Infrared Spectra
Home Table of Contents Preliminary Information Amines Amides Amino Acids Ring Compounds Infrared Spectra Lab Identification Wrap-Up

 

Infrared Spectra

We have just two infrared spectra in this lesson. Both have N-H absorptions that show up to the left of the 3000 cm-1 mark. Look in your workbook for more readable copies of these spectra on which you can also take notes.

Amine

This (Spectrum #13 in your workbook) is the IR spectrum of dibutylamine. It has an N-H absorption to the left of 3000 cm-1 and a mass of C-H absorptions to the right of 3000 cm-1 and nothing else until you get to the fingerprint region down past 1500 cm-1.

Infrared spectrum of dibutylamine. [65irsp13.JPG]

 

Amide

This (Spectrum #14 in your workbook) is the IR spectrum of acetamide. It is not a particularly good spectrum. In part that is because the compound is a solid rather than a liquid. However, there are some things we can pick out. First of all there are two N-H absorptions to the left of 3000 cm-1 and a C-H absorption, to the right of 3000 cm-1. Also, down in the double bond region there is a large absorption between 1600 cm-1 and 1700 cm-1 that corresponds to the C=O bond.

Infrared spectrum of acetamide. [65irsp14.JPG]

 

These are the things that characterize the amine and amide spectra:

the N-H absorptions to the left of 3000 cm-1 for both amines and amides, and
the C=O absorptions down in the double bond region for the amides.

 

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