[wonj]

Here's the link to the IR:  http://www.chemicalbook.com/SpectrumEN_126-81-8_IR1.htm

I would expected the cyclic ketone to be somewhere around 1715, possibly even 1690 if there is an enol form providing conjugation.  But the 1613 peak seems like an alkene peak to me.  In which case, if there is an enol present, why is there no broad OH peak? 

Thanks for the help

[discodermolide]

Here's the link to the IR:  http://www.chemicalbook.com/SpectrumEN_126-81-8_IR1.htm

I would expected the cyclic ketone to be somewhere around 1715, possibly even 1690 if there is an enol form providing conjugation.  But the 1613 peak seems like an alkene peak to me.  In which case, if there is an enol present, why is there no broad OH peak? 

Thanks for the help

According to the Wiki page the following applies:
"Dimedone is in equilibrium with its tautomer in solution — in a 2:1 keto to enol ratio in chloroform"

Now I didn't see what the IR was run in: neat, in solution, KBr. Any of these could have an affect on the keto-enol equilibrium.
This may be why you don't see an enol signal.

[wonj]

I wouldn't be too surprised if no enol showed up, but I'm still confused as to why there seems to be only an alkene peak and no carbonyl peak at all.  Whether or not one of the ketones tautomerized, there would have to be a carbonyl peak in both cases, right? 

(I also don't know much where this IR came from, it was just handed out to us as a reference.)

[discodermolide]

I wouldn't be too surprised if no enol showed up, but I'm still confused as to why there seems to be only an alkene peak and no carbonyl peak at all.  Whether or not one of the ketones tautomerized, there would have to be a carbonyl peak in both cases, right? 

(I also don't know much where this IR came from, it was just handed out to us as a reference.)

You should see a carbonyl peak, and you do have tautomers.
Look on the web for a better IR.

[orgopete]

I would expected the cyclic ketone to be somewhere around 1715, possibly even 1690 if there is an enol form providing conjugation.  But the 1613 peak seems like an alkene peak to me.  In which case, if there is an enol present, why is there no broad OH peak? 

I think sometimes you have to interpret the spectra differently. Let us simply assume this is dimedone and the largest peak is at 1613 cm-1 and the OH is very broad and shifted to lower frequencies. If you look at the IR of a carboxylic acid, you will see the OH is quite different than an alcohol. Carboxylic acids are notably hydrogen bonded dimers. Although a diketone could chelate the enol proton, but in dimedone that isn't possible. I should assume it is a dimer similar to a carboxylic acid.

Since the IR shows a significant amount of enol present, I don't know whether the C=O peak has shifted to still lower frequencies due to electron donation from the oxygen or if the intensity has greatly decreased and the 1613 cm-1 peak is a C=C peak. You might search for acetylacetone in the SDBS database and you should see similar features.