Alkyl hydroperoxides about

Much of what is understood today about the influence of solvent on rates of oxidation reactions with hydrogen peroxide, alkyl hydroperoxides and peroxyacids can be attributed to the seminal studies by Edwards and his collaborators over thirty years ago " . They provided convincing experimental data that showed that a hydroxylic solvent (e.g. ROH) can participate in a cyclic transition state where a proton relay can in principle afford a neutral leaving group attending heterolytic 0-0 bond cleavage (equation 13). 

Disproportionation reaction 7 might be expected to be thermoneutral in the gas phase and perhaps less so in the liquid phase where there is the possibility of hydrogen-bonding. Only for gas phase dimethyl peroxide is the prediction true, where the reaction enthalpy is —0.2 kJmoD. The liquid phase enthalpy of reaction is the incredible —61.5 kJmoD. Of course, we have expressed some doubt about the accuracy of the enthalpy of formation of methyl hydroperoxide. For teri-butyl cumyl peroxide, the prediction for thermoneutrality is in error by about 6 kJmor in the gas phase and by ca 9 kJmoD for the liquid. The enthalpy of reaction deviation from prediction increases slightly for tert-butyl peroxide — 14kJmol for the gas phase, which is virtually the same result as in the liquid phase, — 19kJmol . The reaction enthalpy is calculated to be far from neutrality for 2-fert-butylperoxy-2-methylhex-5-en-3-yne. The enthalpies of reaction are —86.1 kJmoD (g) and —91.5 kJmol (Iq). This same species showed discrepant behavior for reaction 6. Nevertheless, still assuming thermoneutrality for conversion of diethyl peroxide to ethyl hydroperoxide in reaction 7, the derived enthalpies of formation for ethyl hydroperoxide are —206 kJmoD (Iq) and —164 kJmoD (g). The liquid phase estimated value for ethyl hydroperoxide is much more reasonable than the experimentally determined value and is consistent with the other n-alkyl hydroperoxide values, either derived or accurately determined experimentally. 

The major product of this chain is the alkyl hydroperoxide. The secondary products which are observed are the results of the reactions of alkyl radicals in the system with the hydroperoxide or of the secondary spontaneous breakdown of the hydroperoxide if the temperature is sufficiently high. This chain mechanism predominates in the temperature regime from about 30° to about 250°C., for the gas phase or in relatively inert solvents. 

Alkyl hydroperoxides which may also be formed if oxygen is present during processing have an absorption which extends to about 320 nm idiich may lead to the formation of free radicals thus -... 

Oxygen transfer from percarboxylic acids and alkyl hydroperoxides to Mn(TPP)Cl and its axially ligated derivatives (with e.g. ImH) has been studied kinetically [35]. A minimally lO -fold increase in the rate constant is brought about by axial ligand binding. 

The relative rates of [Mo(CO)6]-catalyzed epoxidation of olefins by erf-butyl hydroperoxide in benzene were found to be in the order allyl chloride (0.1) 1-octene (1.0) < styrene (1.3) < 2-methyl-l-heptene (9) < cyclohexene (13) < cis-2-octene (14), norbornene (14) < 2-methyl-2-heptene (75). Thus, electron donation in the form of alkyl groups about the double bond accelerates the reaction rate whereas electron withdrawal tends to retard it [379]. 

Alkyl hydroperoxides show the maximum of the first absorption band in the 2000A region, but the tail of the band extends to about 3200 A. Thsefore, they can absorb a part of the sunlight that reaches the earth 3000 A, see Section I). 

Use of tert-butyl hydroperoxide instead of H2O2 produced a slower reaction (although lucigenin disappeared faster). With H2O2, 0cl is comparable to that of luminol (1.25 x 10" ) but it falls to about 100 fold less with the alkyl hydroperoxide as oxidant. 

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