A broad stretching band around 3000 cm–1 and two narrower stretching bands around 1725 cm–1 and 1240 cm–1...?

A broad stretching band around 3000 cm–1 and two narrower stretching bands around 1725 cm–1 and 1240 cm–1. It also has a bending vibration around 932 cm–1....

A) butylamine

B) propanoic acid

C) 1-butanol

D) 2-chlorobutane

I HAVE NO IDEA. I think it is the propanoic acid but I could be wrong. We don't even have any scaling graphs to look off of, and all the example IR graphs very in so many ways that I can't make a clear distinction. PLEASE HELP!

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  • 7 years ago
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    I really don't care about 932 cm-1. Few people look at any detail at that part of the spectrum.

    You are told a broad band around 3000 cm-1. That is going to be an -OH group, or could be a wet sample. Anyway, it could be an acid or an alcohol.

    But now, focus on 1725 cm-1. That is the carbonyl region. That is a region you want to become very familiar with, as it is one of the first places you look for clues to the compound. Ester, aldehyde, ketone, carboxylic acid, amide, etc.

    But since you are probably starting out, you want to get clues on everything. So 932 cm-1 is the OH out of plane bending of an acid dimer. And 1240 cm-1 is the C-O coupled with the OH in plane bending. And 1725 cm-1 is the C=O

    It also means the IR spectrum was measured in a solvent. As the use of a solvent intensifies those bands that are listed.

    Oh, the IR is textbook B.

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