EBK ORGANIC CHEMISTRY-PRINT COMPANION (
EBK ORGANIC CHEMISTRY-PRINT COMPANION (
4th Edition
ISBN: 9781119776741
Author: Klein
Publisher: WILEY CONS
Question
Book Icon
Chapter 20, Problem 35PP
Interpretation Introduction

Interpretation:

The given set of compounds should be arranged in their increasing acidity order.

Concept introduction:

Acidity of the compound is the measure of strength of the acid.  If the acid forms a more stable conjugate base after deprotonation then that acid is said to be more acidic.  The number and the strength of electron withdrawing group attached to the carbon that bears the removable proton determine the acidity of compound.

Expert Solution & Answer
Check Mark

Answer to Problem 35PP

The ranking of the given set of compounds in increasing acidity order of (a) and (b) is,

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  1

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  2

Explanation of Solution

(a)

To find: The increasing acidity order for the given set of compounds.

Determine the acidic proton and electron withdrawing groups that is available

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  3

The centers that is highlighted in the above structures has the hydrogen which is more susceptible for deprotonations and delocalization. Because the electron withdrawing groups involve the delocalization step. Electron withdrawing groups stabilize the conjugate base while electron-donating groups destabilize the conjugate base. Substituents that are closer to the carboxylic acid have a greater affect on acidity.

Closer the electron withdrawing group more is the acidity and vice versa.

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  4

Each of these carboxylic acids is a para-substituted benzoic acids. The relative acid strength depends on the electron withdrawing or electron donating capacity of the substituent.

* Electron withdrawing groups pull electron density away from the ring, thus stabilizing the anionic charge on the conjugate base, thus giving a stronger acid.

* Electron donating groups donate electron density to the ring, thus stabilizing the anionic charge on the conjugate base, resulting a weaker acid.

The carboxylic acids are arranged in order of increasing acid strength.

*Methoxy and methyl groups are strongly and weakly electron donating respectively and bromine atom is weakly electron withdrawing.

*A carbonyl group and a nitro group in the given carboxylic acid is moderate and strong electron withdrawing groups respectively. deprotonated structure of the given carboxylic acid is drawn above. The more closer the electron withdrawing group to the carboxylate ion, the conjugate is more stabilized.  From this we can confirm that p-methoxybenzoic acid < p-methylbenzoic acid< p-bromobenzoic acid<p-acetylbenzoic acid<p-nitrobenzoic acid.

(b)

To find: The increasing acidity order for the given set of compounds.

Determine the acidic proton and electron withdrawing groups that is available

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  5

The centers that is highlighted in the above structures has the hydrogen which is more susceptible for deprotonations and delocalization. Because the electron withdrawing groups involve the delocalization step. Electron withdrawing groups stabilize the conjugate base while electron-donating groups destabilize the conjugate base. Substituents that are closer to the carboxylic acid have a greater affect on acidity.

Closer the electron withdrawing group more is the acidity and vice versa.

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  6

Each of these carboxylic acids is a bromine-substituted cyclopentanoic acids. The relative acid strength depends on the electron withdrawing or electron donating capacity of the substituent.

* Electron withdrawing groups pull electron density away from the ring, thus stabilizing the anionic charge on the conjugate base, thus giving a stronger acid.

* Electron donating groups donate electron density to the ring, thus stabilizing the anionic charge on the conjugate base, resulting a weaker acid.

The carboxylic acids are arranged in order of increasing acid strength.

*Bromine atom is a weakly electron withdrawing atom, it is closer to the carboxylic acid, the more it stabilizes the anionic charge on the conjugate base.

*The deprotonated structure of the given carboxylic acid is drawn above.  In the first structure the compound has the electron withdrawing group, namely bromine in this case is at γ position.  In the second structure the same bromine is at β position.  In the third structure the bromine is at α position.  The more closer the electron withdrawing group to the carboxylate ion, the conjugate is more stabilized. So the acidity order is 3-bromocyclopentanecarboxylic acid<2-bromocyclopentanecarboxylic acid < 1-bromocyclopentanecarboxylic acid.

Conclusion

Conclusion

The increasing order of acidity is ranked using the resonance structure of the formed conjugate base, and the order is

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  7

EBK ORGANIC CHEMISTRY-PRINT COMPANION (, Chapter 20, Problem 35PP , additional homework tip  8

Want to see more full solutions like this?

Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!

Chapter 20 Solutions

EBK ORGANIC CHEMISTRY-PRINT COMPANION (

Knowledge Booster
Background pattern image
Recommended textbooks for you
Text book image
Chemistry
Chemistry
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Cengage Learning
Text book image
Chemistry
Chemistry
ISBN:9781259911156
Author:Raymond Chang Dr., Jason Overby Professor
Publisher:McGraw-Hill Education
Text book image
Principles of Instrumental Analysis
Chemistry
ISBN:9781305577213
Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher:Cengage Learning
Text book image
Organic Chemistry
Chemistry
ISBN:9780078021558
Author:Janice Gorzynski Smith Dr.
Publisher:McGraw-Hill Education
Text book image
Chemistry: Principles and Reactions
Chemistry
ISBN:9781305079373
Author:William L. Masterton, Cecile N. Hurley
Publisher:Cengage Learning
Text book image
Elementary Principles of Chemical Processes, Bind...
Chemistry
ISBN:9781118431221
Author:Richard M. Felder, Ronald W. Rousseau, Lisa G. Bullard
Publisher:WILEY