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Topic: Synthesis of acetaldehyde  (Read 9161 times)

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Offline limpet chicken

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Synthesis of acetaldehyde
« on: November 28, 2004, 06:00:23 PM »
What options for the synthesis of aldehydes are available, I have been looking into it of late, and was curious about the synthesis of benzaldehyde of which there are a good few, and of acetaldehyde, for making acetic anhydride.

Are there any ways to add the -CHO group directly onto benzene to produce benzaldehyde? benzaldehyde is watched or controlled for some reason or other pertaining to clandestine synthesis I believe, although what I can't remember, but benzene is quite easily available, I am looking for possible routs from alkenes to the aldehydes, and indeed, aldehyde preperation in general. Preferably those that stand some chance of success in a "ghetto" setup, I.E those not requiring catalytic hydrogenation and such tedious things.
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Offline jdurg

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Re:Synthesis of acetaldehyde
« Reply #1 on: November 28, 2004, 10:46:01 PM »
Every Friday and Saturday night I tend to produce mass quantities of acetaldehyde from ethanol.  It happens right here in me liver.   ;D  Sadly, it gets metabolized immediately into acetic acid.  I'm guessing you could probably reflux concentrated ethanol with concentrated sulfuric acid which may remove a water molecule, thus giving you acetaldehyde.  (Though that's just a guess and I'm not sure if that would work).
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Re:Synthesis of acetaldehyde
« Reply #2 on: November 29, 2004, 01:37:49 PM »
Out of curiosity, how is acetaldehyde used to make acetic anhydride?  It's in the wrong oxidation state.

There are lots of ways to formylate aromatic systems.  Two of the favorites: Gatterman-Koch, Villsmaier-Haack.



Offline limpet chicken

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Re:Synthesis of acetaldehyde
« Reply #3 on: November 29, 2004, 02:40:24 PM »
Jdurg, refluxing concentrated H2SO4 will join two molecules of ethanol together by forming a bond between the ethanol and an oxygen molecule, giving diethyl ether.
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Offline jdurg

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Re:Synthesis of acetaldehyde
« Reply #4 on: November 29, 2004, 09:18:36 PM »
Jdurg, refluxing concentrated H2SO4 will join two molecules of ethanol together by forming a bond between the ethanol and an oxygen molecule, giving diethyl ether.

Hmm...  I wonder if glacial acetic acid could be dehydrated by concentrated sulfuric acid in a reflux, or if acetone could be "cracked" using sulfuric acid?
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