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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: metallica00789 on April 07, 2013, 05:56:16 PM

Title: Ester and Kenton C13 NMR
Post by: metallica00789 on April 07, 2013, 05:56:16 PM

Hi,
Why the carbon of esters groups has a lower C13 NMR chemical shift (170-185ppm) compared to the carbon of ketone groups (205-220 ppm). I am thinking that since the carbon of esters are next two electronegative atoms (oxygen), it should more deshielded, and thus having a higher chemical shift.
Thank you

Title: Re: Ester and Kenton C13 NMR
Post by: salteen on April 07, 2013, 06:23:50 PM

You are correct in that a more electron-deficient atom will have a higher chemical shift. Try drawing the resonance structures for a ketone vs an ester, and compare the amount of electron density each carbonyl carbon experiences.