OBLONG
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Seperating 2-phenylpropionaldehyde from phenyl-2-propanone
Hello people of Sciencemadness, I was wondering how I would separate a mixture of 2-phenylpropionaldehyde and phenyl-2-propanone at an unknown ratio,
meaning a bisulfite adduct probably cannot be used since it will react with the ketone as well. I read here that
| Quote: |
A good idea for separating a mixture of the two is to oxidize the mixture with a mild oxidant which won't affect the P2P, but which will oxidize the
aldehyde to 2-phenylpropionic acid.
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What oxidizer should I use, or are there any other methods for separation? Also, I am aware that phenyl-2-propanone is a commonly used precursor to
methamphetamine, and I have no intention to synthesize any illegal substances, and since drug-related discussion isn't allowed on Sciencemadness, I
apologise if I this post is breaking any rules, and the moderator is welcome to delete it. Thank you
[Edited on 25-9-2016 by OBLONG]
[Edited on 25-9-2016 by OBLONG]
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Texium
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Thread Moved
25-9-2016 at 06:18 |
Metacelsus
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I'd expect them to be separable using column chromatography.
Also, if you're looking for mild oxidants, Fehling's (or Tollens') reagent will selectively oxidize the aldehyde.
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OBLONG
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Thanks you Metacelsus. I haven't heard of either Fehling's or Tollen's reagent, I'll try it out when I can.
[Edited on 25-9-2016 by OBLONG]
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Darkstar
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Quote: Originally posted by OBLONG  | | Also, I am aware that phenyl-2-propanone is a commonly used precursor to methamphetamine, and I have no intention to synthesize any illegal
substances, and since drug-related discussion isn't allowed on Sciencemadness, I apologise if I this post is breaking any rules, and the moderator is
welcome to delete it. |
If you're in the US, please be aware that simply possessing phenylacetone can get you into some serious trouble if you were ever caught. Unlike most
meth precursors, which are just DEA List I or II, phenylacetone is a straight-up Schedule II controlled substance, making its mere possession without
a DEA license illegal, regardless of intentions.
*Edit* - And just for future reference, drug-related discussion is allowed here as long as it's genuine and scientific in nature. It's
low-effort spoon-feeding requests that are frowned upon here. Legitimate questions regarding the actual chemistry involved in the synthesis of illegal
drugs, even when the end goal is ultimately to implement that chemistry, are perfectly acceptable as long as they are are asked in a scientific manner
using proper chemical nomenclature. It helps to demonstrate that you have at least attempted to do some form of research on your own beforehand,
though.
[Edited on 9-25-2016 by Darkstar]
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OBLONG
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Thanks Darkstar, I'm in Australia.
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solo
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There is a patent which talks about separating the adducts of aldehyde and ketones at a temp of somewhere in the 40˚C for one and above that for
the other.....if i can remember where i have i will post it.....solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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OBLONG
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That isn't going to work since the boiling points are just 6 degrees apart.
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Protium-1
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OBLONG, solo actually mentioned that some as-yet-unspecified "adduct" of said compound had a 40°C bp difference, inherently your point about the 6°C
bp difference of the base compounds you have in question is taken.
Also, judging by your disclaimer about appropriate discussions on this forum, I assume it is appropriate that you drop the 2-prefix from the aldehyde
name, unless that is truly what you intend.
Besides the Tollen's reagent, you could use Potassium Permanganate or Potassium Dichromate (both of which are commonly available) to selectively
oxidize the aldehyde to a carboxylic acid, leaving the ketone unreacted.
This is probably your best bet as it remains super easy to remove the carboxylic acid from the mixture with a mild Sodium Hydroxide solution, while
the ketone remains dissolved in most organic solvents.
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CuReUS
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you could also use the pinnick oxidation to convert your aldehyde to acid without affecting the ketone
there is another way but its not that practical 
if you can get some dimedone , you can form an adduct with phenylpropionaldehyde only
| Quote: | Dimedone (5,5-dimethylcyclohexane-1,3-dione) reacts to form a crystalline derivative ONLY with aldehydes.
The condensation products of dimedone and aldehyde are called alkylidene dimethones. The alkylidene dimethones are almost insoluble in water, but can
be crystallised from dilute ethanol.
Test Procedure.
Add 0.1 grams of the test-aldehyde to 5 mls of a 50/50% ethanol/water solution, add 2 mls of a 10% or saturated ethanolic solution of Dimedone.
If a precipitate does not form immediately, warm for 5 minutes; if the solution is still clear at the end of this period, add hot water until the
mixture is just cloudy and cool to about 5 oC. Collect the crystalline precipitate by filtration. |
https://the-hive.archive.erowid.org/forum/showflat.pl?Cat=&a...
[Edited on 26-9-2016 by CuReUS]
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OBLONG
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Sorry solo, I misunderstood. Protium-1, 2-phenylpropionaldehyde is the specific isomer I have. Also, thanks for pointing out that permanganate/dichromate doesn't oxodize the ketone. I'll
try to oxidize the aldehyde with permanganate and sodium hydroxide, which from my understanding should form the salt that can then be vacuum filtered
out, leaving just the ketone and any excess sodium hydroxide, potassium permanganate, and water.
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