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Topic: Benzaldehyde + NH4CN then aqueous acidic workup  (Read 6080 times)

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Offline dan17

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Benzaldehyde + NH4CN then aqueous acidic workup
« on: December 14, 2010, 05:17:19 PM »
Hi, new to forums but my final in OCHEM2 is tomorrow and I'm looking at past exam keys and wanted to know if this was an error.

My current thinking is that NH4CN will lead to a nucleophilic addition of -CN at the carbonyl carbon. Then acidic workup hydrolyzes the CN into an amide. However that's not the product shown.
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Offline MissPhosgene

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #1 on: December 14, 2010, 05:38:42 PM »
It does seem like something is wrong.

You would get the a-hydroxy acid, not a-amino acid.

Could there be steps that aren't written in? Maybe the product is drawn incorrectly.
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Offline dan17

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #2 on: December 14, 2010, 05:53:05 PM »
Oh! actually, I didn't realize I was looking at an amino acid. Thanks, I found out that this is actually the "Strecker synthesis" of amino acids.
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Offline MissPhosgene

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #3 on: December 14, 2010, 06:20:10 PM »
Sweet. I did not know about this. It's a pretty cool reaction.
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Offline AWK

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #4 on: December 15, 2010, 04:01:04 AM »
NH4CN is very unstable (it is not a commercial reagent). Instead of it KCN or NaCN and ammonia are used)
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Offline MissPhosgene

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #5 on: December 15, 2010, 08:51:06 AM »
That was what I thought, so I assumed it would be a less-complicated reaction and go to the a-hydroxy acid. Wrong.
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Offline Hybrid

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Re: Benzaldehyde + NH4CN then aqueous acidic workup
« Reply #6 on: December 15, 2010, 12:09:30 PM »
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