Peroxides structure

Since the earlier reviewers, and Mallory and Wood, and, for the earlier literature, Hammick el al. have summarized the history of the structure problem fairly fully, and since it cannot in any case be treated properly in isolation from that of the monocyclic furoxans, we shall present only a brief outline here. The earliest formulas to be suggested (3 and 4), in connection with 1,2-naphthofuroxan, discovered by Koreff and von Ilinski in 1886, were open to the objections that the first is a peroxide structure, whereas the benzofuroxans... 

Nair, V. and Turner, G.A. (1984). The thiobarbituric acid test for lipid peroxidation structure of the adduct with malondi-aldehyde. Lipids 19, 804—805. 

In conclusion, structures containing polyiodide anions, with cationic aromatic ligands as counter parts of formulae [(L)(HL+)] (I ) are known to be synthesized by the treatment of the appropriate amide with HI [26-28], In contrast, the complexes with PYOH, in the present case, were formed by the direct reaction of 2-hydroxypyridine with di-iodine in a molar ratio of 2 1 and 1 2. This is a redox reaction, where 2-hydroxy-pyridine firstly is oxidized to pyridinone-2 radical cation. In the case of 2-hydroxy-pyridine however, peroxide structures are not formed like disulphides in the case of PYSH. Polyiodide anions are simultaneously produced in this case This should be a consequence of redox differences between -SH and OH groups and may be proven a useful pathway for the synthesis of polyiodide materials. 

Reactions with ketones yield ketone peroxides. For example, with methyl ethyl ketone, the product is methyl ethyl ketone peroxide, which prohahly is a mixture of monomeric and polymeric products of peroxidic structure. 

NMR spectroscopy, 709 radical polymerization, 707 Poly(methyl methacrylate peroxide), structure, 714-15... 

Further experiments (159), including gas titrations, reactivity studies, and spectroscopic evidence, led to the formulation of the intermediate, earlier postulated (158) to be an oxygenated cobaltocene adduct, as the organic peroxide structure 63, in which the dioxygen bridge once again links the cyclopentadiene ligands in an exo fashion. This complex... 

There is, however, one important objection against the attractive theory of Kilty et al. Their infrared work was carried out at a relatively low temperature. It is very likely that the peroxidic structure is not sufficiently stable at the usual reaction temperatures (200—300°C). 

However there exists no evidence for this. Moreover, investigation of the absorption spectra of nitric acid, nitrous acid and aliphatic nitro compounds indicates that the peroxide structure hypothesis is incorrect, because nitric acid esters behave as compounds having the normal ester structure (II) (Crigee and Schnorrenberg [la], Matsushima [lb]) ... 

Organic peroxides can be classified according to peroxide structure. There are seven principal classes hydroperoxides dialkyl peroxides a-oxygen substituted alkyl hydroperoxides and dialkyl peroxides primary and secondary ozonides peroxyacids diacyl peroxides (acyl and organosul-fonyl peroxides) and alkyl peroxyesters (peroxyearboxylales. peroxysul-fonates, and peroxyphosphates). 

The susceptibility of dialkyl peroxides to acids and bases depends on peroxide structure and the type and strength of the acid or base. In acidic environments, unsyinmetrical acyclic alkyl aralkyl peroxides undergo carbon-oxygen fission, forming acyclic alkyl hydroperoxides and aralkyl carbonium ions. The latter react with nucleophiles, X. ... 

Starting with ketones and hydrogen peroxide in the presence of a catalytic amount of acid, mixtures of up to eight components have been identified, i.e.. (1, X = OH. R3 = H), (1, X = OOH, R3 = H), (2, X = Y = OH). (2, X = Y = OOH), (2, Y = OH, Y = OOH), (3). (4), and (5). The ketone structure and reaction conditions, i.e., acid strength, reactant molar ratios, temperature, and time, determine which compounds form and predominate. Mixtures of several peroxide structures usually are present. Individual peroxides have been isolated from several ketones under different conditions (Table 5). The pure peroxides should be handled with extreme caution since most, especially those derived from the low moleculai weight ketones, ate shock- and friction-sensitive and can explode violently. Methyl ethyl ketone peroxide (MEKP) mixtures are produced commercially only as solutions containing <40 wt% MEKPs in solvents, commonly dialkyl phthalates. 

Chemical Properties. Diacyl peroxides (16) decompose when heated or photolyzed (<300 mm). Although photolytic decompositions generally produce free radicals, thermal decompositions can produce nonradical and radical intermediates, depending on diacyl peroxide structure. Symmetrical aliphatic diacyl peroxides of certain structures, i.e, diacyl peroxides (16, R1 = R2 = alkyl) without a-branches or with a mono-ce-methyl substituent,... 

The calculated temperature profiles of the 180 EIEs and constituent isotopic partition functions are shown in Figure 9.3 for two copper-oxygen complexes.37,38 In these cases, the maximum temperature and the magnitude of the EIE differentiate the end-on and side-on structures. Similar behavior is observed in Tables 9.1 and 9.2, where the 171-superoxide structures are characterized by discernibly smaller 180 EIEs than the p2-peroxide structures. As discussed above, the origin of the differences is... 

O EIEs of 1. 026-1.030 were computed from three experimentally determined frequencies that represent the most isotopically sensitive vibrational modes for side-on peroxide structures. This approach may be superior to the full frequency analysis specifically for the third row metals where the DFT method is less reliable. 

Lanci M. P. Roth J. P. Oxygen isotope effects upon reversible 02-binding reactions characterizing mononuclear superoxide and peroxide structures. J. Am. Chem. Soc. 2006,... 

The assignment of the rf-peroxide structure to these reactive intermediates immediately raised several issues. One could surmise that the behavior would be similar to that of the so-called MoOPH reagents, which are also efficient alkene oxidants. Careful labeling studies have shown that the latter transferred oxygen to substrates from the -peroxide and not from the... 

Structure 3 was assigned to the autoxidation product from 2,4-dimethylpyrrole, whereas a peroxidic structure 4 was ascribed to the product from, e.g., 3-methyl-4-ethylpyrrole, although the presence of active oxygen was not found. 

---