Why is 4-chlorophenol soluble in 2.5M NaOH solution, but not in water?
A. Phenol is a weak acid so it can be deprotonated under basic conditions.
B. Aqueous acid destroys 4-chlorophenol.
C. 4-chlorophenol is only soluble in water at low temperature.
D. A and C
E. None of the above.
To understand why 4-chlorophenol is soluble in a 2.5M NaOH solution but not in water, we need to consider the properties and behavior of 4-chlorophenol and the role of NaOH.
4-chlorophenol, as the name suggests, is a phenol compound with a chlorine atom attached to the phenol ring. Phenol itself is a weak acid, which means it can donate a proton (H+) in a chemical reaction. The solubility of phenols and their derivatives in water depends on their ability to form hydrogen bonds with water molecules.
In the case of 4-chlorophenol, the presence of the chlorine atom enhances its acidity compared to regular phenol. When 4-chlorophenol is dissolved in water alone, its solubility is limited because it can only form weak hydrogen bonds with water molecules.
However, when 4-chlorophenol is added to a 2.5M NaOH solution, a basic environment is created. NaOH is a strong base, capable of dissociating into sodium ions (Na+) and hydroxide ions (OH-). The hydroxide ions, being strongly basic, can deprotonate the 4-chlorophenol molecule by accepting the proton from the phenol group.
The deprotonation reaction of 4-chlorophenol with hydroxide ions forms the corresponding phenoxide ion and water:
4-chlorophenol + NaOH -> 4-chlorophenoxide ion + H2O
The resulting 4-chlorophenoxide ion is highly soluble in water due to its negative charge and the ability to form stronger hydrogen bonds with water molecules compared to the neutral 4-chlorophenol.
In summary, 4-chlorophenol is soluble in a 2.5M NaOH solution because it can be deprotonated by hydroxide ions, forming a soluble phenoxide ion. However, it is not soluble in water alone because it can only establish weak hydrogen bonds with water molecules. Therefore, the correct answer is option D: A and C.