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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: Senobim on September 09, 2015, 01:46:41 PM

Title: problem from the text book
Post by: Senobim on September 09, 2015, 01:46:41 PM

Hello guys, I've got lost with 11

Information i have: C₉H₈O Dbe = 6
From 13C: with DEPT 44ppm - CH2; 125 - CH (benzene ring?) ; 127 - CH (double bond?); 138 - C; 215 - C (probably carbonyl) IR suggests strong band at 1746 cm^-1
From 1H: singlet with 4H at ~7.2 ppm probably benzene ring with identical 1,4 substitution
             singlet with 4H at ~3.5 ppm i would say CH2

From now on I am totally lost, most confusing thing is singlet with 4H at 7.2 ppm, because i can't think any structure with identical substitution of benzene ring from carbonyl and double bond.

Title: Re: problem from the text book
Post by: Babcock_Hall on September 09, 2015, 03:12:00 PM

Have you considered the possibility of accidental chemical shift equivalence?

Title: Re: problem from the text book
Post by: Senobim on September 09, 2015, 03:38:10 PM

with that in mind, only thing i could think of is 2-indanone. 1,2-disubstituded benzene

Title: Re: problem from the text book
Post by: Senobim on September 10, 2015, 02:59:57 AM

i found .jpg :) is it 2-indanone after all?

Title: Re: problem from the text book
Post by: Babcock_Hall on September 10, 2015, 11:57:08 AM

I think it is reasonable, but I would check the structure against the data in several ways.  For instance, is the IR absorption at the correct position for a ketone that is not in conjugation with the aromatic ring?  Is a chemical shift of about 3.5 reasonable for benzylic hydrogen atoms that are also in an alpha position with respect to a ketone?  Is 215 ppm reasonable for a ketone versus other carbonyl functional groups?