Isopropyl radical decomposition

When )3-scission can occur in the radical, further reactions compete with acid amide formation. Thus oxaziridine (112) with iron(II) ion and acid yields stabilization products of the isopropyl radical. If a-hydrogen is present in the Af-alkyl group, radical attack on this position in (113) occurs additionally according to the pattern of liquid phase decomposition. 

With ketones which can eject radicals more stable than methyl, fragmentation competes more successfully with all physical processes than in acetone, and unsymmetrical ketones preferentially eject the more stable alkyl radical.309 Thus both methyl ethyl ketone310 and methyl isopropyl ketone311 yield chiefly acetyl and ethyl or isopropyl radicals. Half of the diethyl ketone molecules excited by 3130-A irradiation at 25° decompose from the excited singlet state before they can undergo intersystem crossing, and another 40% fragment from the triplet state.312 Both fluorescence and phosphorescence are extremely weak. The more rapid decomposition in both excited states relative to that observed in acetone almost eliminates competition from physical-decay processes. 

Chilton and Gowenlock85,87 pyrolyzed (z -C3H7)2Hg with NO and N2 as a carrier gas in a flow system at 230-280°C. They found (CH3)2 CHN=0 and (CH3)2C=NOH as products,85 the latter arising from the isomerization of the former. Woodall and Gunning454 studied the sensitized [Hg 6(3.Pi) plus NO Ilj)] decomposition of propane and its deuterated analogs at room temperature. Both n-propyl and isopropyl radicals were produced and added to NO. The product isomers, i.e., the respective oximes, were the principal products. An unusual feature of this study was that the oximes were formed readily at room temperature. The authors suggested that the reactant radicals might have been hot, and this coupled with the heat of addition could have facilitated the isomerization. 

This should be compared to the slowest possible chain path for the isopropyl alcohol decomposition, which (like /-butyl alcohol) is one propagated by allyl type radicals. A calculation, similar to that for /-butyl alcohol (shown above), where the major chain process is... 

However, this is probably an oversimplification, as the disproportionation reaction is surface-catalyzed and the two reactions must have different energies of activation. This behavior of dimethylamino radicals is in marked contrast to the iso-electronic isopropyl radicals, the disproportionation-combination ratio of which is unaltered by temperature and siuface (2, 30). The surface-promoted radical decomposition is also in marked contrast to the absence of such effects in the isopropyl radical reactions (2) and must be attributed to the presence of the nitrogen atom. Amino radicals also undergo surface reactions (28). The occurrence of TMA suggests the participation of methyl radicals in the reactions, and a possible route is provided by Reactions 28 and 34. 

Figure 2.1 shows that, once formed, the hydrocarbon radical can undergo a number of reactions, one of which is decomposition e.g., the decomposition of the isopropyl radical into H atoms, which can propagate the chain reaction, and propene. 

Effects other than those of purely viscometric origin were seen to be significant in a schematic study by McHugh and co-workers of the free radical decomposition of cumene hydroperoxide [48], and subsequent oxidation of cumene (isopropyl benzene) [49, 50] in a range of supercritical and liquid solvents. The effective non-catalysed rate coefficients for cumene hydroperoxide decomposition in non-polarisable supercritical fluids (krypton, xenon) were greater than that for non-polar liquid cyclohexane, as expected a priori on the basis of viscosities. Yet, liquid 1-octene and 1-hexanol gave similar... 

Pyrolysis of the phosphorodichloridothioate (59) at 550 °C gives mainly dibenzothiophen and a smaller amount of the cyclic phosphonochlorido-thioate (60). Thermal decomposition of di-t-butyl peroxide in triethyl phosphate gives rise to diethyl methyl phosphate in a reaction which may be interpreted as resulting from attack of methyl radical on the phosphoryl oxygen. An extension of this mechanism accounts for the formation of (61) from tri-isopropyl phosphate under the same conditions. 

We examined the thermal decomposition of a number of nitramines in dilute solution and in the melt phase. The nitramines included acyclic dialkyl mononitramines, where the dialkyls were methyl, ethyl, propyl and isopropyl cyclic mononitramines (N-nitro-pipeiidine and N-nitropyrrolidine) and cycle multifunctional nitramines (N-dinitropiperazhe l,3-dinitro-l,3-diazacyclo-pentane l,3-dinitro-l,3-diazacycbhexane RDX and HMX). For all nitramines, the predominant condensed-phase product was the nitrosamine though the amount formed depending on the nitramine and the phase of the thermolysis. The common trigger in the decompositions was N-N02 ho mo lysis, but the fate of the resultant amine radical depended on the phase. In solution the radical was stabilized sufficiently so that it resisted further decomposition and, instead, reacted with NO to form nitrosamine. In vapor or condensed phase, the amine radical underwent further reaction therefore,... 

Allylic derivatives R3MCH2CH=CH2 (M = Ge, Sn, Pb) react with a number of element-centered radicals YPh (Y = S, Se, Te) formed in the decomposition of the corresponding dichalcogen compounds PhYYPh53. R3MCH2CH=CH2 also reacts with the isopropyl free radical generated by the decomposition of i -PrHgCl. It has been found... 

Propyl Radicals n-CsHi —> CHt + CJli. The models for n-propyl decomposition are given in Appendix III. eA was set at 3.1 as opposed to 1.6 kcal. for isopropyl formation. Values of kt are presented in Figure 12. Table XX summarizes some calculated values for various activation systems. H atom rupture is seen to be orders of magnitude slower than C—C bond rupture. Again, comparison may best be made with the results from chemical activation studies at 25°C. The observed values were ka0 = 8 X I07 and /bO0O = 18 X I07 sec.-1. The data fluctuated... 

It is clear that if we are to use photolysis to study the reaction of radicals with oxygen it would be preferable to use conditions under which decomposition of the parent molecule occurs primarily from the singlet excited state. However, there is good evidence that methyl isopropyl ketone129 and 2-pentanone141 can be deactivated from the singlet excited state by sufficient pressures of biacetyl. 

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