Infrared Spectroscopy

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Presumed knowledge

In order to get the full benefit from this resource you should:

- have a rough idea of what organic chemistry is and the role it plays in society.

- know how to draw the molecules and reactions of organic chemistry. This includes using the zig-zag skeletal form of representing organic chemistry structures and a good grasp of the chemical element symbols.


Spectroscopy is a group of analytical techniques used by organic chemists in order to determine what structure an organic molecule has. In each form of spectroscopy, a molecule interacts with a form of electromagnetic radiation to give a readout allowing information to be gleaned regarding the molecule’s structure.

There are several types that are used on a regular basis:

Nuclear magnetic resonance (NMR) spectroscopy: proton and carbon forms, allows the hydrocarbon backbone of an organic structure to be determined. Also provides additional information regarding molecule symmetry.

X-ray crystallography: electrons scatter X-rays which allows the three-dimensional structure of a molecule to be determined. Sensitive enough to allow assignment of stereochemistry, bond lengths and angles.

Infrared spectroscopy: allows the functional groups in a molecule to be determined.

Mass spectrometry: allows the mass of the molecule and correspondingly, the molecular formula of the molecule to be determined.

In this resource, we will cover infrared spectroscopy.