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Ch.8 - Reactions of Alkenes
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 8, Problem 62

The sex attractant of the housefly has the formula C23H46. When treated with warm potassium permanganate, this pheromone gives two products: CH3(CH2)12COOH and CH3(CH2)7COOH. Suggest a structure for this sex attractant. Explain which part of the structure is uncertain.

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Step 1: Analyze the given information. The sex attractant has the molecular formula C23H46, and upon oxidation with warm potassium permanganate, it produces two carboxylic acids: CH3(CH2)12COOH and CH3(CH2)7COOH. This suggests that the original molecule contains a double bond that is cleaved during the oxidation reaction.
Step 2: Recall the mechanism of oxidative cleavage of alkenes by potassium permanganate. When an alkene is treated with warm KMnO4, the double bond is broken, and each carbon of the double bond is converted into a carboxylic acid group if it is bonded to hydrogen atoms. This indicates that the sex attractant contains a double bond in its structure.
Step 3: Deduce the positions of the double bond based on the products formed. The two carboxylic acids produced have chain lengths of 13 carbons (CH3(CH2)12COOH) and 8 carbons (CH3(CH2)7COOH). This implies that the double bond is located between the 13th and 14th carbon atoms in the original C23H46 molecule.
Step 4: Propose a structure for the sex attractant. Based on the cleavage pattern, the molecule likely has a long hydrocarbon chain with a single double bond between the 13th and 14th carbons. The structure can be represented as CH3(CH2)12CH=CH(CH2)7CH3.
Step 5: Address the uncertainty in the structure. The exact stereochemistry (cis or trans configuration) of the double bond is not specified in the problem. This is an important aspect of the structure that remains uncertain and would require additional experimental data, such as spectroscopic analysis, to determine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Formula Interpretation

The molecular formula C23H46 indicates that the compound consists of 23 carbon atoms and 46 hydrogen atoms. This formula suggests that the compound is likely a long-chain hydrocarbon, possibly with functional groups. Understanding how to interpret molecular formulas is crucial for deducing the structure and properties of organic compounds.
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Oxidation Reactions

The reaction with warm potassium permanganate indicates an oxidation process, where the alkene or alkane is converted into carboxylic acids. The products, CH3(CH2)12COOH and CH3(CH2)7COOH, suggest that the original compound likely contained double bonds or branched structures that were oxidized. Recognizing the types of reactions and their outcomes is essential for predicting product structures.
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Structural Isomerism

The presence of two different carboxylic acids as products implies that the original sex attractant may have structural isomers. Structural isomerism occurs when compounds have the same molecular formula but different arrangements of atoms. Identifying which part of the structure is uncertain involves analyzing where the double bonds or branching may exist, leading to different isomeric forms.
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Related Practice
Textbook Question

Cyclohexene is dissolved in a solution of lithium chloride in chloroform. To this solution is added one equivalent of bromine. The material isolated from this reaction contains primarily a mixture of trans-1,2-dibromocyclohexane and trans-1-bromo-2-chlorocyclohexane. Propose a mechanism to show how these compounds are formed.

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Textbook Question

The two butenedioic acids are called fumaric acid (trans) and maleic acid (cis). 2,3-Dihydroxybutanedioic acid is called tartaric acid.

Show how you would convert

a. fumaric acid to (±)-tartaric acid.

b. fumaric acid to meso-tartaric acid.

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Textbook Question

One of the constituents of turpentine is α-pinene, formula C10H6. The following scheme (called a “road map”) gives some reactions of α-pinene. Determine the structure of α-pinene and of the reaction products of A through E.

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Textbook Question

In contact with a platinum catalyst, an unknown alkene reacts with three equivalents of hydrogen gas to give 1-isopropyl-4-methylcyclohexane. When the unknown alkene is ozonized and reduced, the products are the following:

Deduce the structure of the unknown alkene.

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Textbook Question

Unknown X, C5H9Br does not react with bromine or with dilute KMnO4. Upon treatment with potassium tert-butoxide, X gives only one product, Y, C5H8. Unlike X, Y decolorizes bromine and changes KMnO4 from purple to brown. Catalytic hydrogenation of Y gives methylcyclobutane. Ozonolysis–reduction of Y gives dialdehyde Z, C5H8O2. Propose consistent structures for X, Y, and Z. Is there any aspect of the structure of X that is still unknown?

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Textbook Question

Propose a mechanism for the following reaction.

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