09-04-04 17:02
No 529552
in the synthesis of phenyl-2-nitropropene via nitroethane/benzaldehyd/n-butylamine is frequently a solvent (toluene) used.
what is the reason for the use of a solvent?
swim found some threads where p2np is produced with good succes without any solvent.
and at last: when toluene is used, must this distilled off before crystallization or is this not necessary ?
yes, swim utfse, but there is no uniform opinion.
thx
(Chief Bee)
09-05-04 22:45
No 529729
what is the reason for the use of a solvent?
To be able to speed up the reaction by heating it and to continuously distill off the water formed in the reaction.
Heating the reaction mixture without a solvent present would likely overheat the product.
when toluene is used, must this distilled off before crystallization or is this not necessary?
If the reaction mixture is cooled in the fridge before filtering, most of the product will precipitate even in the presence of the solvent.
(At least as long as you don't use larger amounts than suggested in the literature methods (../rhodium /phenyl
The Hive - Clandestine Chemists Without Borders
(Newbee)
09-13-04 21:07
No 531165
swid did two attempts:
1. 100ml EtOH
101ml BA
79ml NE
20ml n-But.amin
refluxed 2 hours at 83° C.
Result: one layer of red/orange layer. Put this in
the freezer: milky white upper layer appeared and
sucked away.
orange/red layer cooled again down to -10°C and then
swirled to bring it in contact with air:
the whole mass crystallized in a few seconds.
re-X with IPA gave a beaker full of near white
sparkling beauties
2. no solvent was used
49 ml BA
38 ml NE
6 ml n-Butyla.
refluxed for 2 hours at 100°C
result: water layer over a deep orange oil layer.
water drained away with sep. funnel.
oil cooled again to -10°C, swirled to bring it in
contact with air and -again- the whole shebang
crystallized in a few seconds.
> re-X with IPA > some result as in the first attempt
yield is over 80% in 1. + 2.
the trick is: to cool it down in the freezer and then swirl it with a glas rod to bring air in the oil.
dean-stark trap was not necessary
greez
09-22-04 13:14
(Rated as: insignificant)