Question

Vinyl chloride is hydrolysed more slowly than ethyl chloride

Answer 1

In vinyl chloride, the pi electron cloud repels the incoming nucleophile and hinders backside attack, which decreases SN2 reaction. Also vinyl carbocation is unstable, which decreases the possibility of SN1.
In ethyl chloride, however, SN2 can take place as backside attack of nuclophile is much easier.

Answer 2

vinyl chloride is hydrolysed more slowly than ehtyl chloride because the c-cl bond in vinyl chloride has sp2 hybridisation and the c-cl bond in vinyl chloride has more s character from the c atom ,therefore, the bond is stronger and more difficult to break

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