Concept:Aryl halides are extremely unreactive toward standard nucleophilic substitution. However, under extreme industrial conditions (the Dow Process), substitution can be forced.
Formula:$$ \text{C}_6\text{H}_5\text{Cl} + 2\text{NaOH} \xrightarrow{350^\circ\text{C, 150 atm}} \text{C}_6\text{H}_5\text{O}^-\text{Na}^+ + \text{NaCl} + \text{H}_2\text{O} $$
Solution:- Chlorobenzene is treated with aqueous NaOH at very high temperature (350°C) and high pressure (150-300 atm).
- The hydroxide ion displaces the chloride ion. However, because the environment is strongly basic, the initially formed phenol immediately reacts with NaOH to form a salt.
- This intermediate salt is Sodium phenoxide (\( \text{C}_6\text{H}_5\text{O}^-\text{Na}^+ \)).
- (To get pure phenol, a subsequent acidification step with HCl is required).
Why other options are incorrect:- Phenol is the final product only after acid workup, but the direct product of the high-temp NaOH reaction is the phenoxide salt.
- Chromate and sulfate compounds are completely unrelated to these reactants.
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