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The hydrolysis of amides



hey above is the mechanism that I have deduced from my textbook that I have drawn out on chemsketch for the hydrolysis of an amide using an acid catalyst on the first one (HCL) and an alkali catalyst on the second (NaOH). I was just confirming whether this is indeed the mechanism because the textbook isn't great. the textbook seems to suggest that the catalyst is introduced after the initial hydrolysis. Hence the second arrow is where the catalyst affects the constitutent molecules of the hydrolysed amide.

The acid one (the first one) makes sense to me - but the second one not so much...is it saying that the OH- recieved the hydrogen from the carboxylic acid and the nitrogen positive ion is then attracted to the negatively charged oxygen atom?

many thanks
(edited 12 years ago)
Original post by Cyanohydrin


hey above is the mechanism that I have deduced from my textbook that I have drawn out on chemsketch for the hydrolysis of an amide using an acid catalyst on the first one (HCL) and an alkali catalyst on the second (NaOH). I was just confirming whether this is indeed the mechanism because the textbook isn't great. the textbook seems to suggest that the catalyst is introduced after the initial hydrolysis. Hence the second arrow is where the catalyst affects the constitutent molecules of the hydrolysed amide.

The acid one (the first one) makes sense to me - but the second one not so much...is it saying that the OH- recieved the hydrogen from the carboxylic acid and the nitrogen positive ion is then attracted to the negatively charged oxygen atom?

many thanks


Hey there mate,

your gonna have to bare with me typing ... but i think that the reaction mechanism is slightly more complicated in reality.... but i think what you have done should be fine for A2?


Anyways, if you are interested in the true mechanism... the acid catalysed reaction can be explained in the 6 steps below:

Step 1: Protonation of the Oxygen from C=O by accepting a H+... this leaves the O with a +ve charge overall

Step 2: Water in the solution acts a nucleophile... and attacks the slightly positive carbon atom attached to the +ve oxygen... and this happens, the C=O bond breaks to form a C-O bond... there is also another C-O bond from the water....we now have a tetrahedral intermediate... note, the oxygen on the water has a +ve charge..

Step 3: Deprotonation of the oxygen from the water... this is to neutralise the charge... the deprotonation happens by another water molecule

Step 4: Time to kick out the amine... but it needs to become a better leaving group first.... protonation of the nitrogen takes place... acid/base reaction like step 1... this leaves the nitrogen with a +ve charge..

Step 5: The Original C=O bond forms as electrons from the oxygen kick back to the carbon which then kicks out the NH3+ group... it becomes a NH3 with a neutral charge since it gained some electrons... the oxygen that donated the electrons is now positive

Step 6: The H on the +ve oxygen is now deprotonated by the NH3 group to form a neutral oxygen atom on the now carboxlyic acid and NH4+

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