Chromium(VI), in the form of chromic acid and metal dichromates, is a versatile oxidant with some serious disadvantages. Inorganic chromates and dichromates are generally insoluble in most organic solvents and are soluble in water only, whereas most organic compounds are insoluble in water. Therefore, immiscibility is limiting factor in working with inorganic Chromium(VI) compounds. Further, inorganic Cr(VI) oxidants are drastic and less selective. In view of these difficulties, a number of complex chromium derivatives have been prepared and used in synthetic organic chemistry. In view of these difficulties, a number of complex chromium derivatives have been prepared and used in synthetic organic chemistry. Two such derivatives are butyltriphenylphosphonium dichromate (BTPPD) and benzimidazolium dichromate (BIDC). This book is about kinetics and mechanism aspects of the oxidation with these two oxidants.