Phenol, p-Methylphenol, m-Nitrophenol and p-Nitrophenol follows order of increasing acidic strength

Question

The most suitable reagent for the conversion of \( \text{R-CH}_2\text{-OH} \) to \( \text{R-CHO} \) is:

Answer 1

To determine the order of increasing acidic strength among Phenol, p-Methylphenol, m-Nitrophenol, and p-Nitrophenol, we need to understand how different substituents affect the acidic strength of phenolic compounds.

Acidity of Phenolic Compounds: The acidity of phenolic compounds is influenced by substituents on the aromatic ring. Electron-withdrawing groups (EWG) increase acidity by stabilizing the phenoxide ion, while electron-donating groups (EDG) decrease acidity by destabilizing the phenoxide ion.
Analysis of Substituents:
- Phenol (C₆H₅OH): The reference compound with no additional substituent influence.
- p-Methylphenol (p-Cresol): The methyl group is an electron-donating group, which decreases the acidity of phenol by destabilizing the phenoxide ion.
- m-Nitrophenol: The nitro group is a strong electron-withdrawing group. Its meta-position moderately stabilizes the phenoxide ion, increasing acidity compared to phenol.
- p-Nitrophenol: The nitro group at the para position strongly withdraws electrons, providing more stabilization to the phenoxide ion compared to when the nitro group is at the meta position, thus making it more acidic than m-Nitrophenol.
Order of Acidic Strength: Based on the above analysis, the increasing order of acidic strength is:
- p-Methylphenol: Least acidic due to the electron-donating effect of the methyl group.
- Phenol: Moderate acidity as the reference compound.
- m-Nitrophenol: More acidic than phenol due to electron withdrawal by the nitro group.
- p-Nitrophenol: Most acidic due to the strong electron-withdrawing effect of the nitro group at the para position.
Conclusion: Therefore, the correct order of increasing acidic strength is: p\text{-}Methylphenol \lt Phenol \lt m\text{-}Nitrophenol \lt p\text{-}Nitrophenol.

Answer 2

To determine the order of increasing acidic strength among Phenol, p-Methylphenol, m-Nitrophenol, and p-Nitrophenol, we need to understand how different substituents affect the acidic strength of phenolic compounds.

Acidity of Phenolic Compounds: The acidity of phenolic compounds is influenced by substituents on the aromatic ring. Electron-withdrawing groups (EWG) increase acidity by stabilizing the phenoxide ion, while electron-donating groups (EDG) decrease acidity by destabilizing the phenoxide ion.
Analysis of Substituents:
- Phenol (C₆H₅OH): The reference compound with no additional substituent influence.
- p-Methylphenol (p-Cresol): The methyl group is an electron-donating group, which decreases the acidity of phenol by destabilizing the phenoxide ion.
- m-Nitrophenol: The nitro group is a strong electron-withdrawing group. Its meta-position moderately stabilizes the phenoxide ion, increasing acidity compared to phenol.
- p-Nitrophenol: The nitro group at the para position strongly withdraws electrons, providing more stabilization to the phenoxide ion compared to when the nitro group is at the meta position, thus making it more acidic than m-Nitrophenol.
Order of Acidic Strength: Based on the above analysis, the increasing order of acidic strength is:
- p-Methylphenol: Least acidic due to the electron-donating effect of the methyl group.
- Phenol: Moderate acidity as the reference compound.
- m-Nitrophenol: More acidic than phenol due to electron withdrawal by the nitro group.
- p-Nitrophenol: Most acidic due to the strong electron-withdrawing effect of the nitro group at the para position.
Conclusion: Therefore, the correct order of increasing acidic strength is: p\text{-}Methylphenol \lt Phenol \lt m\text{-}Nitrophenol \lt p\text{-}Nitrophenol.

Phenol, p-Methylphenol, m-Nitrophenol and p-Nitrophenol follows order of increasing acidic strength

The Correct Option is B

Solution and Explanation

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