Page 14 - Geometry

Oxidation of alkene The oxidation of alkenes takes place in the presence of the strong oxidizing agent, acidified potassium manganate (VII) solution. However, depending on the concentration and temperature of the oxidizing agent, the final product of the oxidation can vary. Acidified potassium manganate (VII) is a light pink/pale purple solution. On mixing alkene with a dilute solution of acidified potassium manganate (VII) at room temperature, the oxidizing agent loses its color and becomes colorless, whereas the alkene in the solution turns into a diol. For example, when using ethene in these conditions, ethane-1,2-diol is produced. If the conditions are made harsher by using a concentrated solution of acidified potassium manganate (VII) at higher temperature, the double bond between the carbon atoms is broken completely. A diol is formed initially that is further oxidized to carboxylic acid, ketone, aldehyde, or carbon dioxide gas. The final product of the reaction depends upon the other groups attached to the double-bonded carbon atoms. The three reactions are summarized as, 1. If the double-bonded carbon is bonded with two hydrogen atoms, then it is oxidized into carbon dioxide. 2. If it is bonded with a hydrogen atom and an alkyl group, it is oxidized to aldehyde, which is further oxidized to a carboxylic acid. 3. Lastly, if the double-bonded carbon is bonded with two alkyl groups, then it is oxidized to a ketone. Polymerization in alkene Alkenes are the building blocks that are used to make polymer molecules. A polymer is a long molecule that is made up of a chain of smaller repeating units, called monomers. For example, ethene is polymerized to make polyethene which is primarily used to make plastic bags. This reaction is called addition polymerization because monomers are added together to form a polymer, and it is expressed using the displayed formula, where n is a large number. Page 13 of 20 Study Guide for Organic Chemistry