Dehydration of amides to give nitriles
Description: Primary amides can be converted to nitriles with a dehydrating reagent such as P2O5 .
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Real-Life Examples:
Org. Synth. 1930, 10, 66
DOI Link: 10.15227/orgsyn.010.0066
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Org. Synth. 1945, 25, 61
DOI Link: 10.15227/orgsyn.025.0061
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Org. Synth. 1945, 25, 63
DOI Link: 10.15227/orgsyn.025.0063
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Org. Synth. 1950, 30, 22
DOI Link: 10.15227/orgsyn.030.0022
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Org. Synth. 1950, 30, 46
DOI Link: 10.15227/orgsyn.030.0046
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Org. Synth. 1953, 33, 52
DOI Link: 10.15227/orgsyn.033.0052
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How will be convert the 4 hydroxy benzoic acid to 4 hydroxy benzacynide.
I take it you mean benzonitrile ?
One way to do it would be to convert the carboxylic acid to an acid chloride (SOCl2) followed by formation of an amide with NH3 . That gives a primary amide which could then be converted into the nitrile with a dehydrating reagent.
how to convert the 2-amino melonamide to 2-amino melononitrile, can we use P2O5? or is there any specific reagent for the above particular reaction?
You would definitely want to protect the amine first.
What is the role of oxygen in the reagent?
Phosphate ions are great leaving groups. Oxygen stabilizes the negative charge.
In step 3, why lone pair on nitrogen attack the carbon ( arrow F) ?
You can look at this mechanism as “elimination”, or, “1,2-elimination”. It’s kicking off a good leaving group (the phosphate) and forming a new C-N pi bond in the process.
Hi James,
My question may sound silly,but i seriously have no idea.Why ‘P’ in P2O5 is attracted by the pi bonds and not the lone pairs of Amine group?
Lone pair of amide is strongly donating into carbonyl carbon – there is pseudo double bond character between carbon and nitrogen. Oxygen is very nucleophilic.