This video describes the basic concepts of nuclear magnetic resonance spectroscopy, NMR spectroscopy. It also elaborates the instrumentation of NMR spectroscopy. It explains the information that could be gathered from NMR spectrum with an example..
Learning Outcomes
You will be able to
state the principle of nuclear magnetic resonance (NMR) spectroscopy.
explain the instrumentation in detail and working of NMR spectroscopy.
discuss the NMR spectrum with an example.
list out the applications of NMR spectroscopy.
NMR Spectroscopy is a technique used to determine the structure, dynamics, reaction state and chemical environment of the molecules present in the sample placed in the external magnetic field based on absorption of radio waves (4900 MHz).
Nuclei of atoms have spin and they are electrically charged.
When placed in external magnetic field, the axis of the spin aligns parallel or antiparallel (opposite) to the axis of the external magnetic field.

Nuclei of some atoms have spin and they are electrically charged.
When nuclei are placed in an external magnetic field, the axis of the spin aligns parallel or antiparallel (opposite) to the axis of the external magnetic field.
When the nuclei are subjected to radio waves, the nuclei which are aligned parallel (lower energy level/stable state) to the axis of the external magnetic field absorbs energy to undergo spinflip and becomes antiparallel (higher energy level/unstable state) to the axis of the external magnetic field.
When the spinflip occurs, the nuclei are said to be in resonance with the external magnetic field.
Sample tube – The sample is introduced in a cylindrical tube (8.3 cm long and 0.3 cm diameter) and placed in an external magnetic field.
Magnetic coil – It generates magnetic field when current flows through it.
Permanent magnet – It provides uniform magnetic field.
Radio frequency transmitter – It provides powerful and short pulse radio waves.
Radio frequency receiver – It detects the NMR signals (radio waves when the spinflip occurs).
Recorder – The data is processed in the data processor and the recorder records the intensity of each signal with a specific chemical shift to give a NMR spectrum.

Chemical shift (d) – It represents the position of signal (resonance frequency) in the NMR spectrum of the observed nuclei relative to the reference/internal standard.
No. of signals – Different types of protons are present in a molecule.
Relative areas of the signal – No. of equivalent protons (same type) present.
Position of signal (chemical shift) – Type of proton present.
Splitting pattern – No. of neighbouring protons.