Photochromism in view

Sunglasses

Source: Fotolia

A context-based chemistry practical highlighting the importance of chemical kinetics and spectroscopy in commercial photochromic dyes

The practical described here demonstrates the commercial exploitation of synthetic organic chemistry in a specific application, ie photochromism. This depends on the ability of chemists to control the physicochemical properties - ie half-lives, rate constants, activation energies, uv-visible absorption properties - of the chemical reactions involved.  

The practical highlights the importance of chemical kinetics (specifically first-order kinetics) and spectrophotometry within an industrial context and how an understanding of these topics aids interpretation of technical product data. We use this practical in the first-year chemistry course at Keele University, but it could be adapted to suit students at other levels. 

Undergraduate experiments based on the kinetics and spectroscopy of photochromism are not new.1 However, I reasoned that such practical work would be enhanced if students were to work with actual commercial dyes. With this in mind I contacted James Robinson, an international company that manufactures speciality chemicals, who supplied samples of photochromic dyes in addition to providing me with valuable feedback on the proposed practical. 

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