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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: MahderA on February 20, 2017, 03:51:32 PM

Title: Finding the mystery ester strucuture using NMR
Post by: MahderA on February 20, 2017, 03:51:32 PM

Dear all,

I have an unknown ester with the chemical formula C9H10O2 that is used as a flavoring agent in candies. It exhibits the following H-NMR and C-NMR (Attached file: unknown ester NMR)

Based on the NMR peaks I believe the unknown is benzyl acetate , as the C-NMR and the first two peaks of H-NMR are identical to the unknown NMR (Attached file: benzyl acetate NMR).

Knowing that aromatic protons are not equivalent, as shown in the unknown's H-NMR at 7.4 and 7.5 ppm, I do not know why the aromatic protons for benzyl acetate are integrated and shown as a singlet.
Is this just due to the sensitivity of the prediction algorithm (I am using Chembiodraw)? Or benzyl acetate is not the unknown?

Your help is greatly appreciated!

Title: Re: Finding the mystery ester strucuture using NMR
Post by: AWK on February 20, 2017, 06:16:18 PM

It seems to me that your H-NMR shows very good resolution with comparison to literature spectrum ~100 MHz.

Title: Re: Finding the mystery ester strucuture using NMR
Post by: wildfyr on February 20, 2017, 10:10:31 PM

His lit NMRs are predictions from chemdraw. Look up the real lit NMRs on SDBS.

Title: Re: Finding the mystery ester strucuture using NMR
Post by: Dan on February 21, 2017, 01:54:04 AM

Quote from: MahderA on February 20, 2017, 03:51:32 PM

Is this just due to the sensitivity of the prediction algorithm (I am using Chembiodraw)? Or benzyl acetate is not the unknown?

ChemDraw predictions are not perfect, they don't match the real spectra 100%, that is normal.

Title: Re: Finding the mystery ester strucuture using NMR
Post by: Irlanur on February 21, 2017, 07:21:16 AM

Just pointing out that we are comparing two non-experimental spectra here...