Aliphatic Hydroperoxides

Turner JO. The acid-catalyzed decomposition of aliphatic hydroperoxides reactions in the presence of alcohols. Tetrahedron Lett 1971 14 887-890. 

Problem 28.6 Treatment of aliphatic hydroperoxides, RCHaO—OH and R2CHO—OH, with aqueous acid yields aldehydes and ketones as the only organic products. What conclusion do you draw about migratory aptitudes ... 

FLUORINECOMPOUNDS,ORGANIC - FLUORINATED ALIPHATIC COMPOUNDS] (Vol 11) Isopropyl hydroperoxide [3031-75-2]... 

Aromatic aldehydes and cyclic perfluoroketones are oxidized to a-hydroxy hydroperoxides or bis(a-hydroxy) peroxides, aliphatic ketones are converted to esters, and ketenes are converted to a-lactones... 

The a-hydroxy hydroperoxides obtained by the above reacbon (equation 61) can oxidize highly fluonnated aliphatic aldehydes [70] (equation 62)... 

Organic peroxides and hydroperoxides decompose in part by a self-induced radical chain mechanism whereby radicals released in spontaneous decomposition attack other molecules of the peroxide.The attacking radical combines with one part of the peroxide molecule and simultaneously releases another radical. The net result is the wastage of a molecule of peroxide since the number of primary radicals available for initiation is unchanged. The velocity constant ka we require refers to the spontaneous decomposition only and not to the total decomposition rate which includes the contribution of the chain, or induced, decomposition. Induced decomposition usually is indicated by deviation of the decomposition process from first-order kinetics and by a dependence of the rate on the solvent, especially when it consists of a polymerizable monomer. The constant kd may be separately evaluated through kinetic measurements carried out in the presence of inhibitors which destroy the radical chain carriers. The aliphatic azo-bis-nitriles offer a real advantage over benzoyl peroxide in that they are not susceptible to induced decomposition. 

Hydroperoxides are formed in each polymer containing aliphatic hydrocarbon chains on standing by various initiators, including light, heat, etc. This may be well detected by the non-isothermal chemiluminescence method in nitrogen. The analytical possibilities of this approach have not been fully utilized until recently [17],... 

Recently, the oxidation of primary aliphatic amines to the corresponding nitro compounds has also been achieved using the catalyst system based on zirconium tetra tert-butoxide and tert-butyl hydroperoxide in a molecular sieve (50-98% yield) (Eqs. 2.56 and 2.57 and Table... 

Hydroperoxides were proved to be the only primary molecular product of the oxidation of aliphatic and alkylaromatic hydrocarbons [79-84], When the hydrocarbon is oxidized under mild conditions, in which the formed hydroperoxide is a stable product, the amount of produced ROOH was found to be nearly equal to the amount of consumed dioxygen [45,80,82],... 

A very serious problem was to clear up the formation of hydroperoxides as the primary product of the oxidation of a linear aliphatic hydrocarbon. Paraffins can be oxidized by dioxygen at an elevated temperature (more than 400 K). In addition, the formed secondary hydroperoxides are easily decomposed. As a result, the products of hydroperoxide decomposition are formed at low conversion of hydrocarbon. The question of the role of hydroperoxide among the products of hydrocarbon oxidation has been specially studied on the basis of decane oxidation [82]. The kinetics of the formation of hydroperoxide and other products of oxidation in oxidized decane at 413 K was studied. In addition, the kinetics of hydroperoxide decomposition in the oxidized decane was also studied. The comparison of the rates of hydroperoxide decomposition and formation other products (alcohol, ketones, and acids) proved that practically all these products were formed due to hydroperoxide decomposition. Small amounts of alcohols and ketones were found to be formed in parallel with ROOH. Their formation was explained on the basis of the disproportionation of peroxide radicals in parallel with the reaction R02 + RH. 

The enthalpy of the R02 + RH reaction is determined by the strengths of disrupted and newly formed bonds AH= Z>R H—Droo—h- For the values of O—H BDEs in hydroperoxides, see the earlier discussion on page 41. The dissociation energies of the C—H bonds of hydrocarbons depend on their structure and vary in the range 300 - 440 kJ mol-1 (see Chapter 7). The approximate linear dependence (Polany-Semenov relationship) between activation energy E and enthalpy of reaction AH was observed with different E0 values for hydrogen atom abstraction from aliphatic (R1 ), olefinic (R2H), and alkylaromatic (R3H) hydrocarbons [119] ... 

