Oxidation with ceric sulphate

Explanation A reaction usually takes place by the combination of oxidizing and reducing agents and this may be considered as the basis for the quantitative measurement of one of the reactants. For instance, FeS04 can be determined quantitatively by its reaction with ceric sulphate [Ce(S04)2] as expressed by the following equation ... 

The mechanism of grafting polymer side chains to cellulose by Cerium (IV) ions is best understood by the oxidation of pinacol with ceric sulphate investigated 1959 by Mino, Kaizerman and Rasmussen... 

The number-average molecular weights of starches have been determined by a procedure that involves oxidation of the polysaccharide with potassium hexa-cyanoferrate solution and potentiometric titration of ferrous ions with ceric sulphate. ... 

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

Procedure Weigh accurately about 0.2 g of acetomenaphthone and boil it with 15 ml of glacial acetic acid and 15 ml of dilute hydrochloric acid under a reflux condenser for 15 minutes. Cool the contents carefully and taking adequate precautions to avoid any atmospheric oxidation. Add 0.1 ml of ferroin sulphate solution as indicator and titrate with 0.05 N ammonium ceric sulphate. Repeat the assay without the substance being examined (blank determination) and incorporate the correction, if any. Each ml of 0.05 N ammonium ceric sulphate is equivalent to 0.006457 g of C15H1404. 

Ceric sulphate similarly causes quantitative oxidation. The reaction should take place in the presence of 4N hydrochloric acid, with bivalent manganese present as catalyst and iodine monochloride as indicator. The iodine of the latter is first liberated and then oxidised—8... 

Thioepichlorohydrine reacted with Ce(IV) oxidants in different alcohols under refluxing conditions to produce bis(2-chloro-2 -alkoxy-isopropyl)disulfides in 40-70% yields (Scheme 25). By comparison of the results obtained from the reactions of thiiranes with Ce(IV) oxidants, the order of reactivity of these reagents was found to be as follows ceric ammonium nitrate > ceric triethyl ammonium nitrate > ceric pyridinium nitrate and ceric sulphate. The assumption that the radical cations (59) and (60) are intermediates may account for the mechanism of this reaction <91T149>. 

Ceric sulphate is most often used as oxidant since it oxidizes Sb(III) to Sb(V) quickly in 6 M HCl, even in the cold. Since the excess of Ce(IV) could oxidise RB, it is reduced with hydroxylamine, which does not reduce the Sb(V) under the conditions of the reaction. That Ce(lV) is reduced by the HCl itself is indicated by the bleaching of the yellow solution even before the addition of NH2OH HCl. Hydroxylamine reduces, first of all, the chlorine formed, which, if left in the solution, would oxidise the Rhodamine B added later. As an alternative... 

The synthesis and reactions of naphthoquinones have received attention. The reaction of 2,6-dichloro-benzoquinones with the keten acetal CH2=C(OEt)2 in acetic acid results in high yields of the naphthoquinones (303), while oxidation " of the naphthalenes (304) with ceric ammonium sulphate gives the naphthoquinones (305) by a 1,2-shift (Scheme 39), as demonstrated by deuterium-labelling experiments. 

To approximately 0-2 g acetomenaphthone add 15 ml of glacial acetic acid and 15 ml of dilute hydrochloric acid and boil under reflux condenser for at least fifteen minutes. Cool, protecting against aerial oxidation, and titrate with 0 05N ceric ammonium sulphate using 01 ml of o-phenanthroline-ferrous complex as indicator. Carry out a blank determination using exactly the same amount of indicator. 1 ml 0-05N = 0-006457 g. 

---