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Which Alkene Gives Acetone on Ozonolysis?

Ozonolysis is a powerful reaction in organic chemistry, widely used for cleaving double bonds in alkenes to yield various carbonyl compounds. A frequently asked question in the field of chemical analysis is: Which alkene gives acetone on ozonolysis? Understanding this reaction is critical for chemists, especially those involved in synthetic organic chemistry.

What is Ozonolysis?

Ozonolysis is a process that involves the reaction of an alkene with ozone (O₃) to break the carbon-carbon double bond. The reaction typically proceeds via the formation of an ozonide intermediate, which is then cleaved by a reductive workup, often using zinc (Zn) and acetic acid, to yield carbonyl compounds like aldehydes, ketones, or carboxylic acids depending on the alkene's structure.

Identifying the Alkene That Forms Acetone

When asking which alkene gives acetone on ozonolysis, we need to consider the structure of the alkene. Acetone, or propanone, has the molecular formula (CH₃)₂CO, meaning the alkene must have a structure that can split into two identical parts, each contributing a methyl group and a carbonyl group (C=O).

The alkene that fits this description is 2-butene (C₄H₈). Upon ozonolysis, 2-butene is cleaved at the double bond to form two molecules of acetone:

[ \text{CH}3-CH=CH-CH3 + O3 \rightarrow 2 \times \text{CH}3COCH_3 ]

This reaction occurs because the double bond in 2-butene is symmetrically located between the two central carbon atoms, which each have a methyl group attached. When the ozonide intermediate forms and subsequently breaks down, each of the central carbon atoms becomes part of an acetone molecule.

Other Alkenes and Their Ozonolysis Products

It is also useful to consider why other alkenes do not produce acetone upon ozonolysis. For instance:

• 1-Butene (CH₂=CHCH₂CH₃): Ozonolysis of 1-butene yields formaldehyde (CH₂O) and propanal (CH₃CH₂CHO), not acetone.
• 2-methylpropene (CH₂=C(CH₃)₂): Ozonolysis of this compound gives acetone and formaldehyde. However, the production of acetone here is due to the splitting of the carbon-carbon double bond adjacent to the tert-butyl group, not because the entire alkene yields acetone.

Thus, when considering which alkene gives acetone on ozonolysis, 2-butene stands out as the primary candidate, providing a direct and exclusive yield of acetone.

Conclusion

Understanding the specific conditions and outcomes of ozonolysis is essential for any chemist working with alkenes. The answer to which alkene gives acetone on ozonolysis is straightforward: 2-butene is the alkene that yields two molecules of acetone upon undergoing ozonolysis. This knowledge is crucial for those involved in the synthesis and analysis of organic compounds, particularly in optimizing reactions where acetone is a desired product.