Newsgroup: it.scienza.chimica
Titolo: Sintesi del Piperonale

Qualcuno ha idea su dove cercare per sintetizzare la suddetta aldeide
profumata ?

 ha scritto nel messaggio 
news:m4eed6hgskung0mtd...@4ax.com...
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ma è attendibile questa sintesi, specie da un sito come quello.
 Poi anzichè partire dal 3,4 metilendiossibenzene non sarebbe meglio
partire da composti piu' simili come la vanillina?
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>attrezzato, università...)
Ciao
Tex 

Ripropongo:
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risorse free e a pagamento, laboratorio attrezzato dell'universita'

 risorse free e a pagamento, laboratorio attrezzato dell'universita'
Le informazioni contenute su Rhodium.ws sono estremamente
attendibili.
Se le risorse sono free e sei all'università, perchè non comprare
questa aldeide direttamente:
http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=it&N4=W291102|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC
dal sito sigma-aldrich americano 1 Kg = 90$. Quello italiano non dà il
prezzo, ma sarà cmq simile.
Pertendo dalla vanillina, sempre su 
rhodium.ws
:
Piperonal From Vanillin
Vanillin can be used to synthesize piperonal. The route is vanillin →
protocatechualdehyde → piperonal. Vanillin's methyl ether is cleaved
and then the protocatechualdehyde is methylenated to piperonal.
Vanillin is the flavor of vanilla. The extracts from the store are
quite watered down and normally expensive. Sometimes one can find
large bottles of extract cheap. Large flavoring companies would
probably be glad to sell you a heap of the pure stuff.
Vanillin's methyl ether is difficult to cleave under the conditions
normally employed for demethylation according to Robert Lange[30].
Lange cites references to this fact referring to their low yields
(less than 50%) when using such reagents as dilute HCl, HBr,
phosphorus pentachloride, aluminum chloride in benzene. No mention of
the use of aluminum chloride in chlorobenzene was given as is cited
for possible use with demethylation of eugenol. That method may be
worthy and should be tested. Reference was given to the first high
yielding method by using aluminum bromide in nitrobenzene to yield 93%
of protocatechualdehyde from vanillin. Lange goes on to present his
demethylation procedure of vanillin with aluminum chloride, and
pyridine in methylene chloride as solvent. Pyridine is a very hot
chemical and is best avoided so I refer you to the original reference
for the details. The procedure given there is easy enough to follow.
Pearl and Beyer[31] report on the method of aluminum bromide in
nitrobenzene for demethylation of vanilla as follows:
In a fume hood. A solution of 15.2 g (0.1 mole) of vanilla in 45 ml of
nitrobenzene at 15°C is treated with a solution of 53.4 g of anhydrous
aluminum bromide in 60ml of nitrobenzene. 125 ml of nitrobenzene are
added to the gel which forms with stirring. (do not breath
nitrobenzene vapors or let contact with skin. If contact occurs flush
area with water for 15 min.) Heat solution to 95°C and then let cool
to room temperature. Allow to stand at room temperature for 30
minutes. The dark mixture is cooled and added to IL of water
containing a little HCl. The mixture is extracted with ether and the
ether is then extracted with 5% sodium hydroxide solution. The
hydroxide solution is washed with ether and then acidified with dilute
sulfuric acid. The acidic solution is extracted with ether, dried, and
then distilled off to leave 12.8 g of protocatechualdehyde.
Methylenate this with the procedure listed in the safrole section
replacing the 4-allyl catechol with 138 g of protocatechualdehyde.
Hayashi and Namura[32] discuss demethylation during the pulping
process and conducted experiments on individual components under such
conditions. Eugenol and vanillin were both demethylated by cooking
with either 5% NaOH or 5% Na2SO4, 1% NaHCO3 and H2O. The degree of
demethylation is not given in the abstract but it is in the paper
which luckily is in English if one cares to look it up. The reaction
does proceed slowly.
http://www.erowid.org/archive/rhodium/chemistry/tcboe/chapter5.html
Domandare è lecito, rispondere è cortesia. Che cosa ci devi fare con
la 3,4-metilendiossibenzaldeide?
Io, alla tua domanda, ho riposto...
Ciao
mr.kite

mr.kite

 Ciao
Ciao