Question

The chemical shift for chloroform's proton is 7 ppm above TMS. If the protons in TMS absorb at 300 MHz, what frequency (in MHz) does chloroform's proton absorb?

Answer 1

Formula:

(or ppm) = (frequency:sample - frequency:reference)/(operating frequency of spectrometer)

Reference is usually 0 so frequency:reference = operating frequency of spectrometer = 300 MHz in our case.

Consider frequency:sample = x, frequency:reference = 30010⁶ Hz and operating frequency of spectrometer = 300 10⁶ Hz.

= (x - 300 10⁶ ) / (300 10⁶) = 7

(x - 300 10⁶ ) = 210010⁶

x = 210010⁶ + 300 10⁶

x = 2400 10⁶ Hz = 2400 MHz.

Thus Chloroform's proton absorbs at 2400 MHz.