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-   -   NMR question about chemical shifts and frequency difference between two lines? (http://www.bionmr.com/forum/nmr-questions-answers-24/nmr-question-about-chemical-shifts-frequency-difference-between-two-lines-5806/)

rumberg 05-20-2005 02:37 AM

NMR question about chemical shifts and frequency difference between two lines?
 
The 13C chemical shifts for the carbonyl and methyl resonances of acetone are 206.68 and29.92 ppm, respectively (referenced to TMS at 0 ppm).a) If this spectrum was run on a Varian INOVA 400 NMR spectrometer, what is the frequencydifference in Hz between the two lines? (Assume <ref = 100.0650368 MHz) (2 points)b) What is the difference in magnetic field experienced by the carbonyl carbon vs. the methylcarbons. (4 points)thank you Allision!!so then i haver a difference of 17,717 Hz.for b) now I do not have any textbooks for this course but i did go to the library and picked up 4 differnet books on the subject. can someone tell me if this is rightb) Bo = 2(3.14rad)(20711x10^6 s^-1) / 67.2640x10^6 T^-1S^-1= 1.93TandBo = 2(3.14rad)(2994x10^6 s^-1) / 67.2640x10^6 T^-1S^-1=2.80Tdifference = 0.87 Tis this correct?

Allison aka Nice Lady 05-20-2005 02:37 AM

NMR question about chemical shifts and frequency difference between two lines?
 
If a chemical shift is 206.98 ppm, that's 206.98 ppm x 100.0650378. So the actual shift from 400 MHz is 20,711.5 Hz. The shift for 29.92 ppm can be calculated the same way. Find the difference.The answer to part B should be explained in your textbook. If you don't have a good one find one in the library.I don't mean internet. I mean library.<br />
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