kyanite
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Oxidation of Alcohols with Halides?
Does anybody know if this works? It seems dangerous, but also interesting because you don't hear about it so often.
Okay, so we know that Iodine is a mild oxidizer, but how about the others? It seems like it's possible, because you can do a haloform reaction on
ethanol with bleach (I don't remember where I read it from, probably here), making chloroform and sodium formate.
This is what I've found so far from my textbook:
CH3CH2OH + I2 ---> CH3CHO
then the ethanal goes on to react further.
You think chlorine can do the same?
What about secondary alcohols?
What do you guys think?
[Edited on 29-1-2005 by kyanite]
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Mumbles
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It can most definatly happen. The most common example is chloral hydrate. This is trichloracetaldehyde hydrate. It comes from Ethanol and Chlorine
gas with a CaO catalyst I believe.
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Synopsis
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All halides will oxidize most primary and secondary alcohols. Fluorine is the harshest oxidant, followed by chlorine, bromine and finally iodine as
the mildest.
It is rarely relied upon for preparative purposes because many side reactions may (and will) occur during the process. For example, the chlorination
of acetaldehyde usually proceeds quicker than the oxidation of ethanol. Thus, if you try to oxidize ethanol with chlorine, you most probably will get
chlorinated acetaldehyde, small amounts of acetaldehyde and unreated ethanol. If you use an excess of chlorine, you will be left with chloral.
I remeber reading a procedure once where they kept the alcohol at elevated temperature so that the aldehyde produced evaporated before being
chlorinated.
Now if the aldehyde you wish to produce dosen't bear alpha-hydrogens (like benzaldehyde, tert-butanal etc...) the oxidation might proceed
cleanly. However, if water is present in the reaction mixture, the aldehyde will quicky be oxidized to the carboxylic acid.
Theses complications also occurs with secondary alcohols, except for the overoxidation to the carboxylic acid.
Bleach and a catalytic amount of TEMPO (2,2,6,6-tetramethylpiperidine oxide, free radical) in dichloromethane oxidizes primary alcohols to aldehydes
and secondary alcohols to ketones in high yields. There are dozens of articles for this kind of oxidation in the recent litterature.
Hope it helps
Your theory is crazy, but it\'s not crazy enough to be true. - Niels Bohr
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phanchem
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Yes, with ethanol, chlorine works very well, but the actual product is chloral hydrate, or the old Mickey Finn. Trichloroacetaldehyde as the dihydroxy
acetal, not the aldehyde, because of the presence of the chlorines. Old chemistry, but good stuff.
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kyanite
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Too bad for the side reactions, or else this could have been a cheap alternative. Oh well, the bleach and catalysts look good anyhow.
Thanks for all you guys' help
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byko3y
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Oxidation of alcohols/aldehydes/ketones with chloride/bromine/iodine derrivatives is one easy yet extreemely complicated reaction. With ethanol
depending on conditions/oxidant it can give such major products as acetaldehyde, acetic acid, chloroacetaldehyde, chloral, ethyl acetate. Acidic and
strongly basic halides usually quickly halogenate the alcohol/aldehyde, while neutral bromine and iodine can selectively oxidize it to aldehyde.
It can even form ethyl hypochlorite.
[Edited on 22-9-2015 by byko3y]
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Hawkguy
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I did this a few weeks ago. The Chlorine I use successfully converted the Ethanol to Acetaldehyde, with a few drops of HCl as a catalyst. It takes a
shitload of Chlorine though.
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DraconicAcid
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Quote: Originally posted by Synopsis  | | All halides will oxidize most primary and secondary alcohols. Fluorine is the harshest oxidant, followed by chlorine, bromine and finally iodine as
the mildest. |
Halogens, not halides.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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