Sciencemadness Discussion Board

P2NP microwave crystallization problem

a-SalviaLover - 25-10-2006 at 07:08

SWIM recently did the P2NP synthesis using Ammonium Acetate as a catalyst and microwave heating. He used no solvent. Here is the refference:
Quote:

In a typical synthetic procedure, a mixture of benzaldehyde 5a (0.106 g, 1 retool) and nitromethane 6a (0.061 g, 1 mmol) is placed in a glass tube containing ammonium acetate (0.019 g, 0.25 retool) and is exposed 5133 to pulsed microwave irradiation 28 in an alumina bath for 2 min using an unmodified microwave oven operating at its 40% power. 25 The reaction mixture is cooled to room temperature (~ 1 min) and is irradiated again for 2 min. After two such successive irradiations (2 min) and cooling (~ 1 min) sequences, another 1 mmol of nitromethane is added to the reaction mixture that is further irradiated for two similar successions. After completion of the reaction (followed by TLC), the reaction mixture is passed through a short silica gel column using hexane:AcOEt (9:1,v/v) as an eluent. The evaporation of the solvent on a rotary evaporator affords I~-nitrostyrene (8a). Yields 83%


He used 15 ml benzaldehyde, 11 ml nitroethane and 3 gr Ammonium acetate. He heated it the same way as described above, but 6 times instead of 4. He put a baggie with ice on the top of the flask to condense the vapours and was changing periodically the ice when it melted. Only after the first heating did the solution begin to get yellow. After the sixth it was clear and dark yellow. After cooling the solution became opaque, but no crystals appeared to form. He tried everything described in the refs he had: he scratched the walls of the flask with a glass rod, he added some water, he even washed it thoroughly with water in order to remove the ammonium acetate. Nothing seemed to help. Filtration didn't get him anything.

SWIM would be be grateful if a more advanced chemist than him knows how to help him crystallize his stuff. Although he has read many refferences and books of practical chemistry and he has always had excelent grades in chemistry, SWIM has a very little practical experience. In fact, this is his first organic synthesis.

He also has another question. Since HgCl2 was inaccessible to him, SWIM bought HgI2. He then realised than it has a rather poor solubility. In what can you dissolve HgI2? If it is completely insoluble in anything, how can you convert it to another more soluble salt?

SWIM would like to thank you in advance for your support!

[Edited on 25-10-2006 by a-SalviaLover]

woelen - 25-10-2006 at 07:14

Quote:
SWIM recently did the P2NP synthesis using Ammonium Acetate [...]

Isn't this time of the year too cold for swimming? I usually only swim on hot summer afternoons....

Sergei_Eisenstein - 25-10-2006 at 09:48

You could try the following, though you may be doing something illegal: evaporate volatiles under reduced pressure. If the residue remains an oil, add a few times its volume of water and stir vehemently. Cooling with an icebath may help. If no nitrostyrene falls out, your product may contain too much benzaldehyde and remain an oil.

not_important - 25-10-2006 at 18:09

If there is an excess of aldehyde, the researcher might take up the reaction mix in a non-water soluble solvent and wash that with a cold, strong but not saturated, solution of sodium bisulfite (NaHSO3) to remove aldehyde as the bisulfite complex. Addition to the carbon-carbon double bond is possible, but the aldehyde should react more quickly.


Hmmm - boil the HgI2 with sodium carbonate, possibly changing the Na2CO3 solution once. Then dissolve the oxide/basic carbonate in the desired acid.



SWIM would not try this, as they would not hear of it. Self deluding cowards learn little - witness the current 'leaders' of the US.

Cloner - 1-11-2006 at 09:08

Another very insoluble iodine salt is silver iodide. This is so much more insoluble, that a full exchange takes place between silver salt and mercuric iodide, though I am not sure about silver chloride (which is very insoluble as well and might be impractical here). Would mercuric nitrate be useful?

[Edited on 1-11-2006 by Cloner]

[Edited on 1-11-2006 by Cloner]

Boomer - 2-11-2006 at 09:49

Speed as a first organic synth? - Try some nitro first. This way, in case of missing lab skillz, you won't poison your customers.

Dextrose - 4-11-2006 at 18:35

Use another primary amine (salt), Methylamine.HCl should give kick-ass yields (Osmium).

AFOAF did this:

120 mmole 9 gr. / 8.7 ml. Nitroethane 98% (75.06 m)

Dissolved in ~20 ml. IPA under stirring at RT.

Then the following was added

20 mmole 0.9 gr. / 1.1 ml. Ethylamine 70% (aq) (45,07 m)

* In practice 0.027 mole - 1.2 ml.

