Some copper (I) and (II) compounds have been found to act as efficient reagents for the nucleophilic displacement of 1-haloalkynes. Copper (I) iodide smoothly transforms 1- bromoalkynes (2) into 1-iodoalkynes (1) which, on further treatment with copper (II) bis (arenesulfinate), are readily converted to the corresponding alkynyl aryl sulfones (4). The kinetic data of the halogen exchange between (4-chlorophenyl) ethynyl bromide (2d) and ...