2.9 Skincare

Can result in molecules gaining sufficient energy for bonds to be broken - responsible for sunburn and contributes to aging of skin

Cause wrinkles by breaking down collagen, creating substances called free radicals that inhibit the natural repair of the skin

Chemical species that contains one unpaired electron and is highly reactive

Have unpaired electrons and are highly reactive

UV light provides energy for the homolytic fission of halogen into reactive halogen atoms or free radicals

Free radicals collide with other species but the number of free radicals is maintained

Free radical are used up by collision with eachother

Initiation, propagation, termination

• Reaction is initiated by UV and once started can continue in the dark • Other substitution products are made such as Ch2Br2, CHBr3, CBr4, together with longer alkanes

Present in many cosmetic products, they contain molecules which can react with free radicals to form stable molecules and prevent chain reaction (melatonin, vitamin E)