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Topic: which is correct  (Read 7670 times)

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NISHANT

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which is correct
« on: April 30, 2005, 09:26:52 AM »
which will be the product when acetaldehyde is treated with dilute alkali:
a}acetic acid
b}alpha-hydroxy butanal
Of course we know that this at first glance should be beta-hydroxy butanal by aldol condensation,but here the option contains {alpha type},so I want to know that is there a slight chance that acetic acid may also be produced along with the aldol product?

Offline Winga

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Re:which is correct
« Reply #1 on: April 30, 2005, 12:35:02 PM »
b

NISHANT

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Re:which is correct
« Reply #2 on: April 30, 2005, 12:38:28 PM »
but by aldol condensation beta hydroxy butanal should form?

GCT

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Re:which is correct
« Reply #3 on: April 30, 2005, 06:01:44 PM »
it can undergo a cannizzaro reaction with the acetic acid as one of the products.

NISHANT

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Re:which is correct
« Reply #4 on: May 01, 2005, 12:20:02 AM »
but isn't it necessary for cannizaro that there should be no alpha hydrogens.And isn't there a slight chance that it may be oxidised by the dilute alkali althogh the chance may be quite low

Offline Winga

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Re:which is correct
« Reply #5 on: May 01, 2005, 12:50:36 AM »
Sorry, I didn't read it carefully.

In this case, I think both of them are not the products.

Present of alpha-hydrogens, Cannizzaro reaction doesn't occur.

In aldol condensation, after beta-hydroxy butanal is formed, it will undergo dehydration, and conjugated enone forms.

NISHANT

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Re:which is correct
« Reply #6 on: May 01, 2005, 01:50:39 AM »
but isn't there a slight chance that the aldehyde could be oxidised to carboxylic acid by the dilute base.

NISHANT

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Re:which is correct
« Reply #7 on: May 01, 2005, 01:52:40 AM »
the reason I am stressing so much on it's oxidation to aetic acid is because of the fact it is very difficult for this question to be wrong as it came in an exam at national level.

NISHANT

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Re:which is correct
« Reply #8 on: May 01, 2005, 12:16:56 PM »
so isn't there a chance that the aldehyde could be oxidised to acetic acid by dilute alkali?

Offline movies

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Re:which is correct
« Reply #9 on: May 01, 2005, 01:29:26 PM »
Without an additional oxidizing agent, probably not.  The only way I can think of is through the Canizzaro reaction, which was already mentioned.  That reaction will definitely be slower than the aldol reaction (or condensation).

Garneck

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Re:which is correct
« Reply #10 on: May 05, 2005, 02:29:24 AM »
I can't imagine how you can oxidise an aldehyde to acetic acid in a alkali solution.

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