Explain why an alkyl halide (or methyl chloride) is hydrolysed more readily than aryl halide (or chlorobenzene).

Due to high electronegativity of halogen atom (say chlorine atom), the —C—X (or Cl—Cl) bond in alkyl halide (or methyl chloride) is slightly polar and carbon atom of—C—X (or —C—Cl) bond acquires a slight positive charge. Thus

The C^δ+ atom is easily attacked by nucleophile (electron-rich species), such as OH^–. Thus hydrolysis takes place easily.

On the other hand, aryl halide (or chlorobenzene) is resonance stabilized, so the C—Cl bond has a partial double character. Consequently, the rupture of this partial double bond becomes rather difficult. Hence, aryl halide (or chlorobenzene) is less reactive than alkyl halide (or chloromethane). Moreover, the C—Cl bond in aryl halide has a sp²hybridized C-atom, while it is sp³ hybridized in alkyl halide (or chloromethane). Since sp³ hybrid C-atom is more electronegative than the sp³ hybrid C-atom, so C–Cl bond in aryl halide (or chlorobenzene) has less tendency to release electrons to Cl-atom. In other words, the C—Cl bond in aryl halide (or chlorobenzene) is less polar than in alkyl halide (or chloromethane). This makes nucleophilic substitution (say by OH^– group) more difficult. Hence, alkyl halide (or methyl chloride) is hydrolysed more readily than aryl halide (or chlorobenzene).