The concurrent slow homolytic reaction gives rise to free radicals [14]. The occurrence of the homolytic reaction can be revealed by the consumption of free radical acceptors [8,15], CL [16], or NMR spectroscopy [17,18]. The introduction of phosphite into the hydroperoxide-containing cumene causes an initiation, pro-oxidative effect related to the formation of free radicals [6]. The yield of radicals from aliphatic phosphites is much lower (0.01-0.02%) than that from aromatic phosphites (up to 5%) [17]. The homolytic reaction of phosphites with hydroperoxide has a higher activation energy than the heterolytic reaction, which results in the predominance of the former reaction at elevated temperatures. 

Bashkirov A process for making aliphatic alcohols by oxidizing paraffins. The reaction is conducted in the presence of boric acid, which scavenges the hydroperoxide intermediates. Borate esters of secondary alcohols are formed as intermediates and then hydrolyzed. Developed in the USSR in the 1950s and now operated there and in Japan. 

Complex (1) is a catalyst for selective oxidation of benzylic, allylic alcohols to aldehydes, and secondary alcohols to ketones using r-butyl hydroperoxide. Primary aliphatic alcohol oxidation failed. The use of cumyl hydroperoxide as radical probe discounted the involvement of i-BuO /t-BuOO. Hammett studies p = -0.47) and kinetic isotope effects kn/ku = 4.8) have been interpreted as suggesting an Ru—OO—Bu-i intermediate oxidant. 

The authors also investigated the mode of activation of these BINOL-derived catalysts. They proposed an oligomeric structure, in which one Ln-BINOL moiety acts as a Brpnsted base, that deprotonates the hydroperoxide and the other moiety acts as Lewis acid, which activates the enone and controls its orientation towards the oxidant . This model explains the observed chiral amplification effect, that is the ee of the epoxide product exceeds the ee of the catalyst. The stereoselective synthesis of cw-epoxyketones from acyclic cw-enones is difficult due to the tendency of the cw-enones to isomerize to the more stable fraw5-derivatives during the oxidation. In 1998, Shibasaki and coworkers reported that the ytterbium-(f )-3-hydroxymethyl-BINOL system also showed catalytic activity for the oxidation of aliphatic (Z)-enones 129 to cw-epoxides 130 with good yields... 

With the formation of free radicals having been initiated, these radicals react with oxygen (Reaction 3) to begin the propagation of the radical chains in forming a peroxy radical. The peroxy radical then attacks the 10-carbon-hydrogen bond to form the hydroperoxide radical (Reaction 4). [The possibility of such an intramolecular attack has been demonstrated in an aliphatic system where two reactive hydrogen atoms are located in the favorable 1,4-positions (9)]. 

It is generally observed that a C—H bond which is antiperiplanar to a lone pair of electrons (65) is weakened and susceptible to removal by electrophilic or free-radical oxidizing agents. This provides an explanation for the ready hydroperoxidation of aliphatic ethers, both cyclic and acyclic, by atmospheric oxygen. These considerations, however, go beyond the special area of six-membered heterocyclic reactivity presently considered. 

Scheme 233 Formation of aliphatic flavour aldehydes and alcohols, a Biotechnological reaction sequence mimicking plant biosynthesis of C6 compounds (green notes ), b HomologoiK reaction sequence in fimgi leading to mushroom-like C8 compounds. The stoichiometric formation of w-oxo-carboxylic acids during hydroperoxide lyase cleavage is not depicted...

All these reactions were run essentially as described for the formation of 1,3-diphenylurea for the aromatic amines and 1,3-dibenzylurea for the aliphatic amines. The products were identified by comparison with separately synthesized authentic specimens. b Cumene hydroperoxide. 

Hydroperoxides and peroxides oxidize primary and secondary aliphatic amines to imines. Thus f-butyl hydroperoxide oxidizes 4-methyl-2-pentyl-amine to 2-(4-methylpentylidene)-4-methyl-2-pentylamine in 66% yield [29]. Di-r-butyl peroxide reacts in a similar manner [29]. However, this reaction is... 

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