Explain, why phenols are more acidic than alcohols ?
**Introduction:**
Phenols and alcohols are two classes of organic compounds containing a hydroxyl group (-OH). However, phenols are more acidic than alcohols due to the presence of an aromatic ring in phenols and the resonance stabilization it provides to the negative charge on the oxygen atom.
**Electronic Effects:**
- The electron-withdrawing nature of the aromatic ring in phenols enhances the acidity of the compound.
- The conjugation of the benzene ring with the oxygen atom in phenols stabilizes the negative charge, making it easier to remove a proton.
- In alcohols, the presence of an alkyl group attached to the hydroxyl group decreases the acidity as alkyl groups are electron-donating in nature and destabilize the negative charge.
**Resonance Stabilization:**
- Phenols possess a resonance structure where the negative charge can be delocalized over the entire benzene ring. This resonance stabilization makes it easier to remove a proton and increases the acidity.
- Alcohols lack this resonance stabilization, as the oxygen atom is not attached to an aromatic ring. Therefore, the negative charge is localized on the oxygen atom, making it more difficult to remove a proton.
**Effect of Inductive Effects:**
- The inductive effect refers to the electron-donating or electron-withdrawing nature of substituents attached to the phenol or alcohol molecule.
- In phenols, if electron-withdrawing groups like -NO2 or -Cl are present, they pull electron density away from the oxygen atom, further increasing the acidity.
- In alcohols, the inductive effect of alkyl groups is usually electron-donating, which decreases the acidity.
**Hydrogen Bonding:**
- Phenols can form intermolecular hydrogen bonds due to the presence of the -OH group attached to an aromatic ring.
- Alcohols can also form hydrogen bonds, but the presence of an aromatic ring in phenols makes the hydrogen bonding in phenols stronger.
- The stronger hydrogen bonding in phenols contributes to their increased acidity compared to alcohols.
In conclusion, phenols are more acidic than alcohols due to the electron-withdrawing and resonance effects of the aromatic ring, which stabilize the negative charge on the oxygen atom. Additionally, the presence of stronger intermolecular hydrogen bonding in phenols further enhances their acidity.
Explain, why phenols are more acidic than alcohols ?
Alcohols and Phenols
Phenol is more acidic than cyclohexanol and acyclic alcohols because the phenoxide ion is more stable than the alkoxide ion. ... However, in a phenoxide ion, the negative charge is delocalized over the benzene ring; that is, it is resonance-stabilized.
Phenol is more acidic than alcohols due to stabilisation of phenoxide ion through resonance. Presence of electron withdrawing group increases the acidity of phenol by , stabilising phenoxide ion while presence of electron releasing group decreases the acidity of phenol by destabilising phenoxide ion.