(15 pts) Given the gyromagnetic ratio values for the following types of nuclei (

Question

(15 pts) Given the gyromagnetic ratio values for the following types of nuclei (in unit of 10 rad T s): 'H, 26.7522: 1BC, 6.7283; 3P, 10.841. (1) (5 pts) What are the resonance frequencies for C and 'P on a 300 MHz NMR spectrometer? (2) (5 pts) If a 2.2 ppm 'H chemical shift corresponds to a frequency difference of 1100 Hz from the reference point (i.e. 0 ppm) on a particular NMR spectrometer. What are the resonance frequencies for 'H and C on this spectrometer? (3) (5 pts) If the water H peak shows up at 4.7 ppm on a 400 MHz spectrometer, what will be the chemical shift value (in ppm) for the water 'H peak on a 600 MHz spectrometer?

Explanation / Answer

1. Resonance frequency r = ( / 2) * B0

Larmor frequency L (MHz )= (MHz/T) * B0(T) =300

For, 13C,   = 6.7283 x 107 rad T-1S-1 =10.7 MHZT-1,

Then B0 = 28 T

So, r = 47.68 MHz

Similarly, for 31P = 10.841 x 107 rad T-1S-1 =17.2 MHZT-1,

Then B0 = 17.44 T

So, r = 47.74 MHz

2. Chemical shift =(e - r) / 0 (MHz)

So for H, 2.2 = 1100/0 (MHz)

Then  0 = 500 MHz

So, r for H is 1100Hz

So, r for for 13C =(10.7/2)*(500/10.7)=79.5 Hz

3. Chemical shift (in ppm) will be constant for a particular proton for all the spectrometer. Hence,chemical shift value of the water peak is 4.7 ppm on a 600 MHz spctrometer.

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