Skip to main content
Ch.8 - Reactions of Alkenes
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.8 - Reactions of AlkenesProblem 63
Chapter 8, Problem 63

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:
Ozonolysis reaction products of an alkene with carbonyl groups shown.
Deduce the structure of the unknown alkene.

Verified step by step guidance
1
Step 1: Analyze the hydrogenation reaction. The unknown alkene reacts with three equivalents of hydrogen gas in the presence of a platinum catalyst to form 1-isopropyl-4-methylcyclohexane. This indicates that the unknown alkene contains three double bonds, and the hydrogenation converts all double bonds into single bonds.
Step 2: Examine the ozonolysis products. Ozonolysis cleaves double bonds in alkenes, producing carbonyl compounds. The products shown in the images include formaldehyde (HCHO), acetone ((CH3)2CO), and two molecules of methylglyoxal (CH3COCHO). This suggests the positions of the double bonds in the unknown alkene.
Step 3: Deduce the connectivity of the unknown alkene. The presence of formaldehyde indicates a terminal double bond, while acetone and methylglyoxal suggest internal double bonds. The structure must align with the formation of these specific ozonolysis products.
Step 4: Consider the cyclic structure. The hydrogenation product, 1-isopropyl-4-methylcyclohexane, is a cyclohexane derivative. This implies that the unknown alkene is a cyclic compound with three double bonds distributed in a way that matches the ozonolysis products.
Step 5: Propose the structure of the unknown alkene. Based on the ozonolysis products and the hydrogenation result, the unknown alkene is likely 1-isopropyl-4-methylcyclohexa-1,3,5-triene, a cyclic triene with double bonds at positions 1, 3, and 5.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
8m
Was this helpful?

Key Concepts

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

Hydrogenation of Alkenes

Hydrogenation is the process of adding hydrogen (H2) to an alkene, which results in the conversion of the double bond into a single bond. This reaction typically requires a catalyst, such as platinum, to proceed efficiently. In this case, the unknown alkene reacts with three equivalents of hydrogen, indicating that it has at least one double bond that can be fully saturated.
Recommended video:
Guided course
00:48
The definition of hydrogenation.

Ozonolysis

Ozonolysis is a reaction where an alkene is treated with ozone (O3) followed by a reducing agent, leading to the cleavage of the double bond and the formation of carbonyl compounds (aldehydes or ketones). The products shown in the image are indicative of the ozonolysis reaction, which helps deduce the structure of the original alkene by analyzing the resulting carbonyl compounds.
Recommended video:
Guided course
06:30
General properties of ozonolysis.

Cycloalkanes and Substituents

Cycloalkanes are saturated hydrocarbons that contain carbon atoms arranged in a ring structure. The product mentioned, 1-isopropyl-4-methylcyclohexane, suggests that the unknown alkene likely has a structure that allows for the formation of this specific cycloalkane upon hydrogenation. Understanding the positioning of substituents on the cycloalkane is crucial for deducing the original alkene's structure.
Recommended video:
Guided course
01:11
How to find the root name for cycloalkanes
Related Practice
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.

1
views
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.

1
views
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

b. fumaric acid to meso-tartaric acid.

1
views
Textbook Question

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.

1
views
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?

Textbook Question

Propose a mechanism for the following reaction.

1
views