2 mole benzaldehyde
2.1 mole nitroethane
80ml IPA 99%+
16g n-butylamine* see note
the 2l flask was charged with the above contents and swirled without splashing briefly.
Then placed in an oil bath to 75-80c.
After 6+ hours the solution began to change colour. yellow -going- orange
Coinciding with the colour change was the formation of a water layer.
heat was reduced 40-45c until the water layer appeared to have reached theory.
@ 10 hours in theory appeared to have been reached (later it was measured and established to have been exceeded by a few ml ~ perhaps excess catalyst was the reason and reaction wasnt quite 100% complete)
solution allowed to cool to rt. placed in fridge overnight, then freezer 24 hours.
1st yield 224g of very nice yellow crystals,(mp high 50sc) light washed and performed well in subsequent reaction 83-94% yields without recrystallisation.
The carefully filtered mother solution now gave off a scent of benzaldehyde. All was heated gently again 40c ish and separation/crystallisation repeated.
Another 34g of good quality slight orange crystal formed and was processed.
No smell of benzaldehyde remained. a slight burning sharp to the eyes ~ like someone blowing something minty in your eyes.
Dude didnt see the point in repeating a heat then freeze. instead he separated the catalyst/water layer, set it aside.
The now deep orange mother solution he added a capful or two of meoh**, froze then seeded.
a solid formed what didnt look promising, however upon removing and recrystillising twice, another 11g of needle crystals orange was obtained.
total yield 269g believe it or not theres still some p2np crystallised out the mother solution not included in the total.. after leaving for several weeks in the freezer it fell out the solution.
Note*: the 16g n-butylamine was a mistake, 16ml was the intended amount to use.(still a lot i know)
** meoh was added at that point after reading byproducts was more soluble than the p2np, it made sense to me at that point it may induce more p2np to precipitate out.
Thanks fishinabottle for a informative post on another forum regarding temps of said reaction. It kept this experiment clean and easy to work up producing excellant quality results
pseudo science thought, it appears introducing air into the solution when filtering forms byproducts? i was careful to avoid splashing and covered the funnel when filtering relying on suction pressure rather than airflow.
In the past the filtering point has changed the orange solution too deep red and ive been unable to recover more product, or if so its been a nightmarish scenario for a few more gs.
Theres better more efficient methods on this thread, but in the spirit of things theres nothing like sharing practical experience/results.