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Chapter

Cover Organic Chemistry

Reactions involving Radicals  

This chapter outlines the formation of radicals by homolysis. It emphasizes that the mechanisms of radical reactions are quite different from those of polar reactions: most occur by radical chain mechanisms. The chapter then examines the stability of radicals and the radical chain reactions. It then shifts to emphasize that radical reactions are important in biology and medicine. Radicals are in fact all around us: a normal oxygen molecule is a diradical, reactive oxygen species such as superoxide anion, hydroperoxyl radical, and hydroxyl radical are believed to be implicated in the ageing process. Finally, the chapter examines radical polymerization. Radical polymerization is an important industrial process for the production of useful plastics. It then studies the formation of radical ions by single electron transfer, and their reactions as well as the electrolytic reactions.

Chapter

Cover Organic Chemistry

Radical reactions  

This chapter highlights radical reactions. This is the most important way of making radicals: unpairing a pair of electrons by homolysis, making two new radicals. Temperatures of over 200°C will homolyse most bonds; on the other hand, some weak bonds will undergo homolysis at temperatures little above room temperature. Light is a possible energy source for the homolysis of bonds too. There are a number of compounds whose homolysis is particularly important to chemists. They all have weak σ bonds, and generate radicals that can be put to some chemical use. The chapter looks at electron spin resonance, radical–radical reactions, radical chain reactions, the chlorination of alkanes, and allylic bromination.

Chapter

Cover Radical Chemistry: The Fundamentals

The elementary reaction steps  

This chapter analyzes the reactions of compounds that yield products which may be isolated and purified and involve radicals, outlining individual reaction steps in which the radicals may participate. It focuses on the variety of elementary unit steps, such as radical addition and atom-transfer. It also discusses essential unit steps with interactions between two radicals, such as halt chain reactions by giving non-radical products. The chapter describes the interaction of two radicals that form non-radical products. The chapter cites two possible processes: radical coupling and disproportionation. It examines the interaction between ethyl and methyl, noting that the term dimerisation is strictly restricted to the coupling of two identical radicals.

Chapter

Cover Making the Transition to University Chemistry

Hydrocarbons: Alkanes  

This chapter tackles the concept of alkanes, a type of hydrocarbon. It defines a hydrocarbon as containing hydrogen and carbon only. Alkanes are saturated hydrocarbons. Crude oil is an example of a complex mixture of hydrocarbons, most of which are alkanes. Fractional distillation allows for the separation of the mixture and relies on the different fractions with varying boiling points. The chapter explores the mechanism for radical chain reaction and photochemical halogenation which occur through the reaction of an alkane with a halogen. Finally, the combustion of alkanes is considered to be the most significant reaction commercially since it is also a radical chain reaction.