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All 4 posts Subject: nitropropene reduction with sodium dithionite Please login to post Down

armageddon
(Hive Bee)
06-07-04 21:13
No 512055
      nitropropene reduction with sodium dithionite

Hi bees!

My buddy (whose name is replaced with SWIA for anonymity reasons wink ) was curious about the usability of sodium dithionite for reducing P2NP to phenylacetone oxime, like posted by Barium in Post 427794 (Barium: "Nitrostyrenes to oximes with sodium dithionite", Novel Discourse) - but when trying the described procedure he just ended up with some carbonate salt, so a different workup was used..

First he reduced the nitropropene as follows: in a 500ml RBF he placed 16.3g P2NP, wetted it down with 30ml EtOH and placed this on a water bath at 50°C. then, he added 50.6g Na2S2O4 (86% purity) and 100ml water and started stirring. After a few minutes, the temp. of the yellowish solution quickly rose to >70°C while the color disappreared almost completely. The heating bath was changed with a cooling bath (10°C) and the reaction was allowed to cool down to ~30°C.

Then SWIA added 100ml H2O, basified with conc. NaOH-solution to above pH10 and extracted three times with ethyl formate, washed the combined organic extracts with aequous NaOH, then 2x with brine, dried over Na2SO4 and removed the ethylformate by distillation under reduced pressure (200torr), leaving a pale cream-colored oil that slowly solidified on cooling (...it actually did so after 3 days).

Unfortunately he spilled a good amount of the ethylformate/oxime solution, so yields could not be taken - but the oxime is for sure free from carbonates and foul sulfurous smell! cool

SWIA told me he would try it again to be able to calculate yields... Of course I will post them as soon as I hear about it!

Note: SWIA told me one could also substitute the 30ml's alcohol with 20ml ethylacetate - it facilitates extracting the oxime afterwards, but the rxn time is lenghtened...

Greetz A

"..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."

armageddon
(Hive Bee)
06-07-04 22:47
No 512075
      possible hydrolysis

Another possiblility of purification is hydrolysing the oxime to the ketone. To accomplish this, SWIA just added the ethylformate solution (after washing it with brine) to 250ml 10% HCl and removed the ethylformate by distillation.

After removal of solvent hydrolysis was allowed for 2 hours at reflux, whereafter SWIA steam distilled the ketone under reduced pressure (200 torr), extracted the distillate w/DCM and removed it with an aspirator...

..another cheap route to P2Ps...

(EDIT) The so produced ketone still appeared to have a slight sulfur smell. Also it became yellowish/orange discolored although sitting in the freezer. SWIA concluded there was some alcohol and formic acid present, remaining from partial degradation of the ethylformate previously used to xtract the ketone (slowly decays into acid and alcohol upon contact with moisture). So he added a spatula tip of NaOH(s) to his ketone and vacuum distilled it over a 20cm vigreux - et voilà, nice refracting, greenish ketone that didn't change color anymore...(/EDIT)

greetz A

"..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."

Antibody2
(LinguisticBee)
06-09-04 00:20
No 512260
      why ethyl formate?

why ethyl formate?

We are all just witnesses.

armageddon
(Hive Bee)
06-09-04 00:56
No 512263
      no particular reason

Well, it was simply at hand in large quantity! And it pulls almost everything out of aequous solutions within two washes...
Furthermore it is easily removed from extracted products (bp 54°C at 760torr) - but apparently it is not very good for xtracting acid-sensitive/weakly basic compounds like oximes. crazy

(but many other bees use ethylacetate, and it has the same tendency to dissociate into acid and alcohol when coming in contact with water - and a higher bp...)

An example: Post 319296 (Rhodium: "P2P oxime in quantitative yield", Novel Discourse) (uses ethylacetate to extract P2P oxime from basic soln.)

BTW better don't add solid NaOH to your ketone, just use Na2CO3 (or other basic salt) - phenylacetone polymerises to something orange when treated with strong bases like NaOH (not easy to clean your glassware from this tar..)

Greetz A

"..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."

