16.0: Prelude to Radical Reactions The subject of this chapter is single-electron chemistry, and the free radical intermediates that are involved in single electron reaction steps. 16.1: Overview of Single-Electron Reactions and Free Radicals Beginning with acid-base reactions in chapter x and continuing though the chapters on nucleophilic substitution, carbonyl addition, acyl substitution, a-carbon chemistry, and electrophilic reactions , we have been studying reaction mechanisms in which both electrons in a covalent bond or lone pair move in the same direction. In this chapter, we learn about reactions in which the key steps involve the movement of single electrons. 16.2: Radical Chain Reactions Because of their high reactivity, free radicals have the potential to be extremely powerful chemical tools - but as we will see in this chapter, they can also be extremely harmful in a biological/environmental context. Key to understanding many types of radical reactions is the idea of a radical chain reaction 16.3: Useful Polymers formed by Radical Chain Reactions Many familiar household materials polymers made from radical chain reaction processes. Polyethylene (PET), the plastic material used to make soft drink bottles and many other kinds of packaging, is produced by the radical polymerization of ethylene (ethylene is a common name for what we call 'ethene' in IUPAC nomenclature). The process begins when a radical initiator such as benzoyl peroxide undergoes homolytic cleavage at high temperature. 16.4: Destruction of the Ozone Layer by a Radical Chain Reaction The high reactivity of free radicals and the multiplicative nature of radical chain reactions can be useful in the synthesis of materials such as polyethylene plastic - but these same factors can also result in dangerous consequences in a biological or ecological context. 16.5: Oxidative Damage to cells, Vitamin C, and Scurvy While the hydroxide radical can be a beneficial 'detergent' in the atmosphere, it is harmful when present in a living cell. Hydroxide radical is one of the reactive oxygen species (ROS) that we learned about earlier. 16.6: Flavin as a One-Electron Carrier In chapter 15 we saw how a nicotinamide and flavin coenzymes can act as acceptors or donors of two electrons in hydride-transfer redox steps. Recall that it was mentioned that flavin, (but not nicotinamide) can also participate in single-electron transfer steps through a stabilized radical intermediate called a semiquinone. 16.E: Radical Reactions (Exercises)