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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: prophecy on May 29, 2008, 12:41:34 PM

Title: Spectroscopy exam question
Post by: prophecy on May 29, 2008, 12:41:34 PM

What is the correct structure for the following H1 NMR spectrum and IR spectrum. The incorrect structure on the following pdf document says isopropyl benzoate

Is it 4-isopropylbenzoic acid? The compounds molecular formula is C₁₀H₁₂O₂
It says an index of 7 on the top of the page and it really should be a 5.

Can someone who's knowledgeable about spectroscopy tell me the main elements that are wrong with the following page?

Thanks.

Title: Re: Spectroscopy exam question
Post by: Dan on May 30, 2008, 04:06:31 AM

4-Isopropylbenzoic acid is what I would say too.

The 6H, d and 1H, sept screams isopropyl group. 1705 in the IR is typical for a carboxylic acid.
You have 4 aromatic protons, and in order to get the two doublets you would need para substitution in the ring.

The problem with isopropyl benzoate is a) 1705 is really too low to be an ester and b) inconsistent with the aromatic region of the nmr

Title: Re: Spectroscopy exam question
Post by: Rico on May 30, 2008, 06:09:18 AM

Hey prophecy

The compound is definitely p-isopropylbenzoic acid (see ¹H-NMR og IR of p-isopropylbenzoic acid in jpeg files attached). A problem with the NMR on the page is that they do not show the acid proton above 12 ppm and the DBE is of course only 5 as you've pointed out yourself!

Rico

Title: Re: Spectroscopy exam question
Post by: prophecy on May 30, 2008, 02:29:46 PM

Thanks guys, I appreciate the help. Did you guys look at my other post by any chance?
Just simple oxidation of sulfides to sulfoxides and sulfones. I am just trying to confirm if it is correct.

Will.