« The intricacies of solving for an unknown structure using solution NMR data | Main | Why collect NMR or MS^n data? »

February 15, 2008

Comments

Feed You can follow this conversation by subscribing to the comment feed for this post.

ChemSpiderMan

It may be safe to make an assumption in a comparison of methylbenzene and ethylbenzene. And, in theory, if you are always comparing similar molecules you may be lucky with this approach. However, when you take into account the complexities of relaxation times on quaternary carbons it is very easy to get confused in terms of the quantitative approach you are suggesting. Been there done that...been confused. 2D NMR is the way out of the problem.

Gary Martin

Mixtures of alkyl benzenes are fine. Not only are there considerations of relaxation times for quats as Chemspiderman notes, there is also the aspect of preferred axes of roation that can have a significant impact on protonated carbon relaxation times. IMHO, after 30+ years of doing 13C NMR, this is an approach that must be used with very considerable caution when dealing with unknowns even if they're simple alkyl benzene analogs. When it comes to anything more complex, don't go there...

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name is required. Email address will not be displayed with the comment.)