The increasing order of pKa for the following phenols is
(A) 2,4-Dinitrophenol
(B) 4-Nitrophenol
(C) 2,4,5-Trimethylphenol
(D) Phenol
(E) 3-Chlorophenol
Choose the correct answer from the option given below :
For analyzing pKa trends:
• Electron-withdrawing groups increase acidity (lower pKa).
• Electron-donating groups decrease acidity (higher pKa).
• Consider the position and number of substituents for their effect on the phenoxide ion.
1. Understanding \(pK_a\):
Lower \(pK_a\) values indicate stronger acids.
Electron-withdrawing groups (e.g., \(-\text{NO}_2\), \(-\text{Cl}\)) stabilize the phenoxide ion, increasing acidity (lower \(pK_a\)).
Electron-donating groups (e.g., \(-\text{CH}_3\)) destabilize the phenoxide ion, decreasing acidity (higher \(pK_a\)).
2. Analysis of Substituents:
2,4-Dinitrophenol: Two \(-\text{NO}_2\) groups strongly withdraw electrons, making it the most acidic (lowest \(pK_a\)).
4-Nitrophenol: One \(-\text{NO}_2\) group withdraws electrons, making it less acidic than 2,4-Dinitrophenol.
3-Chlorophenol: \(-\text{Cl}\) is a moderate electron-withdrawing group, making it less acidic than \(-\text{NO}_2\) compounds but more acidic than phenol.
Phenol: The parent compound without additional substituents is less acidic than substituted derivatives with electron withdrawing groups.
2,4,5-Trimethylphenol: Three \(-\text{CH}_3\) groups are electron-donating, making it the least acidic (highest \(pK_a\)).
Final Order:
\[2,4\text{-Dinitrophenol} < 4\text{-Nitrophenol} < 3\text{-Chlorophenol} < \text{Phenol} < 2,4,5\text{-Trimethylphenol}.\]
Given below are two statements:
Statement I: Dimethyl ether is completely soluble in water. However, diethyl ether is soluble in water to a very small extent.
Statement II: Sodium metal can be used to dry diethyl ether and not ethyl alcohol.
In the light of the given statements, choose the correct answer from the options given below:
Compounds A and B, having the same molecular formula \( C_4H_8O \), react separately with \( CH_3MgBr \), followed by reaction with dil. HCl to form compounds X and Y respectively. Compound Y undergoes acidic dehydration in the presence of Conc. \( H_2SO_4 \) much more readily than X. Compound Y also reacts with Lucas reagent, much more readily than X, with the appearance of turbidity. Identify X and Y.
Match List-I with List-II: List-I