I am looking forward for the most plausible mechanism of the reaction between acid amide (derivative of carboxylic acid) and HNO2.

although i know the general reaction ar written in my book ie.

 

 

R-CONH2 + HNO2 == (HEAT) == >R-COOH + N2(evolved)+H2O

 

mechanism would hel me identifying which kinds of acid amides and participate in such reactions.

 

R-CONH2 + HNO2 == (HEAT) == >R-COOH + N2(evolved)+H2O

 

 

Looking at the final products from the equation, I think the reaction mechanism may be somewhat similar to the reactions of primary amines with nitrous acid

 

So if that's the case, then the mechanism would be something like this:

 

Reagent: sodium nitrite, NaNO2 + HCl (aq)

 

Since the diazonium salts is not stable, it decomposes readily to form nitrogen gas and a carbocation.

 

The carbocation then reacts with water to give the carboxylic acid.

 

Overall equation:

 

I am not really certain, so do correct me if i am wrong.

thanks for your valuable effort the mechanism seems to be correct.

one thing i also wanted to know if u can clear my doubt,

 

 

while drawing the resonating structures of chlorobenzene how can we show partial double bond character on chlorine though it cannot expand its octet?

It can use one of its free electron pairs, which, in turn, puts a negative charge on the entire ring.