We present an ab initio study of the interaction of the stratospherically significant compounds HOCl, HCl, H2O, and Cl-2 with four water molecules representing an adsorption site on the surface of hexagonal ice. Using the 6-311++G(d,p) basis set and geometries optimized at the MP2 level of theory, the interaction energies of HOCl, HCl, H2O, and Cl-2 with the water tetramer were found to be -37, -26, -17, and -11 kJ/mol, respectively. Results indicate that when a small foreign molecule interacts with a water adsorption site in these systems, both adsorbed molecule and adsorption site maintain their original geometric and electronic structure. Optimized geometries of the test molecules at the prototypical ice adsorption site are reported.