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Old Oct 15th 2016, 02:51 PM   #1
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Join Date: Oct 2016
Location: Minneapolis, MN
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jeherohaku is on a distinguished road
NMR interpretation

Hi everyone,
I'm new to the forum and registered today because I just can't figure out this NMR spectrum from my advanced organic lab (and please correct me if this is in the wrong area, I'm in my senior year as an undergrad at the U of M).

We performed a Diels-Alder reaction between anthracene-9-methanol and N-methylmaleimide in water. The product structure is (hopefully) embedded in a picture along with the NMR I submitted of the crude product. The NMR was done at 300 MHz in CDCl3.

I have tried comparing mine to a spectrum I found in the literature (Pinto et al. Green Chem., 2013,15, 970-975, DOI:10.1039/C3GC36881E) and I have most of the same peaks but am lacking their peak at 2.94.

I'm really confused about the aromatic region because I have the multiplet at around 7.25 and then two doublets downfield of that, but the doublets each integrated to 1H and the multiplet integrated to 7H's but I only see 8 total H's in the structure that should be in that region (all the ones still attached to the aromatic rings). The tall singlet at 2.54 I believe to be from the N-CH3, but I'm also at a loss for which specific protons lead to the remaining doublets and multiplet. I also originally integrated the two doublets at 5.14 and 4.98 as one doublet of doublets but the J value I got was around 48Hz and my professor said that was basically impossible.

Basically, I've been looking at this thing for a long time but I'm at wits end. Can anyone help shed some light on this?

Also, my TLC monitoring the reaction showed some trace of starting material (which I have the NMR for as well but I don't see any similar peaks except in the aromatic region) and two spots that I assumed to be some byproduct along with the desired product. I'm not really sure if what I'm seeing in my NMR is possibly some byproduct that's confusing me. I'll also include the reaction scheme if that helps anyone.

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diels alder, nmr

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