Started stirring (7/10) with reflux in waterbath in a saucepan (Stirrer 150*C)

* Fine piss-yellow color

T = 25*C
T+15 = 50*C
T+30 = 60*C
T+37 = 70*C

* Stopped heating

T+45 = 65*C
T+60 = 55*C
T+75 = 50*C

Watherbath removed, and the following was added

30 mmole 1.8 gr. / 1.73 ml. GAA (60,05 m)

* In theory 32.5 mmole - 1.82 ml.

T+85 = 40*C, put in fridge.
T+135 = put in freezer.

Yield:

80-85% (? mmole - forgot to calculate) 2,5-Dimethoxy-Phenyl-2-Nitropropene (209,20 m)

a-SalviaLover - 28-11-2006 at 07:39

Quote:
Originally posted by a-SalviaLover
SWIM recently did the P2NP synthesis using Ammonium Acetate as a catalyst and microwave heating. He used no solvent. Here is the refference:


He used 15 ml benzaldehyde, 11 ml nitroethane and 3 gr Ammonium acetate. He heated it the same way as described above, but 6 times instead of 4. He put a baggie with ice on the top of the flask to condense the vapours and was changing periodically the ice when it melted. Only after the first heating did the solution begin to get yellow. After the sixth it was clear and dark yellow. After cooling the solution became opaque, but no crystals appeared to form. He tried everything described in the refs he had: he scratched the walls of the flask with a glass rod, he added some water, he even washed it thoroughly with water in order to remove the ammonium acetate. Nothing seemed to help. Filtration didn't get him anything.

SWIM would be be grateful if a more advanced chemist than him knows how to help him crystallize his stuff. Although he has read many refferences and books of practical chemistry and he has always had excelent grades in chemistry, SWIM has a very little practical experience. In fact, this is his first organic synthesis.

He also has another question. Since HgCl2 was inaccessible to him, SWIM bought HgI2. He then realised than it has a rather poor solubility. In what can you dissolve HgI2? If it is completely insoluble in anything, how can you convert it to another more soluble salt?

SWIM would like to thank you in advance for your support!

[Edited on 25-10-2006 by a-SalviaLover]


I decided that the solution might not be basic enough, because ammonium acetate is not as basic as methylamine, so I decided to dissolve small amount NaOH in water and add it to the nitro. Loads of cyrstals appeared both in the water and the nitro, but they are white in colour, so I'd like to ask whether the NaOH has reacted with something or this is the nitro?

As for the HgI2 there is completely no need to disolve the salt. The reaction startswithin 10 mins after you put some of the salt in the mixture with the Al.

[Edited on 28-11-2006 by a-SalviaLover]

chochu3 - 28-11-2006 at 19:01

Its your nitroethane forming a salt with the sodium hydroxide if you search around you will find that someone was trying to purify their nitromethane by creating a salt from the nitro and the hydroxide. Same principal applies to what you have done.

jon - 28-11-2006 at 22:41

ohh HgI2 is more soluble in solutions of potasium or sodium iodides. this is because it forms a complex with it.

Boomer - 29-11-2006 at 00:45

*Loads* of crystals from *a small amount* of NaOH? Unless he added a lot, a little formed nitroethane/sodium salt should be soluble. At least I did not have crystals from the start when trying to purify nitromethane fuel via this method.

Could it be the reaction did not proceed as planned with the acetate, but after adding NaOH in the cold he got a Henry reaction started? Would the nitro-alcohol crystallize spontaneously?

a-SalviaLover - 30-11-2006 at 12:19

The crystals werent that much actually. If nitroethane forms a salt with NaOH why wouldn't p2np do so?
Yields are unacceptable without crystallization. What would you advise me to do with this product? Methl/butylamine are unavailable. So is any of the purifying techniques described in the papers of this synth (column chromatigraphy, fractional distillation etc.).
I also have another question.

How can you neutralize the smell of p2np/benz/nitro? It stinks up the whole house and my microwave.

Polverone - 30-11-2006 at 16:34

We've had some complaints lately about the number of production-oriented drug threads that appear here. There's a lot of interesting chemistry involved in the production of drugs, pharmaceutically-employed and otherwise, but this really isn't an appropriate forum for people to ask for help in following established "recipes." We've long had this policy for energetic materials, and now it needs to be clear that it applies to drugs as well.

If you (a collective you, not just the first poster in this thread) can write about a step of a drug procedure in language that would be appropriate to (say) Organic Syntheses, then even fairly mundane and practical questions may be asked here. But if you can't do that, production-oriented discussions of drugs and immediate drug precursors are unwelcome here. The standards for writing about novel or theoretical chemistry are somewhat lower. You need to wear your best Professor Science hat when discussing mundane aspects of production. Otherwise your threads will be closed like this one.

[Edited on 12-1-2006 by Polverone]