Cerium hydrolytic reactions

A number of studies of the hydrolytic reactions of cerium(III) have reported stabihty constants for Ce(OH)3(aq) (Fatin-Rouge and Biinzh, 1999 Bentouhami et al., 2004 Teksoz, Acar and Onak, 2009). None of the constants given are consistent with the stability constant selected in this review for CeOH and, as such, are not retained. This is also the case for the constant derived by Bilal and Koss (1981) for Ce(OH)2 and, as such, this datum is also not retained (this will also be the case for other data reported by Bilal and Koss). 

In a novel attempt to synthesize dihydroindenoindoles (which are very potent antioxidants413,414), reaction of an aryllithium reagent with a 2-bromoindanone has been reasonably successful (equation 54)415. The coupled product is readily converted into the target molecule by the use of hydrolytic conditions and reaction yields are significantly improved by the use of cerium(III) chloride as a catalyst. 

In the oxidation of organic species, terminal oxidation products are CO2, HCOOH (formic acid) and H2O. As Ce(lV) is typically the hmiting reagent, intermediate products are often identified to confirm reaction pathways. Since cerium(IV) is a one-electron oxidant and the organic substrates are two-electron donors, the chemistry of the oxidized substrate involves subsequent reactions of free radical species. The presence of free radicals is verified experimentally by the initiation of polymerization upon addition of methacrylic acid, or other easily polymerized organic species. In some cases the radicals are stable enough to have been studied by ESR (electron spin resonance) methods. There are a few examples of reactions which exhibit an inverse dependence on [Ce(III)], which can be interpreted in terms of hydrolytic dimers or reversible reactions of the type... 

Equilibrium constants of the hydrolysis reaction [eq, (32)] have been reported lor the trivalent lanthanides and tetravalent cerium but not for the divalent lanthanide cations. The latter would be even weaker acids due to a lower charge density than the Ln cations. A variety of mononuclear and polynuclear hydrolytic species have been reported and the values of the hydrolysis equilibrium constants in the literature are listed in tables 12 (mononuclear) and 13 (polynuclear). Baes and Mesmer (1976) have reviewed the hydrolysis reactions of the lanthanides so the scope of this review is limited to the studies which have appeared since the publication of their book. The species are discussed in terms of mononuclear species Ln(OH) , = 1 to 6) and polynuclear species... 

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