Intermediate Level Carboxylic Acids
Properties
Solubility
The solubility of carboxylic acids in water is quite high, especially for short chained acids, since they would have Hydrogen bonding.
Dimerisation
Carboxylic acids tend to dimerise in water since they can Hydrogen bond with themselves.
Acidity
The acidity of carboxylic groups increases with the introduction of alpha electron withdrawing groups, while it decreases with the introduction of alpha electron donating groups.
| pKa | |
| HCOOH | 3.75 |
| CH3COOH | 4.76 |
| CH2ClCOOH | 2.86 |
| CHCl2COOH | 1.29 |
| CCl3COOH | 0.65 |
Preparation
Oxidation of alcohols
Primary and alcohols can be oxidised to prepare carboxylic acids.
Ozonolysis
Ozonolysis cleaves the double bond to produce carboxylic acids if no reducing agents are used.
Nitriles
Hydrolysis of nitriles under acid conditions produces the acids
Hydrolysis of acid derivatives
All acid derivatives give off the acid when reacted with water. These will be discussed in latter chapters
Reactions
Bases
Like all acids, carboxylic acids react with bases and metals as an acid/base reaction. The reaction with Sodium carbonate can be used to distinguish between carboxylic acids and alcohols.
Reduction
Carboxylic acids can be reduced to primary alcohols using LiAlH4 in ether.
Decarboxylation
This is a reaction which can be used to reduce the carbon chain by 1 by fusing the carboxylic acid with sodium hydroxide. The functional group will be lost.
Halogenation
A simple reaction to add Cl to the carboxylic acid on the alpha Carbon. This can be used to:
Increase acidity
Introduce another functional group
Preparation of Acid derivatives
All acid derivatives can be formed from carboxylic acids. These will be described in latter chapters.