Louis Pasteur

Louis Pasteur (December 27 1822 – September 28 1895) was a French microbiologist and chemist. He is known to the general public for his demonstration of the germ theory of disease and his development techniques of inoculation, most notably the first vaccine against rabies; however, he also made a major discovery in the field of chemistry, regarding asymmetric molecules and the polarization of light.

Work on chirality and the polarization of light

In his early works as a chemist he resolved a problem concerning the nature of tartaric acid (1849). A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by chemical synthesis had no such effect, even though its reactions were identical and its elemental composition was the same.

Related Topics:
Tartaric acid - 1849 - Polarization - Chemical synthesis

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Pasteur noticed, upon examination of the tiny crystals of tartaric acid, that the crystals came in two asymmetric forms that were mirror images of one another. Tediously sorting the crystals by hand gave two forms of tartaric acid: solutions of one form rotated polarised light clockwise, while the other form rotated light counterclockwise. An equal mix of the two had no effect on polarized light. Pasteur correctly deduced that the tartaric acid molecule was asymmetric and could exist in two different forms that resemble one another as a left- and right-hand glove resemble one another. As the first demonstration of chiral molecules, it was quite an achievement, but Pasteur then went on to his more famous work in the field of biology/medicine.

Related Topics:
Crystal - Chiral

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His doctoral thesis on crystallographygot him a position of professor of chemistry at the Faculté (College) of Strasbourg.

Related Topics:
Crystallography - Strasbourg

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In 1854, he was named Dean of the new College of Science in Lille.

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In 1857, he was made administrator and director of scientific studies of the École Normale Supérieure.

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