uhtulf - 2-9-2014 at 07:54
Greetings.
I'm really sorry to bother you with this, you probably have enough of this stuff.
I could use some help crystallizing some product.
I tried the Nitroaldol Reaction with substituted benzaldehydes by using the "Mix It Together And Let It Stand Somewhere" method.
First I tried 4-Fuoro-Benzaldehyde and Nitroethane.
20 g of the Benzaldehyde and 13 g of Nitroethane were mixed together, cooled and 1.5 g of Cyclohexylamine were added drop-wise to the solution. A
white smoke emerged from the liquid, which turned light transparent yellow shortly after. The mixture was left to stand in a dark place at ambient
temperature. After a few days droplets of water formed, after about ten days, neon yellow prisms precipitated from the solution. After three weeks the
orange mixture was filtered and the yellow precipitate recrystallized twice from boiling 98 % IPA which yielded 18.41 grams (63 % of theory) of
1-(4-Fuorophenyl)- Nitropropene as neon yellow prismatic needles.
Now, I tried to do this in the same way with 4-Ethylbenzaldehyde. The water separated, but it did not form a layer, as it did with the
Fluoro-analogue. Tiny droplets are dispersed in the orange mixture. Nothing crystallizes. It is now standing more than six weeks.
What could be the matter with this?
I tried scratching, cooling, putting samples of the mixture in different solvents (DCM, EtOH, IPA, MeOH: Everything dissolves; Acetic acid: Two
layers form, a light yellow upper and the orange lower layer).
I tried distilling off the water and drying samples of the mixture, which yields a dark red flowery smelling oil, no crystals.
Anyone having any good ideas?
Thanks in advance.
The Ethylbenzaldehyde is >97 % pure, stabilized with Tocopherol, the Nitroethane is distilled and the same as used in the former reaction, the
Cyclohexylamine as well.