ADDITION OF SULPHENYL CHLORIDES TO ACETYLENES .8. EFFECT OF ACIDS ON ORIENTATION

The orientation of the addition of benzenesulphenyl chlorides to phenylacetylene in ethyl acetate is largely shifted from anti-Markownikoff to Markownikoff by strong acids like trifluoroacetic and hydrochloric. No effect was observed on the addition to but-1 -yne. The results fit the scheme proposed to explain the effect of solvent on the orientation, and confirm that production of the Markownikoff orientation is related to the possibility of forming a highly polar structure from an initial adduct between the sulphenyl chloride and the aceylene derivative, which would otherwise yield the anti-Markownikoff adduct by internal collapse. A further proof of the trans-stereochemistry of the additions is given.