Explain: Ozonlysis of alkenes
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Answer:
Ozonolysis is an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone. Alkenes and alkynes form organic compounds in which the multiple carbon–carbon bond has been replaced by a carbonyl group while azo compounds form nitrosamines.
Explanation:
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Answer:
Alkenes can undergo ozonolysis to form alcohols, aldehydes, ketones, or carboxylic acids. The general procedure uses a solution of alkene in methanol. Ozone is bubbled through this solution at approximately 780 Celsius. When the solution turns blue, the alkene is consumed (the blue colour comes from the unreacted ozone). Other indicators of the endpoint of the reaction include potassium iodide solution. For this indicator, a stream of ozone enriched oxygen is bubbled through a mixture of the reactants. The gas that bubbles out is channeled through a solution of potassium iodide. Once the reaction is complete and there is no more alkene left to react with the ozone, the gas goes on to oxidize potassium iodide to iodine. The reaction of potassium iodide with ozone to give iodine is indicated by the distinct violet colour of iodine.
Once the ozone is added to the reaction mixture, a reagent must be added to convert the ozonide to the required carbonyl derivative. For this conversion, 2 techniques can be employed:
- Reductive Workup
- Oxidative Workup
However, reductive workup conditions see a lot more use when compared to oxidative workup conditions. In these workup conditions, triphenylphosphine, thiourea, zinc dust, and dimethyl sulfide can be used to produce aldehydes or ketones. On the other hand, hydrogen peroxide can be used to produce carboxylic acids. Ozone can also be employed to oxidize other functional groups such as benzyl ethers. Pyridine is also used to buffer the reaction since small amounts of acid may be generated at the time of reaction. A 1:1 ratio of solvent with dichloromethane co-solvent facilitates the timely cleavage of the ozonide. Ozonolysis of oleic acid is used to produce azelaic acid and pelargonic acid on an industrial scale.