Lightning quick chemical reactions measured using chromofores – University of Copenhagen

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06 October 2011

Lightning quick chemical reactions measured using chromofores

When new chemical substances are created in the test tube, the processes are much too small to see, and too fast to keep up with. Indeed, chemists have traditionally employed the educated guess when determining how a new molecule was created.
A new Danish study demonstrates that one can keep up with these lightning fast reactions by measuring the part of the molecule which gives off colour, the so called chromofores.

Kemiker Rasmus Brogaard has refined a method to scrutinize lightning fast chemical reactions

The study, undertaken by the chemist Rasmus Brogaard of the University of Copenhagen will be published in the prestigious journal, "Journal of Physical Chemistry A"

We can see most colours because a molecule's chromofore absorbs a specific wavelength of visible light and reflects another. Rasmus Brogaard is nearing the completion of his PhD studies in the Femtosecond-laboratory at the University of Copenhagen's Department of Chemistry. Here, he has shot chromofores with extremely short-lived pulses of laser light, in part to begin the chemical reaction and also to "photograph" the reaction.

Laser as starter button and film camera

By using laser pulses in this manner, he has used an unusually simple method to demonstrate that one can influence and research ultra-fast chemical changes by illuminating chromofores. It is a knowledge that can prove important to all chemists who are trying to develop more efficient chemical processes and avoid byproducts. Nowhere might this be more true than in medicinal chemistry, where even trace amounts of impurities can lead to the most serious of side effects in an otherwise excellent drug.

The shortest second

The laser pulses are so short-lasting that a pulse in relation to a second is like a second in relation to the age of the universe. Femtosecond pulses, as they are called, make it possible to investigate the position of atoms within molecules with such a short interval between that one is able to map the entire process, nearly to the most minute detail..