Draw the structure of an eight-carbon alkene that would yield the following compound (and no others) after treatment with ozone followed by dimethyl sulfide.
The correct answer and explanation is :
To determine the structure of the eight-carbon alkene that yields a specific compound after treatment with ozone followed by dimethyl sulfide (DMS), we need to consider the reaction mechanism and the properties of ozonolysis.
Ozonolysis of Alkenes:
When an alkene undergoes ozonolysis, the double bond breaks, and two carbonyl-containing fragments (either aldehydes or ketones) are formed. The reaction proceeds as follows:
- Ozone (O₃) adds to the carbon-carbon double bond, forming a highly reactive intermediate known as an ozonide.
- The ozonide then undergoes cleavage, producing two carbonyl-containing compounds (usually aldehydes or ketones).
- In the case of dimethyl sulfide (DMS) being used to work up the reaction, DMS reduces the ozonide intermediate, resulting in the formation of the carbonyl-containing products.
For this question, we’re asked to determine the structure of an eight-carbon alkene. The key here is that ozonolysis will break the alkene into two smaller carbonyl compounds, and the treatment with dimethyl sulfide will not change these products, only reduce the ozonide intermediate.
Structure of the Alkene:
The alkene must be constructed so that its ozonolysis generates only one set of carbonyl compounds, meaning the cleavage of the double bond should yield identical carbonyl fragments.
One possible structure for the alkene is 4-octene. The structure of 4-octene is:
- A straight-chain eight-carbon alkene with the double bond located between carbon atoms 4 and 5.
The reaction of 4-octene with ozone will cleave the double bond at positions 4 and 5, yielding two identical aldehyde fragments (each containing a 4-carbon chain with a formyl group), specifically pentanal (C₅H₁₀O). This is the only product formed after treatment with ozone followed by dimethyl sulfide, as the reaction will not form other aldehydes or ketones.
Thus, the correct answer is 4-octene, and it would yield pentanal after ozonolysis and work-up with dimethyl sulfide. The final structure of the compound is consistent with this mechanism.
