# What makes a good chlorinating agent?

From what I know, good inorganic chlorinating agents, $$\ce{SOCl2, PCl3, PCl5}$$ are able to substitute a poorer leaving group (like $$\ce{OH-}$$) for chlorine. For example, for substitution of the hydroxyl group to a halide to form a haloalkane, we can't just use hydrogen halides (we can if we first dehydrate it into an alkene, but that is besides the point), but instead use strong chlorinating agents like those mentioned above. I know $$\ce{Cl2, HCl, ClO-, CCl4}$$ etc. are also chlorinating agents, so what makes them "inferior"? Also, why are some other chlorine-containing compounds like $$\ce{ClO3-, CH3COCl, C2H5Cl}$$ not considered good chlorinating agents?

Is it similar to how we gauge the oxidizing strength by seeing how high the oxidation number is (the higher the oxidation state or electronegativity, the more electron-hungry it is, and the more willing it is to accept electrons)? Maybe I'm overthinking this and it's just because the bond enthalpy is lower?

• Consider the properties of the products formed SO2 and POCl3 etc. How strong are the S-O and P-O bonds? How does Le Chatelier's principle drive hte process if one of the products is a gas? – Waylander Oct 12 at 12:47