Melamine reacted with neat sulfuric acid and fuming nitric acid readily to form two new organic solid acids, namely melamine-(H2SO4)3 and melamine-(HNO3)3. Mixture of them acts as a unique powerful system instead of a hazardous H2SO4/HNO3 system for the direct oxidation of thiols. Also, this system can oxidize the sulfides in the presence of a catalytic amount of KBr and few drops of water. This procedure offers advantages such as very low reaction time, simple work-up, excellent yield and matching with some green chemistry protocols.
