Why can't chloroacetic acid be called 1- chloroacetic acid? Our teacher said that it can only be called monochloroacetic acid, and it can't be expressed by numbers.

The number "1" represents which carbon the functional group Cl is attached to, and "one" represents how many Cl's there are. Because the Cl attached to acetic acid can only be attached to the second carbon (generally speaking, the naming order of carbon chains with carboxyl functional groups begins with carboxyl functional groups), the number "1" is wrong, and it is also called 2- chloroacetic acid according to the standard organic naming rules, but the only carbon that can attach Cl to acetic acid is actually that one, so it shows that the position of carbon attachment is actually meaningless. Significantly, a lot of Cl can be attached to a carbon, so we need to get it.