Study 6.34 Organic synthesis photobromination of progesterone

Case Study 6.34 Organic synthesis - photobromination of progesterone 

Although organic photochemistry has experienced remarkable growth, applications of photochemical synthetic methods in the chemical industry have been mostly limited to radical reactions, such as photohalogenation (this section), photopolymerization (Section 6.8.1) and to some extent photosulfochlorination, photooxidation (Section 6.7) and photonitrosylation, although some other reactions are also being used.155 

Cholesterol can be converted to vitamin D photochemically from 7-dehydrocholes-terol (provitamin D) (Special Topic 6.4) and this procedure is still used in industry.616 Vitamin D can also be made by irradiating yeasts rich in ergosterol. In addition, vitamin A (retinol) (see Special Topic 6.1) is synthesized by E Z photoisomerization (Section 6.1.1), sensitized by chlorophyll or other chromophores (Section 6.8) of its 11 -cis isomer, which is produced industrially by conventional synthetic steps.1310 

Photopolymerization, that is, a polymerization process initiated by photochemical production of the reactive species initiators (Section 6.8.1), is largely used in industry. Polymers can be synthesized by photoinitiation, but can also be modified by photochemical cross-linking (photochemical hardening or UV curing photoimaging photolithography see Special Topic 6.27). 

The most important and widespread applications of photochemistry are, of course, photoimaging techniques, such as photography and xerography (Special Topic 6.32).1313 Some other large-scale applications, such as environmental remediation of anthropogenic pollutants by photocatalytic processes (Special Topic 6.28) and potential applications such as photoelectrochemical cells (Special Topic 6.31) and artificial photosynthesis (Special Topic 6.26), are also discussed in the following text. 

---