of these next week and perform a small scale trial.
Report to follow 
almost forgot
Hjalmar_Poelzig - 5-7-2004 at 12:40
The reference for the tryptophan/acetophenone paper that claims the 100% yield I mentioned is:
Bull Soc Chim Fr (1964) p 2523 - 2532
If_6_was_9 - 6-7-2004 at 08:28
I think the first article here is it. Ripway.com has a 5 MB per day limit. Try again later if the links don't work.
http://home.ripway.com/2003-11/39191/LaDecarb/LaDecarbI.PDF 764 KB
http://home.ripway.com/2003-11/39191/LaDecarb/LaDecarbII.PDF 485KB