# 15: Oxidation and Reduction Reactions

• 15.1: Prelude to Oxidation and Reduction Reactions
This chapter is dedicated to redox chemistry. We'll begin with a reminder of what you learned in General Chemistry about the fundamentals of redox reactions in the context of inorganic elements such as iron, copper and zinc: reduction is a gain of electrons, and oxidation is a loss of electrons.
• 15.2: Oxidation and Reduction of Organic Compounds - An Overview
You are undoubtedly already familiar with the general idea of oxidation and reduction: you learned in general chemistry that when a compound or element is oxidized it loses electrons, and when it is reduced it gains electrons. You also know that oxidation and reduction reactions occur in tandem: if one species is oxidized, another must be reduced at the same time - thus the term 'redox reaction'.
• 15.3: Oxidation and Reduction in the Context of Metabolism
Think back again to the redox chemistry that you learned in your general chemistry course. A common experiment in a general chemistry lab is to set up a galvanic cell consisting of a copper electrode immersed in an aqueous copper nitrate solution, connected by a wire to a zinc electrode immersed in an aqueous zinc nitrate solution.
• 15.4: Hydrogenation of Carbonyl and Imine Groups
Many of the redox reactions that you will encounter when studying the central metabolic pathways are classified as hydrogenation or dehydrogenation reactions. Hydrogenation is simply the net addition of a hydrogen (H2) molecule to a compound, in the form of a hydride ion (H- , a proton plus a pair of electrons) and a proton.
• 15.5: Hydrogenation of alkenes and Dehydrogenation of Alkanes
We turn next to reactions in which a hydrogen molecule is added to the double bond of an alkene, forming an alkane - and the reverse, in which $$H_2$$ is eliminated from an alkane to form an alkene. Many biochemical reactions of this type involve unsaturated thioesters.
• 15.6: Monitoring Hydrogenation and Dehydrogenation Reactions by UV Spectroscopy
In order to study any enzyme-catalyzed reaction, a researcher must have available some sort of test, or assay, in order to observe and measure the reaction's progress and measure its rate. In many cases, an assay simply involves running the reaction for a specified length of time, then isolating and quantifying the product using a separation technique such as high performance liquid chromatography (HPLC) or gas chromatography (GC).
• 15.7: Redox Reactions of Thiols and Disulfides
The interconversion between dithiol and disulfide groups is a redox reaction: the free dithiol form is in the reduced state, and the disulfide form is in the oxidized state.
• 15.8: Flavin-Dependent Monooxygenase Reactions - Hydroxylation, Epoxidation, and the Baeyer-Villiger Oxidation
Below are two examples of biochemical transformations catalyzed by monooxygenase enzymes: one is a hydroxylation, the other is an epoxidation (an epoxide functional group is composed of a three-membered carbon-carbon-oxygen ring).
• 15.9: Hydrogen Peroxide is a Harmful - Reactive Oxygen Species
We get our energy from the oxidation of organic molecules such as fat and carbohydrates, as electrons from these reduced compounds are transferred to molecular oxygen, thereby reducing it to water. Reducing O2 , however, turns out to be a hazardous activity: harmful side products called reactive oxygen species (ROS) are inevitably formed in the process.
• 15.E: Oxidation and Reduction Reactions (Exercises)
• 15.S: Oxidation and Reduction Reactions (Summary)