On the Ag(1 1 1) surface pre-adsorbed with Cl, TDS and HREELS studies find that vinyl chloride physisorbs molecularly with a binding energy 8 kJ/mol stronger and an adsorption geometry more parallel to the surface in comparison with adsorption on clean Ag(1 1 1). The vinyl chloride in close proximity to the surface Cl has stronger binding energy than the ones further removed from Cl. The binding energy change due to surface Cl can be modeled with charge-dipole interaction between the negatively charged Cl and the large molecular dipole of vinyl chloride.