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	All 4 posts		Subject: nitropropene reduction with sodium dithionite		Please login to post		Down


		armageddon (Hive Bee) 06-07-04 21:13 No 512055				nitropropene reduction with sodium dithionite
						Hi bees! My buddy (whose name is replaced with SWIA for anonymity reasons ) was curious about the usability of sodium dithionite for reducing P2NP to phenylacetone oxime, like posted by Barium in Post 427794 (Barium: "Nitrostyrenes to oximes with sodium dithionite", Novel Discourse) - but when trying the described procedure he just ended up with some carbonate salt, so a different workup was used.. First he reduced the nitropropene as follows: in a 500ml RBF he placed 16.3g P2NP, wetted it down with 30ml EtOH and placed this on a water bath at 50°C. then, he added 50.6g Na2S2O4 (86% purity) and 100ml water and started stirring. After a few minutes, the temp. of the yellowish solution quickly rose to >70°C while the color disappreared almost completely. The heating bath was changed with a cooling bath (10°C) and the reaction was allowed to cool down to ~30°C. Then SWIA added 100ml H2O, basified with conc. NaOH-solution to above pH10 and extracted three times with ethyl formate, washed the combined organic extracts with aequous NaOH, then 2x with brine, dried over Na2SO4 and removed the ethylformate by distillation under reduced pressure (200torr), leaving a pale cream-colored oil that slowly solidified on cooling (...it actually did so after 3 days). Unfortunately he spilled a good amount of the ethylformate/oxime solution, so yields could not be taken - but the oxime is for sure free from carbonates and foul sulfurous smell! SWIA told me he would try it again to be able to calculate yields... Of course I will post them as soon as I hear about it! Note: SWIA told me one could also substitute the 30ml's alcohol with 20ml ethylacetate - it facilitates extracting the oxime afterwards, but the rxn time is lenghtened... Greetz A "..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."



		armageddon (Hive Bee) 06-07-04 22:47 No 512075				possible hydrolysis
						Another possiblility of purification is hydrolysing the oxime to the ketone. To accomplish this, SWIA just added the ethylformate solution (after washing it with brine) to 250ml 10% HCl and removed the ethylformate by distillation. After removal of solvent hydrolysis was allowed for 2 hours at reflux, whereafter SWIA steam distilled the ketone under reduced pressure (200 torr), extracted the distillate w/DCM and removed it with an aspirator... ..another cheap route to P2Ps... (EDIT) The so produced ketone still appeared to have a slight sulfur smell. Also it became yellowish/orange discolored although sitting in the freezer. SWIA concluded there was some alcohol and formic acid present, remaining from partial degradation of the ethylformate previously used to xtract the ketone (slowly decays into acid and alcohol upon contact with moisture). So he added a spatula tip of NaOH(s) to his ketone and vacuum distilled it over a 20cm vigreux - et voilà, nice refracting, greenish ketone that didn't change color anymore...(/EDIT) greetz A "..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."



		Antibody2 (LinguisticBee) 06-09-04 00:20 No 512260				why ethyl formate?
						why ethyl formate? We are all just witnesses.



		armageddon (Hive Bee) 06-09-04 00:56 No 512263				no particular reason
						Well, it was simply at hand in large quantity! And it pulls almost everything out of aequous solutions within two washes... Furthermore it is easily removed from extracted products (bp 54°C at 760torr) - but apparently it is not very good for xtracting acid-sensitive/weakly basic compounds like oximes. (but many other bees use ethylacetate, and it has the same tendency to dissociate into acid and alcohol when coming in contact with water - and a higher bp...) An example: Post 319296 (Rhodium: "P2P oxime in quantitative yield", Novel Discourse) (uses ethylacetate to extract P2P oxime from basic soln.) BTW better don't add solid NaOH to your ketone, just use Na2CO3 (or other basic salt) - phenylacetone polymerises to something orange when treated with strong bases like NaOH (not easy to clean your glassware from this tar..) Greetz A "..ein Trank von unterschiedlicher Farbe, in ihm ist Heilung für die Menschen."

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