Chlorine of vinyl chloride (CH2= CHCl ) is non-reactive (less reactive) towards nucleophile in nucleophilic substitution reaction because it shows resonance due to +M effect of −Cl atom. 
In structure II, Cl-atom have positive charge and partial double bond character with C of vinyl group, so it is more tightly attracted towards the nucleus and it does not get replaced by nucleophile in SN reaction. Related Theory sp3-hybridized electrophile must have a leaving group (X) in order for the reaction to take place.