Tetroxide decomposition, activation

The Rate Constants and Activation Energies of Tetroxides Decomposition ROOOOR R03 + RO ... 

Adamic, Howard and Ingold (2 ) have used the thermodynamic parameters for the t-Bu02 -t-BuOitBu-t equilibrium and activation parameters for irreversible radical decay to calculate activation parameters for irreversible tetroxide decomposition. Decay... 

Nangia and Benson [185] noted that such one decomposition act should have high activation energy (more than 18 kJ mol ) and does not occur rapidly. The preexponential factor A of concerted decomposition should be less than value 1013 s 1 [186], Consequently such one-step decay of tetroxide should occur slowly. 

The reaction between two peroxyl radicals gives a labile compound, which Stockhausen and coworkers [38,39] regard as a hydrotetroxide. The formed tetroxides are very unstable and their decomposition results in the formation of active free radicals. 

From my estimates on the thermodynamic properties of peroxy and polyoxide molecules and radicals, we can estimate that the bond dissociation energy of the tetroxide is about 5 kcal. Thus, at room temperature, or even at dry ice temperature, the tetroxide is extremely unstable and should redissociate into the more stable (from a thermodynamic point of view) peroxy radicals. The competing step would be a concerted decomposition into an RO and an R03 (Step 14) radical, which would be uphill by 20 kcal., or else a concerted decomposition into 2 RO radicals and 02 (Step 14 ). The latter is almost thermoneutral. If we take the current data at face value, it provides, from the reported activation energy at least, strong evidence that the propagating interaction of two alkylperoxy radicals proceeds in a concerted fashion. 

HAZARD RISK Explosive when mixed with nitrogen tetroxide, dimethyl amino propy amine or liquid ammonia vigorous reaction when mixed with propylene dichloride, orthodichlorobenzene and aluminum incompatible with strong oxidizers, strong caustics and active metah such as aluminum, powdered magnesium, sodium or potassium decomposition emits toxic vapors dangerous fire hazard if exposed to heat, flame or oxidizers NFPA code H 2 F 3 R 0. 

Values of and in conjunction with AS12 and AH 2 have been used to calculate the activation parameters log(Ai 3/s )=1T.1 and El 3=16.5 kcal mol for irreversible decomposition of di-CTjmyl tetroxide (lU). Although there is little difference between the activation parameters for di-c miyl- and di-t-butyl-tetroxides it would appear that the former is somewhat less stable towards irreversible decomposition. 

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