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Topic: Ester and Kenton C13 NMR  (Read 2494 times)

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Offline metallica00789

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Ester and Kenton C13 NMR
« 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

Offline salteen

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Re: Ester and Kenton C13 NMR
« Reply #1 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.

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