Carboxylic acids contain the carboxyl (-COOH) functional group. They are weak acids because the carboxyl group only partially dissociates in water, existing in an equilibrium between ionized and un-ionized forms. The acidity or acid strength of a carboxylic acid is determined by its acidity constant (Ka), which indicates the level of dissociation into ions in solution. The Ka value depends on the structure of the carboxylic acid and any substituents that induce electron-withdrawing or electron-donating effects, which alter the stability and acid strength of the carboxyl group.

1. CARBOXYLIC ACID
ACIDITY OF
CARBOXYLIC ACID
BY SHUBHAM CARPENTER

2. Organic Compound which contain the carboxyl functional group (-COOH) are
Called the Carboxylic Acid.
General Formula –
• WHAT IS CARBOXYLIC ACID ?
Example :-

3. Now, We Come to Acidity of Carboxylic Acid -
Carboxylic Acid are Acidic In Nature, Thy Can Donate Proton and From
Salt On React With Bases.
• If, We Dissolve an Acid on Water, So,, the Acid is Proton Donor…..
‣ The Tendency to Loose Proton of an Acid is Termed as Acidity..
TERM ACIDITY
Hydronium Ion
Carboxylic Ion
work as Base

4.  ACIDITY CONSTANT -
Strong Acids (e.g., HCL or H2SO4) Completely Ionized in Aqueous Solutions
Whereas, Carboxylic Acids Are Weak acids. They are only partially ionized in
aqueous solution and an equilibrium exist Between the ionized and unionized
forms.
The Form of Ions On Reaction With Water Which Make This Process Reversible.
So, The Dissociation Constant is Also Known as Eq. Constant & Acidity Constant (Ka).
Ionized
Ionized
Un-Ionized
Un-Ionized
The Acidity Constant Shows The Acidic Strength Of Carboxylic Acid. Higher The Value of
Ka Higher is Acidic Strength.

5. Pka = -logKa
 EXAMPLE :-
ACETIC ACID CHLOROACETIC ACID FLUOROACETIC ACID
Pka-4.8 Pka-2.8 Pka-2.6
<
<
FORMIC ACID PROPANOIC ACID
ACETIC ACID
< <

6.  EXPLAINATION OF ACIDITY -
Why Carboxylic acid are more Acidic than Alcohol and Phenol ?
ALCOHOL
PHENOL
ACIDIC
STRENGTH
CARBOXYLIC
ACID
On Alcohol, alkyl Show Inductive Effect It Means That alkyl Give More Negative
Charge to it.
Whereas, In Phenol, It Shows Resonance Effect So, It is More Acidic Then Alcohol, But
Carbon are capable of Carry Less –ve Charge on it..
ACIDIC
STRENGTH

7. But, In Carboxylic Acid, It Also Shows Resonance But O is Sufficient to Carry More
Negative Charge. So it Can transfer Bond Oxygen to Oxygen.
Partially Negative
Resonance Effect – In Which Atom-Atom Bond (Double Bond) Shifted to Another
For Stability on Lose of Hydrogen Ion.

8.  EFFECT OF SUBSTITUENTS ON ACIDITY -
The Most Important Factor Affecting The Acidity Is The Inductive Effect Of
Substituent's On The Alpha Carbon
# INDUCTIVE EFFECT –
The Carboxylic acid Bonded Alkyl Group show inductive effect - +I and –I
Effect on Alkyl group Which Show the Electron Donor and Acceptor to
Manage Oxygen Stability.
Manage Oxygen Stability.
+I
-I
EWG
EDG
Electron Donating Group – Those Who Donate Electron to –COOH Group.
• Increase –ve Charge on Oxygen.
• Which Decrease Stability.
• Decrement In Acidic Strength.
EXAMPLES
EXAMPLES
Alkyl group, OH, NH2

9. Electron Withdrawing Group – Those Who Accept Electron from –COOH Group.
• Decrease –ve Charge on Oxygen.
• Which Increase Stability.
• Increment In Acidic Strength.
EXAMPLES
EXAMPLES
Cl, Br, F, CN
UNDERSTAND WITH EXAMPLE -
> >
Trichloroacetic Acid Trichloroacetic Acid Trichloroacetic Acid
> >
Butanoic acid Propanoic Acid Acetic Acid
>
>

10. >
Distance of EDG & EWG also
affect the Acidity of
Carboxylic Acid
 IDENTIFY EWG & EDG
 IDENTIFY EWG & EDG
If Y is More –ve then X –
EWG
If X is more –ve then Y –
EDG
>
EDG
• EXAMPLE
ELECTRON
WITHDRAWING GROUP