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Chapter 19: Carboxylic Acids

Summary | Carboxylic Acids | Preparations Carboxylic Acids | Reactions of Carboxylic Acids | Spectroscopic Analysis | Self Assessment | Quiz |

Reactions of Carboxylic Acids

Chapter  19: Carboxylic Acids

Carboxylation of Grignard Reagents

Grignard reaction with CO2 to give Carboxylic acids
(R = alkyl, aryl or vinyl)

Reaction type:  Oxidative Insertion then Nucleophilic Addition


Preparation of Carboxylic Acid Derivatives

conversion of carboxylic acids to derivatives
acyl chlorides
acid anhydrides

Reaction type:  Nucleophilic Acyl Substitution


Study Tip:
Disconnect carboxylic acids derivatives back to the parent acid plus the related component.
For example, an ester to the acid plus the alcohol: typical disconnection for an ester


Preparation of Acyl Chlorides

preparation of acyl chlorides

Reaction type:  Nucleophilic Acyl Substiution


Related Reactions

Preparation of Acid Anhydrides

preparation of acid anhydrides
Reaction type:  Nucleophilic Acyl Substitution


Preparation of Esters

esterification of carboxylic acids
Reaction type:  Nucleophilic Acyl Substitution


Study Tip:
The carboxylic acid and alcohol combination used to prepare an ester are reflected by the name of the ester,
e.g. ethyl acetate (or ethyl ethanoate), CH3CO2CH2CH3  can be made from CH3CO2H, acetic acid (or ethanoic acid) and HOCH2CH3 (ethanol).
This general "disconnection" is shown below:
disconnecting esters

Step 1:
An acid/base reaction. Protonation of the carbonyl makes it more electrophilic.
acid cat. esterification
Step 2:
The alcohol O functions as the nucleophile attacking the electrophilic C in the C=O, with the electrons moving towards the oxonium ion, creating the tetrahedral intermediate.
Step 3:
An acid/base reaction. Deprotonate the alcoholic oxygen.
Step 4:
An acid/base reaction. Need to make an -OH leave, it doesn't matter which one, so convert it into a good leaving group by protonation.
Step 5:
Use the electrons of an adjacent oxygen to help "push out" the leaving group, a neutral water molecule.
Step 6:
An acid/base reaction. Deprotonation of the oxonium ion reveals the carbonyl in the ester product.


Preparation of Amides

preparation of amides from carboxylic acids
Reaction type:  Nucleophilic Acyl Substiution


the protonation problem
Study Tip: Even though "acid + amine" is not a good synthetic method, it at least puts you on the right track.

Related Reactions

Reduction of Carboxylic Acids

reduction of carboxylic acids using LiAlH4
Reaction usually in Et2O or THF followed by H3O+ work-ups
Reaction type:  Nucleophilic Acyl Substitution then Nucleophilic Addition


Related Reactions

a-Halogenation (Hell-Volhard-Zelinsky reaction)

alpha-bromination of carboxylic acids
Reaction type: Substitution
Related Reactions


decarboxylation removes CO2
Reaction type: Elimination


malonic acid
Step 1:
Remember curly arrows flow.... Start at the protonation of the carbonyl, break the O-H bond and form the p bond, break the C-C and make the C=C. Note the concerted nature of this reaction and the cyclic transition state.
decarboxylation of malonic acid
Step 2:
Tautomerization of the enol of the carboxylic acid leads to the acid product (not shown here).


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