newbies
Harmless
Posts: 11
Registered: 21-1-2012
Member Is Offline
Mood: No Mood
|
|
Problem crystalising phenyl2nitropropene
Hello, I recently tried to do the synthesis of phenyl 2 nitropropene following this procedure:
- 17 ml benzaldehyde 99,9%
- 13,3 ml nitroethane 98%
- 3,3 ml n-butylamine 99,9%
- 30 ml toluene 99%
I mixed these chems in a round bottom flask and let it to reflux for 6 hours at 100•C with a Dean and stark trap to remove the water in the
reaction.
After i let the solution remain to room temperature and i put the RB flask to the freezer.
I let it in 24 hours but i don't have any crystals which appears and i don't know where i fail in the procedure ? Could someone help me ? 
Thanks all.
[Edited on 6-5-2012 by newbies]
[Edited on 6-5-2012 by newbies]
|
|
|
solo
International Hazard
Posts: 3967
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline
Mood: ....getting old and drowning in a sea of knowledge
|
|
...you need to give the reference credit for your synthesis....i.e.
http://www.erowid.org/archive/rhodium/chemistry/phenyl-2-nit...
.......
Phenyl-2-nitropropene (n-Butylamine Catalysis)
Written by Zorohustra
Chemicals
80 mL Toluene (ACS)
40 mL Benzaldehyde (~99%)
30 mL Nitroethane (>99%)
10 mL n-Butylamine (p.a.)
Procedure
The reactants and amine catalysts were dissolved in the toluene in a 250mL RB flask, boiling stones were added and a Dean-Stark setup was rigged (10mL
trap). The goal was to boil the solution quite heavily to achieve fast dripping from the double surface condenser, a heating mantle was used.
When the solution had boiled for an hour 2.7mL water was in the trap. At six hours something like 7.0mL (100% of theory) had settled in the trap,
perhaps this happened some thirty minutes earlier, because the chemist took a short nap. The solution was dumped into a 250mL beaker, and allowed to
cool to room temperature, it was seeded with some phenylnitropropene crystals, and slowly cooled to around -10°C (freezer). The crystals looked
really nice and no further purification was needed (Yield 35g). The filtrate was concentrated under vacuum and cooled like above. Dirty crystals fell
and they were recrystallized from 50mL MeOH (Yield 6g). The total yield from both crops amounted to 41g (64%)
Hmm, hmm the chemist thought, perhaps Benzene will increase the yield, its lower boiling point would probably decrease destruction of formed
phenylnitropropene. Said and done, the same procedure, setup and chemicals as above was used in a second experiment, but with 80mL of nice 99.9%
benzene as solvent instead of the toluene.
After boiling the solution for 6h, 3.3mL of water was collected, after 14h 6.7mL, and after 19h 6.9mL was collected, and the chemist turned the
heating off, thinking: "I will never get 7.0mL due to the higher solubility of water in Benzene then in Toluene, I'm just killing yield now"
The solution was concentrated under vacuum, care taken never even to smell any Benzene. Dumped the solution in a 250mL beaker, it solidified
completely and just 150mL of MeOH was added. This was enough to dissolve the crystals when boiling. Yield: 42g (65.6%).
All right, the yield is just above 60% with both Toluene and Benzene, lower temperature results in a slower reaction. But there are cases when
n-Butylamine is a much faster catalyst and the temperature is even lower, such as when using MeOH as solvent. The chemist decided to try the reaction
and setup once more but with 60mL cyclohexane as solvent, but after 20h of boiling only 4.2mL water had collected in the trap, and when cooling down
the clear yellow reaction mixture crystals refused to form, so the solution is concentrated under vacuum to give crystals, but the yield sucked as
less than 10g of product could be isolated (<15% yield).
..........
...then read well and follow instructions....things like crystal seeding, concentration of solution, removal of toluene, and other details you seem
to overlooked....solo
[Edited on 6-5-2012 by solo]
It's better to die on your feet, than live on your knees....Emiliano Zapata.
|
|
|
newbies
Harmless
Posts: 11
Registered: 21-1-2012
Member Is Offline
Mood: No Mood
|
|
I know this road but i don't have phenylnitropropene crystals to do seeding how can i do without ? I also scratched the walls of my RB flask but
nothing...
|
|
|
kristofvagyok
National Hazard
Posts: 659
Registered: 6-4-2012
Location: Europe
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by newbies  | | I know this road but i don't have phenylnitropropene crystals to do seeding how can i do without ? I also scratched the walls of my RB flask but
nothing... |
I know an old prof who said once: "drugs are for people who have no idea in chemistry".
If the crystallization doesn't starts, then distill off some of the solvent, cool it down in an ice-salt or ice-cc.acid bath and it will crystalline
out. If still not, than scratch the walls or just wait and live it in the fridge for a couple of hours...
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
|
|
newbies
Harmless
Posts: 11
Registered: 21-1-2012
Member Is Offline
Mood: No Mood
|
|
Many thanks but i don't make phenylnitropropene for drugs.
I only want to do that because it seemed to easy for me because i just start in organic chemistry.
|
|
|
Nicodem
Super Moderator
Posts: 4230
Registered: 28-12-2004
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by newbies | Many thanks but i don't make phenylnitropropene for drugs.
I only want to do that because it seemed to easy for me because i just start in organic chemistry. |
Insulting our intelligence is not going to convince anyone that spoon-feeding you is of any use. Organic chemistry is a science and you have no
respect for science, as you showed already in the first post where you failed to give the reference. Furthermore, you did not invest any effort
whatsoever in reading upon the crystallization techniques or searching the forum before opening a new thread. This same topic was already discussed
just a couple of weeks ago. I'm locking this thread, because it is nothing but one more drug cook spoon-feeding attempt with no scientific value.
|
|
|
Nicodem
|
Thread Closed
6-5-2012 at 05:56 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
