Chemistry > Carboxylic Acids and Derivatives > 4.0 Chemical Properties of Carboxylic Acid
Carboxylic Acids and Derivatives
1.0 Nomenclature
2.0 General Methods of Preparation
3.0 Physical Properties of Carboxylic Acid
4.0 Chemical Properties of Carboxylic Acid
5.0 Ortho Effect
6.0 Reaction Involving Cleavage of —OH Group
6.1 Esterification
6.2 Formation of acid chloride
6.3 Formation of Acid Anhydride
6.4 Formation of Amides
7.0 Reaction Involving —COOH Group
8.0 Hell-Volhard-Zelinsky Reaction
9.0 Heating of Dicarboxylic Acids
10.0 Abnormal Behaviour of Formic Acid
11.0 Derivatives of Carboxylic Acid
12.0 Relative Reactivity of Acid Derivatives
13.0 Resonance Effect
14.0 Acyl Chloride RCOCl
15.0 Amides
16.0 Ester (RCOOR)
17.0 Acid Anhydrides
18.0 Method of Preparation
18.1 Acylation
18.2 Sodium salt of carboxylic acids also react with acyl chlorides to give
18.3 Cyclic anhydrides
18.4 Chemical Properties
4.2 Effect of substituents on Acidity
6.2 Formation of acid chloride
6.3 Formation of Acid Anhydride
6.4 Formation of Amides
18.2 Sodium salt of carboxylic acids also react with acyl chlorides to give
18.3 Cyclic anhydrides
18.4 Chemical Properties
Any factor that stabilizes the anion more than it stabilizes the acid should increase the acidity and any factor that makes the anion less stable should decrease the acidity of the carboxylic acid.
(a) An electron withdrawing substituent stabilizes the anion by dispersing the $–ve$ charge and therefore increases the acidity of carboxylic acid.
(b) Electron releasing substituetns intensify the $–ve$ charge on the anion resulting in decrease of stability of the carboxylate anion and therefore decreases the acidity of the acid.
Carboxylic acids are weak acids and their carboxylate ions are strong conjugate bases are slightly alkaline due to the hydrolysis of carboxylate anion compared to other species. The order of acidity and basicity of corresponding conjugate bases ar as follow.
Acidity— $RCOOH\; > \;HOH\; > \;ROH\; > \;CH \equiv CH > N{H_3} > RH$
Basicity— $RCO{O^--} < O{H^--} < HC \equiv {C^--} < NH_2^-- < {R^--}$
The effect of various, numberous and their distance from the carboxylic group has been illustrated with the help of following examples.
(i) The effect of number of the substituent is shown by the chloro substituted acetic acids. The acid strength increases in the order given below.
The increase in the no. of chloro substituent on $\alpha $-carbon atom of acetic acid make the electron withdrawing effect more pronounced and hence make carboxylate ion more stable.
When electron releasing substituent is attached to the carboxylic group then acid strength decreases as the electron releasing power increases.
(ii) The effect of nature of the substituent is illustrated by the various halo acetic acids. Their acid strength follows the order
(iii) Effect of the position of the substituent: The effect of the substituent decreases as its distances from $—COOH$ group increases.
