Method for making diarylhalonium salts

Claim 1

In a method for making bisulfate salts of the formula, [(R).sub.a (R.sup.1).sub.b I].sup.+ [HSO.sub.4 ].sup.-, where R is a monovalent aromatic organic radical selected from the class consisting of aromatic carbocyclic or heterocyclic having from 6-20 carbon atoms, R 1 is a divalent aromatic organic radical, a is a whole number equal to 0 or 2, b is a whole number equal to 0 or 1, and the sum of a+b is equal to 1 or 2, or the valence of I, which comprises (A) effecting a coupling reaction between a C.sub.(6-30) aromatic compound and potassium iodate in the presence of a mixture consisting essentially of acetic acid, acetic anhydride and sulfuric acid, and (B) recovering the resulting diaryliodonium bisulfate salt from the mixture of (A), wherein the improvement comprises substituting methylene chloride for the acetic acid to produce an acetic acid-free mixture in the coupling reaction, which is conducted at a temperature in the range of from -25° C. to +25° C., whereby improved yields of diaryliodonium bisulfate salt and shorter reaction times are achieved.