Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Telamond on February 06, 2009, 04:35:32 PM

Title: How do you explain a NMR spectrum in a lab report?
Post by: Telamond on February 06, 2009, 04:35:32 PM
I have a C- and a H-NMR spectrum. I know what all the peaks refers (all except for the aromatic carbons) to and which peaks goes to what carbon and adjacent hydrogen.

The only problem is that I have no idea on how to refer to the peaks. Is it okay to just write "Peak 3.794 and 3.7511 on the H-NMR spectrum is a doublet which refers to..."
Since I'm not certain of which peaks refers to what carbon in the aromatic, is it okay for me to say that peak 7.560 7.4510, 7.2945, 7.1883 are aromatic, or should I guess (I've never been a huge fan of writing guesses in reports).

Thanks in advance!
Title: Re: How do you explain a NMR spectrum in a lab report?
Post by: macman104 on February 06, 2009, 06:03:56 PM
Typically you report peaks and their multiplicity (doublet, singlet, etc.) and then the number of hydrogens that they integrate to.

In my lab reports I usually put the information in a table (maybe this will be for the H NMR of ethyl acetate (http://www.muhlenberg.edu/depts/chemistry/chem201woh/1Hethylacetate.html)), something like:

Position (ppm)Multiplicity# of Hydrogens
1.25Triplet3
2.0Singlet3
4.1Quartet2
Title: Re: How do you explain a NMR spectrum in a lab report?
Post by: alguno on February 07, 2009, 06:52:10 AM
Typically
(CDCl3,ppm): 1,25 (t,J= xHz, 3H), 2.0 (s,3H), 4.1 (q, J=xHz, 2H)
Title: Re: How do you explain a NMR spectrum in a lab report?
Post by: Dolphinsiu on February 15, 2009, 03:05:44 AM
Yes. Table form is very good for proton nmr. However, How about 13C NMR? since I am not the 13C NMR expert, how can I do in a table form? Also, multiplicity is always a singlet form. How about DEPT 45/DEPT 90/DEPT 135? How to do so?

Also, why is coupling constant all stated in proton nmr? Why is it important? It seems there is not relationship between the structure and coupling constant except oleic system, right?