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Explain why CH_(3)Cl undergoes hydrolysis at a faster rate in the presence of Nal. |
Answer» Solution :The hydrolysis of methyl chloride in aquous medium TAKES place at a much slower rate because `H_(2)O` is a weak nucleophile (because it is a neutral nucleophile and the attacking oxygen atom is highly electronegative and less polarisable) and `Cl^(Theta)` is not a very good leaving group (becuase it is not a very weak base and the C-Cl bond is not very weak).  The iodide ion `(I^(Theta))` catalyses the hydrolysis of `CH_(3)Cl`. Due to high polarisability and low solvation energy, `I^(Theta)` is a good nucleophile. Again, for its weak basicity and low bond energy of the C-I bond `I^(Theta)`can ACT as an effective catalyst in substitution reactions. In the presence of NaI, the hydrolysis of `CH_(3)Cl` takes place by the following two steps-  Each of these two reactions [(2) and (3)] takes place at a faster rate than the reaction (1) because `I^(Theta)` is a better nucleophile than `H_(2)O` and it is a better leaving group than `Cl^(Theta)` . As a RESULT, the overall hydrolysis OCCURS at a faster rate in the presence of Nal. it is a case of nucleophilic catalysis. |
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