Why carboxylic acids are more acidic than phenols?

Question

Accepted Answer

Carboxylic acids are acidic due to resonance stabilization of carboxylate anion and in phenols, acidic character is present due to resonance stabilization of phenoxide anion. Carboxylic acid are more acidic than phenols because the negative charge in carboxylate anion is more spread out as compared to the phenoxide ion as there are two electronegative O-atoms in carboxylate anion in comparison to one in phenoxide ion. In the resosnce structures of carboxylate anion, the negative charge is present on the O-atoms while in resonance of phenoxide ion negative charge is also present on electropositive carbon atom, which leads to less stability of phenoxide ion than carboxylate anion.

Answer

Though both carboxylate nd phenoxide ion undergoes resonance.. bt in carboxylate ion the delocalisation of -ve charge is from 1 oxygen to the other i.e. equivalent structures r obtained.... While in phenoxide ion, delocalisation of-ve charge is from oxygen atom to less electronegative carbon atomThus stability of carboxylate ion increases.. nd hence carboxylic acids r more acidic then phenols.

Answer

Introduction:
Carboxylic acids and phenols are both organic compounds that contain acidic functional groups. However, carboxylic acids are generally more acidic than phenols. This can be attributed to several factors that influence the strength of their respective acidic properties.

1. Structure:
The structure of the acidic functional group in carboxylic acids and phenols plays a crucial role in determining their acidity. Carboxylic acids contain a carboxyl group (-COOH), which consists of a carbonyl group (C=O) and a hydroxyl group (OH) bonded to the same carbon atom. Phenols, on the other hand, contain a hydroxyl group (-OH) directly bonded to an aromatic ring. The presence of the carbonyl group in carboxylic acids leads to the delocalization of the negative charge between the oxygen atoms, making the carboxylate ion more stable. This stabilization of the conjugate base enhances the acidic character of carboxylic acids.

2. Resonance:
Carboxylic acids exhibit resonance stabilization due to the delocalization of electrons within the carboxyl group. The lone pair of electrons on the oxygen atom of the hydroxyl group can resonate with the pi electrons of the adjacent carbonyl group, resulting in a resonance structure. This delocalization of electrons increases the stability of the carboxylate ion, making it more acidic. In contrast, phenols do not exhibit significant resonance stabilization, as the lone pair of electrons on the oxygen atom is primarily localized on the hydroxyl group.

3. Inductive Effect:
The inductive effect refers to the electron-withdrawing or electron-donating nature of nearby functional groups or substituents. Carboxylic acids possess a highly electronegative carbonyl group, which withdraws electron density from the adjacent hydroxyl group, thus increasing the acidity. In phenols, the electron-donating nature of the aromatic ring decreases the acidity by destabilizing the phenoxide ion.

4. Hydrogen Bonding:
Carboxylic acids can form intermolecular hydrogen bonds due to the presence of the hydroxyl group and the carbonyl group. This enhances their ability to donate a proton, making them more acidic. Phenols, although capable of forming intramolecular hydrogen bonds, do not exhibit strong intermolecular hydrogen bonding, resulting in weaker acidity compared to carboxylic acids.

Conclusion:
In summary, carboxylic acids are more acidic than phenols due to their structure, resonance stabilization, inductive effect, and hydrogen bonding ability. The presence of the carbonyl group, resonance delocalization, electron-withdrawing nature, and hydrogen bonding interactions contribute to the enhanced acidity of carboxylic acids. Understanding these factors helps in explaining the relative acidity of carboxylic acids and phenols.

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Why carboxylic acids are more acidic than phenols.?

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