Formation of phenyl thiocyanate and phenyl isothiocyanate in the reaction of benzenediazonium sulfate, cupric ion and thiocyanate ion (author's transl)

Abstract

In the Sandmeyer reaction of benzenediamnium ion with thiocyanate ion in the presence of cupric ion, the yield of phenyl thiocyanate (I) increased up to 30% with the increase in the molar ratio of thiocyanate ion to cupric ion, in the pH range of 8.0-8.5, whereas that of phenyl iso-thiocyanate (II) increased up to 40% with the decrease of the molar ratio of these reactsnts in the pH range of 1.0-1.5. For the explanation of the difference in the yield of these products, relationship between the reaction of Cu2+ to SCN- and the results of Sandmeyer reaction was examined. The amount of cuprous thiocyanate prpduced and the concentration of cupric thiocyanate in the solution were proportional to the yields of I and II, respectively. Accordingly, cuprous thiocyanate and cupric thiocyanate are considered to be responsible for the formation of I and II, respectively.