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Topic: Questions about IR spectrum of acetonitrile  (Read 1099 times)

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Offline OrganicH2O

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Questions about IR spectrum of acetonitrile
« on: September 21, 2020, 04:45:09 PM »
I found this IR spectrum for acetonitrile on the Japanese Spectral Database:

I am wondering why acetonitrile has two stretching vibrations at about 2200. I don't think the CN triple bond would have a symmetric and asymetric stretch.

Also, it has stretching vibrations above 3000, including a sharp one at about 3200. It also has something that looks like a carbonyl overtone around 3500, but there is no corresponding strong stretch at about 1700. What's the deal there?
I have a Master's in organic chemistry and I am exposed to a LOT of different introductory organic chem classes in the course of my work, ranging from very basic to Harvard. I am here to refine my knowledge and consult with other organic chemistry nerds.

Offline mjc123

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Re: Questions about IR spectrum of acetonitrile
« Reply #1 on: September 22, 2020, 04:54:42 AM »
That link just takes me to the database, not the spectrum.

The two peaks at ca. 2200 are due to a Fermi resonance, I think with the combination 1376 + 918. 3164 could perhaps be the combination 2253 + 918. 3500 sounds like water - the sample is not dry.

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