[rleung]

Hi,

I am confused as to why this molecule only gives 3 signals in a 13C NMR.  Is it because the signal for the C that has a double bond to O is so small that it become insignificant?  Even if it becomes insignificant, technically, it produces a signal, right?  Thanks.

Ryan

[Borek]

Which molecule?

[sdekivit]

Hi,

I am confused as to why this molecule only gives 3 signals in a 13C NMR.  Is it because the signal for the C that has a double bond to O is so small that it become insignificant?  Even if it becomes insignificant, technically, it produces a signal, right?  Thanks.

Ryan

if it's a ketone the C-peak of this group will be less intens (1/3 of the C-peak where H is bound to C)

[rleung]

Sorry about leaving it out the first time...

[Yggdrasil]

What kind of spectrum are you talking about?  The carbonyl carbon should show up on a regular C-NMR spectrum, but it would not show up on a DEPT spectrum, because there are no hydrogens attatched to it.

[Albert]

As you see, generally speaking, this is the spectrum you would get.

[Albert]

...and here is the DEPT-spectrum you probably have seen. (I agree with Yggdrasil)

[rleung]

Thanks so much.  I think the book may have been referring to a DEPT spectrum.  

Ryan