Lecture 3 – The handed molecule

From the 1992 lecture brochure:

In this lecture we venture below the surface of objects at the human scale to reach the molecular level. We explore the assembly of molecules from atoms and show how minute they are on the scale of familiar objects.

Of the roughly ten million known molecules, with their immense diversity of possible molecular structures, we shall concentrate on molecules that contain the OH - hydroxyl - group, such as water, alcohol, anti-freeze and sugar. Spectroscopy will show us the OH group and other groups in these tiny collections of atoms and we shall see that this class of molecule is notorious for sticking together. We will look at the effects of such association on the behaviour and the properties of molecules.

Spectroscopy - the interaction of light with molecules - is a vital aspect of chemistry and we shall concentrate on a special interaction, that of plane polarised light with molecules of various kinds.

We take up the theme of molecular handedness by way of the observation of the rotation of plane polarised light by materials. We re-enact the deduction of molecular asymmetry by Pasteur in 1847, when he solved the mystery of the multiple tartaric acids. We look at the separation of right and left handed molecules - resolution - and we look at how handed molecules associate in special ways, particularly when they contain an OH group. We shall illustrate this association with very recent work on reactions at surfaces and in Lecture 5 see how such association produces the spiral (helical) molecules upon which life depends.


Natural world


BBC / Royal Institution




Charles Stirling



All lectures in the series