Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 20: Problem 484

(a) While many \(\alpha, \beta\) -unsaturated carboxylic acids undergo decarboxylation upon heating, the \(\alpha, \beta\) -unsaturated acid shown below is immune to such a reaction. What does this suggest about the mechanism of decarboxylation of \(\alpha, \beta-\) unsaturated acids?

Short Answer

Expert verified
The given α, β-unsaturated carboxylic acid cannot undergo decarboxylation due to steric hindrance caused by the two methyl groups present at the β-carbon, which prevents the necessary 6-membered cyclic transition state and [3,3]-sigmatropic rearrangement for the reaction to proceed. This suggests that the mechanism of decarboxylation for α, β-unsaturated carboxylic acids depends on a specific structural arrangement which enables a [3,3]-sigmatropic rearrangement via a 6-membered cyclic transition state.

Step by step solution

01

Recognize the structure of the given compound

The given compound is an α, β-unsaturated carboxylic acid, which means it has a carbon-carbon double bond between alpha (α) and beta (β) carbons and has a carboxylic acid functional group. The given molecule has the structure: ``` H3C-C(CH3)=C-COOH ```
02

Understand the mechanism of decarboxylation in α, β-unsaturated carboxylic acids

For an α, β-unsaturated carboxylic acid to undergo decarboxylation, it needs to proceed through a 6-membered cyclic transition state via a [3,3]-sigmatropic rearrangement. This transition state involves the breaking of the C-C bond between the carbonyl carbon and the α-carbon and the formation of a new C-C bond between the α-carbon and another carbon atom in the molecule. The rearrangement results in the loss of a carboxyl group (COOH) as carbon dioxide (CO2) and the formation of a new π-bond between the α- and the γ-carbon, leading to the formation of an alkene.
03

Identify the factors that prevent the given molecule from undergoing decarboxylation

The reaction cannot proceed via the 6-membered cyclic transition state, as there is no possible interaction between α-carbon and another carbon atom in the molecule for the formation of a new C-C bond. This is due to the steric hindrance caused by the two methyl groups present at the β-carbon. These two methyl groups effectively block the approach of the α-carbon to any other carbon atom in the molecule, and prevent the necessary rearrangement to take place. Considering these structural features, it becomes clear that the mechanism of decarboxylation in this particular α, β-unsaturated carboxylic acid is not possible, which indicates that the molecule cannot undergo decarboxylation upon heating.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

4-Bromobicyclo \([2,2,2]\) octane-1-carboxylic acid is more acidic than 5 -bromopentanoic acid. Explain this observation by considering the transmission of the electrical effect of the C-Br dipole.

Predict the outcome of an attempted esterification of acetic acid with t-butyl alcohol in the presence of dry \(\mathrm{HCl}\).

Draw structures for the following compounds. (a) a-aminopropionic acid (alanine) (b) vinylacetic acid (c) para-methoxybenzoic acid

Synthesize butyric acid from any organic compound, using inorganic reagents.

For each of the following pairs tell which acid is the stronger and why: (a) \(\mathrm{CH}_{3}-\mathrm{COOH}\) or \(\mathrm{H}-\mathrm{COOH}\) (b) \(\mathrm{CH}_{3}-\mathrm{COOH}\) or \(\mathrm{CL}-\mathrm{CH}_{2}-\mathrm{COOH}\) (c) \(\mathrm{F}-\mathrm{CH}_{2}-\mathrm{COOH}\) or \(\mathrm{Br}-\mathrm{CH}_{2}-\mathrm{COOH}\) (d) \(\mathrm{CL}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}\) or \(\mathrm{CH}_{3}-\mathrm{CHCL}-\mathrm{COOH}\) (e) \(\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{OH}\) or \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{OH}\) (f) \(\mathrm{CH}_{3}-\mathrm{OH}\) or \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{COOH}\)
See all solutions

Recommended explanations on Chemistry Textbooks

Chemical Reactions

Read Explanation

Physical Chemistry

Read Explanation

Inorganic Chemistry

Read Explanation

Kinetics

Read Explanation

Chemical Analysis

Read Explanation

Ionic and Molecular Compounds

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free