The sex attractant of the common housefly is a hydrocarbon...

The sex attractant of the common housefly is a hydrocarbon with the formula $\mathrm{C}_{23} \mathrm{H}_{46} .$ On treatment with aqueous acidic $\mathrm{KMnO}_{4},$ two products are obtained, $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{12} \mathrm{CO}_{2} \mathrm{H}$ and $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{7} \mathrm{CO}_{2} \mathrm{H} .$ Propose a structure.

Key Concepts

Carbon Chain Nomenclature and Numbering

Correctly numbering the carbons in long-chain hydrocarbons is crucial for pinpointing substituent locations such as a double bond. In oxidative cleavage reactions, the carbon atoms at the cleavage site become part of the new carboxylic acid groups. By assigning numbers to the chain and comparing the lengths of the oxidation products, one can determine the position of the double bond in the original hydrocarbon.

Retrosynthetic Analysis from Oxidation Products

When a molecule undergoing oxidation gives two distinct carboxylic acids, their carbon counts provide clues to the location of the original double bond. By matching the numbers of carbons in the acids with the total number of carbons in the starting material, one can deduce how the alkene was partitioned during the oxidative cleavage, essentially working backwards from the products to propose the structure of the original molecule.

Degree of Unsaturation

Chemical formulas can be analyzed for degrees of unsaturation, which indicate the presence of rings or multiple bonds. For a hydrocarbon with the formula C23H46, the formula for a fully saturated alkane would be C23H48. The two missing hydrogen atoms signal a single degree of unsaturation, most commonly due to a carbon–carbon double bond, setting the stage for further structural deductions.

Oxidative Cleavage of Alkenes

Oxidative cleavage is a reaction in which strong oxidizing agents, such as aqueous acidic KMnO4, attack the double bond of an alkene to break it, converting the alkene carbons into carboxylic acid groups. In this process, each carbon of the former double bond typically transforms into a carboxyl group, which is key to interpreting product structure from observed acid fragments.

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