chemist1243
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Oxime?!
So i finally got around to doing the good-old twodogs helional oxime synth that everyone likes to mention whenever the word “helional” comes out
of someone’s mouth.
I started out by dissolving 5.2g of hydroxylamine HCl in 10ml of water. 10g of helional dissolved in 20ml of isopropanol was added to the
hydroxylamine solution. I made a solution of 4g of sodium bicarbonate in 10ml of water and added it slowly to the hydroxylamine/helional solution with
magnetic stirring so that it didn’t foam up too much.
At this point, the solution was a hazy honey-dew green color. With stirring over a period of 12 hours the solution slowly progressed from yellow, to
darker yellow, and so on until the solution was almost brown.
I stopped the magnetic stirring and a goopy tan-brown liquid settled out to the bottom. I isolated the bottom layer using a sep funnel and then washed
it with water to remove most of the isopropanol. The tan liquid doesnt really have any smell except of some isopropanol that wasn’t washed out.
The twodogs synth said that if the aldehyde didn’t solidify then you are supposed to add more hydroxylamine and sodium carbonate, but instead i
stuck it in the freezer for 2 hours.
This did nothing except temporarily make it more viscous.
I’m worried that if i add more base or hydroxylamine all that will really happen is that whatever does solidify will be terribly impure with sodium
carbonate, sodium chloride, and other crap.
Is this liquid the oxime? At first i mistook it for the egg-yolk yellow goop that i get when i didnt keep the temp high enough the first time i did a
hydrogen peroxide oxidation via the one-pot amide synthesis from aldehydes, but what i got from the twodogs synth isn’t the same color and its not
as sticky either.
I’m not really concerned about getting the oxime in a solid form, but I wish there was a way to test out if this is my product. Any ideas? Thanks
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karlos³
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Mood: oxazolidinic 8)
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Its the oxime.
The density is as far as I know higher than water.
If you treat it right it will crystallise, that is under strong stirring with a bit of ethanol.
You can titrate hydroxylamine solutions by the way well, just add base slowly under stirring until its neutral, and use directly NaOH.
If you're worried about getting it to solidify, keep in mind then you can recrystallise it.
Thats is probably a good idea in every case, much better than using this oily blob directly 
| Quote: | | At first i mistook it for the egg-yolk yellow goop that i get when i didnt keep the temp high enough the first time i did a hydrogen peroxide
oxidation via the one-pot amide synthesis from aldehydes |
You mean the nitrile?
I have to say your oxime is really pretty strongly colored though and looks similar, how did that happen?
But I am still sure it is the oxime and not the nitrile, that would require conditions you did not have.
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chemist1243
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That is great to hear! i would like to share what happened when i sacrificed a small amount of the oxime to try solidifying by adding more carbonate
and hydroxylamine. I dissolved the oxime in isopropanol and then dissolved a pinch of hydroxylamine in water and added it to the isopropanol solution.
I turned up stirring and then slowly added about a teaspoon of sodium carbonate. I stirred it for and hour and then crashed it into ice water. A cloud
of “precipitate” that looked like thick vapor formed in the ice bath.
I am talking about the nitrile when i reference the egg yolk goop. It seems like whenever i do something with helional the nitrile forms. Anyways,
yeah, what i got from the two dogs synthesis is definitely not the nitrile. I dont really know why my oxime is so “strongly” colored, though. What
color is it supposed to be?
I’m gonna attempt a recrystalization, but i dont have any ethanol, so isopropanol will hopefully work just as well.
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chemist1243
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UPDATE: success
I’m not gonna try solidifying the oxime with recrystalization, because it did it itself! I heard somewhere that if you scrape the bottom of a beaker
containing solution that isn’t crystallizing easily, it can help the process speed up. So i did this for about a minute and left it. When i
comeback, there are a few crystals stuck at the bottom of the beaker. I scrape it some more, and then i leave it, and there are more crystals. So i
scrape it continuously and the color of the solution goes a few shades lighter and get way more thick, and its also more cloudy. Eventually, it
reaches the consistency of peanut butter, and then play dough, and then it crumbles into bits. I stir it around for good measure.
And just like that - everything is solid. I could theoretically use it as for whatever purpose one would use this product for.
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