Redox reactions, or oxidation-reduction reactions, are fundamental processes in both general and organic chemistry, characterized by the transfer of electrons between reactants. In general chemistry, these reactions are defined by the movement of electrons, while in organic chemistry, the focus shifts to changes in the number of oxygen and hydrogen atoms within a molecule.
Oxidation in organic chemistry is defined as the increase in carbon-oxygen bonds, whereas reduction is characterized by an increase in carbon-hydrogen bonds. For instance, when considering the transformation of hydrocarbons, we can observe the oxidation process starting from methane, a simple hydrocarbon, progressing through various stages to carbon dioxide. However, the key transformations relevant to organic chemistry occur between alcohols, aldehydes, and carboxylic acids.
In the oxidation pathway, a hydrocarbon can be oxidized to form an alcohol, marking the introduction of the first carbon-oxygen bond. As the oxidation continues, the alcohol can be further oxidized to an aldehyde or ketone, resulting in the formation of a second carbon-oxygen bond. Continuing this process leads to the formation of a carboxylic acid, which contains three carbon-oxygen bonds. If oxidation were to proceed further, carbon dioxide would be produced, which contains four carbon-oxygen bonds, but this is outside the scope of typical organic reactions.
Conversely, during reduction, the process begins with a carboxylic acid, which can be reduced to an aldehyde or ketone, decreasing the number of carbon-oxygen bonds from three to two. This reduction also increases the number of carbon-hydrogen bonds, moving from one bond in the carboxylic acid to two in the aldehyde or ketone. Further reduction leads to the formation of an alcohol, which has three carbon-hydrogen bonds. The focus remains on the transformations between alcohols, aldehydes, and carboxylic acids, as these are the key organic molecules involved in redox reactions.
