Distinguishing between IR specs: carboxylic acid vs. N-sub'd amide

[FROGGBUSTER]

Here is an IR spec of an N-substituted amide:

Would a carboxylic acid have a shorter and broader peak? Is that how you would distinguish between the 2?

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[mh0000]

carboxylic acid will have a broad peak around 3000 cm-1. The amide will have two peaks around 3300cm-1.

 

[toothhornet88]

Here is an IR spec of an N-substituted amide:

Would a carboxylic acid have a shorter and broader peak? Is that how you would distinguish between the 2?

Yes the carboxylic acid is way broader (3300-2500)

 

[PooyaH]

Both carboxylic acids and amides have a peak at 1720 for one thing. Then carboxylic acid has a broader peak than amides. Sometimes if the nitrogen of the amide is attached to 2 hydrogens, it would show 2 peaks around 3500.

 

[mh0000]

oh you said a substitude amide, then it will have one peak near 3300cm-1 or so

 

[wired202808]

I would say you could look at this if you have answer choice. N-H gives a peak at 3300 for NH and 2 speaks for NH2. But in terms of carboxylic acid you cant tell that you can only look for the OH and figure out if its an acid or alcohol n then look for a carbonyl at 1650. Although im sure this is easier to narrow on an exam with choices presented.