Oxidative free-radical additions and

Snider BB (2009) Mechanisms of Mn(OAc)3-based oxidative free-radical additions and cyclizations. Tetrahedron 65 10738-10744... 

Mn(OAc)3-Based Oxidative Free-Radical Additions and Cyclizations... 

Mn(OAc)3-based oxidative free-radical additions and cyclizations proceed by at least two different mechanisms. The rate-determining step is the slow reaction of acetic acid or 3-keto ester with Mn(OAc)3 to give Mn(III) enolates. The rate of proton loss is proportional to the acidity of the... 

Most kinetic treatments of the photo-oxidation of solid polymers and their stabilization are based on the tacit assumption that the system behaves in the same way as a fluid liquid. Inherent in this approach is the assumption of a completely random distribution of all species such as free radicals, additives and oxidation products. In all cases this assumption may be erroneous and has important consequences which can explain inhibition by the relatively slow radical scavenging processes (reactions 7 and 9) discussed in the previous section. 

Warsinsky R, Steckhan E (1995) Oxidative free radical additions of a-nitro amides to alkenes and alkynes mediated by electrochemically regenerable manganew (HI) acetate. In Torii S (ed) Novel trends in electroorganic synthesis, Kodansha, Tokyo, pg 135 J. Chem. Soc. Perkin Trans 1 (1994) 1994 2027... 

Oxidative Free-Radical Cyclizations and Additions with Mono and / -Dicarbonyl Compounds... 

The mercaptan group is one of the most reactive functional groups in all organic chemistry, and it readily undergoes oxidation, nucleophilic displacement, nucleophilic addition, and free-radical addition and displacement reactions. This section discusses some of the chemical literature pertaining to these types of reaction in reduced keratin fibers and illustrates the potential reactivity of the mercaptan group in hair. 

Non-active anodes do not bind the oxygen atom of A OH covalently. The sorbed hydroxyl radicals (physisorbed active oxygen) have high and nonspecific reactivity towards organic substrates through free radical addition and/or hydrogen abstraction reactions, which can lead to full or partial mineralization of the substrate. This mode of oxidation is variously known as electrochemical combustion, electrochemical incineration, or an electrochemical advanced oxidation process (EAOP), the latter by analogy with conventional AOPs that also involve hydroxyl radicals ... 

Interest in synthetic naphthenic acid has grown as the supply of natural product has fluctuated. Oxidation of naphthene-based hydrocarbons has been studied extensively (35—37), but no commercially viable processes are known. Extensive purification schemes must be employed to maximize naphthene content in the feedstock and remove hydroxy acids and nonacidic by-products from the oxidation product. Free-radical addition of carboxylic acids to olefins (38,39) and addition of unsaturated fatty acids to cycloparaffins (40) have also been studied but have not been commercialized. 

In this chapter, we discuss free-radical substitution reactions. Free-radical additions to unsaturated compounds and rearrangements are discussed in Chapters 15 and 18, respectively. In addition, many of the oxidation-reduction reactions considered in Chapter 19 involve free-radical mechanisms. Several important types of free-radical reactions do not usually lead to reasonable yields of pure products and are not generally treated in this book. Among these are polymerizations and high-temperature pyrolyses. 

Mechanisms of aldehyde oxidation are not firmly established, but there seem to be at least two main types—a free-radical mechanism and an ionic one. In the free-radical process, the aldehydic hydrogen is abstracted to leave an acyl radical, which obtains OH from the oxidizing agent. In the ionic process, the first step is addition of a species OZ to the carbonyl bond to give 16 in alkaline solution and 17 in acid or neutral solution. The aldehydic hydrogen of 16 or 17 is then lost as a proton to a base, while Z leaves with its electron pair. 

CH Nj reactions, 382 COClj reactions, 383 free radical addition of hexafluoroacetone, 257 identification of oxidation products CHjNj to measure peracids as peresters, 385 extinction coefficients, 388-389/ iodometry to measure -OOH, 385 NO to measure alcohols and hydroperoxides, 386 residual, simplified carbonyl envelope which results from SF exposure, 386... 

Compounds of transition metals (Mn, Cu, Fe, Co, Ce) are well known as catalysts for the oxidation of hydrocarbons and aldehydes (see Chapter 10). They accelerate oxidation by destroying hydroperoxides and initiating the formation of free radicals. Salts and complexes containing transition metals in a lower-valence state react rapidly with peroxyl radicals and so when these compounds are added to a hydrocarbon prior to its oxidation an induction period arises [48]. Chain termination occurs stoichiometrically (f 1) and stops when the metal passes to a higher-valence state due to oxidation. On the addition of an initiator or hydroperoxide, the induction period disappears. 

The detailed mechanism for these Co AlPO-18- and Mn ALPO-18-cata-lyzed oxidations are unknown, but as previously pointed out vide supra) and by analogy to other metal-mediated oxidations a free-radical chain auto-oxidation (a type IIaRH reaction) is anticipated [63], This speculation is supported by several experimental observations that include (1) an induction period for product formation in the oxidation of n-hexane in CoAlPO-36, (2) the reduction of the induction period by the addition of free-radical initiators, (3) the ability to inhibit the reaction with addition of free-radical scavengers, and (4) the direct observation of cyclohexyl hydroperoxide in the oxidation of cyclohexane [62],... 

Interest in synthetic naphthenic acid has grown as the supply of product has fluctuated, Oxidation of naphthene-based hydrocarbons, free-radical addition of carboxylic acids to olefins, and addition of unsatnrated fatty acids to cycloparaflins have been studied but not commercialized. 

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