Provide Structure of C10H13NO2 Given IR and NMR Data?

NetherCraft 0

Provide a structure for the following compound:

C10H13NO2;

IR: 3285, 1659, 1246 cm–1;

1H NMR spectrum, along with my best guess, which was incorrect: i58.tinypic.com/i1h0zr.png

Here are the hints I have been provided:

The resonance at δ 7.6 is a broad singlet.

The IR absorptions indicate the presence of two functional groups, one of which is a carboxylic acid derivative. The coupled quartet and triplet splittings indicate the presence of which common alkyl group? Remember the n+1 rule: n adjacent protons cause the resonance of an observed proton to be split into n+1 lines. The aromatic splitting patterns indicate a para substitution pattern.

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The IR data indicate the presence of a secondary amide (has an N–H bond).

Here is what it said about my attempt: The chemical shifts don’t match the proposed structure. For example, nothing in your structure accounts for the magnitude of the chemical shift of the quartet; N-adjacent alkyl group protons resonate below δ 3, and a phenolic OH resonance typically appears at δ 5–6.

I answered the way I did because I thought the coupled quartet and triplet splittings indicated an ethyl substituent, and my book says a phenolic OH resonance is δ 6-8, so I was surprised to see the disagreement. I didn’t know about the N-H bond when I answered. I thought that the 3285 IR frequency might be the OH group, the 1659 frequency a CC double bond and/or CO double bond, and the 1246 frequency an sp3 CO single bond.

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Any help is appreciated!

ANSWER:

A para-substituted benzene ring (two branches on opposite sides):

One branch is -NHC(=O)CH3

The other branch is -OCH2CH3

1 Answer

  • ANSWER:

    A para-substituted benzene ring (two branches on opposite sides):

    One branch is -NHC(=O)CH3

    The other branch is -OCH2CH3


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