Question

A 1H NMR signal is observed at 227.0 Hz (downfield of TMS) on a 1.40 × 102-MHz instrument.

a) What is the observed chemical shift in parts per million (ppm)?

b) What is the chemical shift, in parts per million (ppm), if the sample is analyzed with a 400.0-MHz instrument?

c) Where will the proton signal appear, in hertz, if the sample is analyzed with a 400.0-MHz instrument?

Answer 1

A 1H NMR signal is observed at 227.0 Hz (downfield of TMS) on a 1.40 × 102-MHz instrument.

a) What is the observed chemical shift in parts per million (ppm)?

Solution :- chemical shift in ppm = 227.0 Hz /140 MHz = 1.62 ppm

b) What is the chemical shift, in parts per million (ppm), if the sample is analyzed with a 400.0-MHz instrument?

Solution :- the chemical shift value is proportional to the applied field so the when the 400.0 MHz instrument is used then chemical shift value also increase

So the ppm remains the same that is 1.62 ppm

c) Where will the proton signal appear, in hertz, if the sample is analyzed with a 400.0-MHz instrument?

Solution :- chemical shift in ppm = (400.0 MHz / 140 MHz)*(227.0 Hz) = 648 Hz downfield.