Go with the most obvious one first...Carboxylic Acids will have a.pdf
- 1. Go with the most obvious one first... Carboxylic Acids: will have a really broad and large absorption range in the 3500-2500cm-1 area (aka. the "valley of the acid") as well as a carbonyl peak in the 1700cm-1 area. That would be spectrum 4. Alcohols:will also have a strong and broad absorption in the 3500-3000cm-1 region, but nowhere near as broad as the acid. It just looks like a really fat absorption line, rather than a well... Anyway, the characteristic spectrum for the alcohol is spectrum 5. Amines:lucky for you, the amine given in this question is a primary amine. There's going to be two N-H stretching peaks in the 3300cm-1 region. There's also no carbonyl on the structure given, so there should be no C=O stretching at 1700cm-1.This is spectrum 3. Don't worry about the small absorption in the 1500-1700cm-1 area. Now for the fine details... The ester and aldehyde spectra are pretty similar, but aldehydes absorb at around 2750cm-1. It's not totally clear on the spectra in the question but it looks like there's a 2750cm-1 absorption in spectrum 2, so I'd say that spectrum 2 is the aldehyde, and spectrum 1 is the ester. Summary: Spectrum 1 = structure B Spectrum 2 = structure E Spectrum 3 = structure C Spectrum 4 = structure D Spectrum 5 = structure A Solution Go with the most obvious one first... Carboxylic Acids: will have a really broad and large absorption range in the 3500-2500cm-1 area (aka. the "valley of the acid") as well as a carbonyl peak in the 1700cm-1 area. That would be spectrum 4. Alcohols:will also have a strong and broad absorption in the 3500-3000cm-1 region, but nowhere near as broad as the acid. It just looks like a really fat absorption line, rather than a well... Anyway, the characteristic spectrum for the alcohol is spectrum 5. Amines:lucky for you, the amine given in this question is a primary amine. There's going to be two N-H stretching peaks in the 3300cm-1 region. There's also no carbonyl on the structure given, so there should be no C=O stretching at 1700cm-1.This is spectrum 3. Don't worry about the small absorption in the 1500-1700cm-1 area.
- 2. Now for the fine details... The ester and aldehyde spectra are pretty similar, but aldehydes absorb at around 2750cm-1. It's not totally clear on the spectra in the question but it looks like there's a 2750cm-1 absorption in spectrum 2, so I'd say that spectrum 2 is the aldehyde, and spectrum 1 is the ester. Summary: Spectrum 1 = structure B Spectrum 2 = structure E Spectrum 3 = structure C Spectrum 4 = structure D Spectrum 5 = structure A