Propyl radicals, decomposition

In the above analysis of the iso-propyl radical decomposition the micro-canonical rate coefficients were obtained from an experimentally... 

CA, not found 7) J. Smid M. Szwarc, Kinetics of Decomposition of Iso-Butyryl Peroxide and Reactions of Iso-Propyl Radicals , Syracuse Univ, NY, contract DA-30-115-ORD-678 (1958) 8) H.T. Lee et al, Evaluation of... 

In the area of reaction energetics. Baker, Muir, and Andzehn have compared six levels of theory for the enthalpies of forward activation and reaction for 12 organic reactions the unimolecular rearrangements vinyl alcohol -> acetaldehyde, cyclobutene -> s-trans butadiene, s-cis butadiene s-trans butadiene, and cyclopropyl radical allyl radical the unimolecular decompositions tetrazine -> 2HCN -F N2 and trifluoromethanol -> carbonyl difluoride -F HF the bimolecular condensation reactions butadiene -F ethylene -> cyclohexene (the Diels-Alder reaction), methyl radical -F ethylene -> propyl radical, and methyl radical -F formaldehyde -> ethoxyl radical and the bimolecular exchange reactions FO -F H2 FOH -F H, HO -F H2 H2O -F H, and H -F acetylene H2 -F HC2. Their results are summarized in Table 8.3 (Reaction Set 1). One feature noted by these authors is... 

In 1943 Rabinoviteh et al. (83) recognized that at low pressures hot propyl radicals readily undergo decomposition into ethylene and methyl radicals... 

Falconer et al. studied the reactions of H atoms with C3H6 and C3D6 as a function of hydrogen pressure and determined the rates of decomposition (relative to stabilization) of the hot radicals. In the case of n-propyl radicals these rates (fc ) were compared with the calculated theoretical values. The data are summarized in Table VI, where... 

Rate Constants of Decomposition of Hot ra-Propyl Radicals and the Isotope Effects... 

Falconer and Cvetanovic (40) attempted to obtain a more quantitative value for the fraction of nonterminal addition in the case of propylene. They produced hydrogen atoms by mercury photosensitized decomposition of H2, using at least 100 times as much H2 as C3H6 and total pressures of 40 and of 250 mm. Under these conditions the reactions of importance were the combination and disproportionation of the iso- and n-propyl radicals and their cross reactions, the combination of the two radicals with H atoms (assumed to be equally probable), and a very small amount of decomposition of hot n-propyl radicals. Disproportionation to combination ratios were taken as 1.64 for two iso-propyl, 1.14 for two w-propyl, and hence 1.39 was taken as the mean of the two values for one iso- and one n-propyl radical. Using these values and the analysis of the products, the nonterminal addition of H atoms to C3H6 and C3D6 was found to amount to 6 1%. 

Fig. 22. The yield of w-propyl radicals from the mercury-photosensitized decomposition of various propanes as a function of nitric oxide concentration. O—CjH8 ...

Fig. 23. Yield of n-propyl radicals as a function of added 1-butene in the mercury-photosensitized decomposition of propane. —C3D8 O—C3Ha (2 mole-% NO).

It is characteristic that the new entrant methyl group assumes the ortho position to the nitro group and thus a substitution occurs which is similar to nucleophilic attack. Recently it has been found by Jackson and Waters [72] that higher nitrated benzene derivatives such as m- dinitrobenzene, or 1,3,5-trinitrobenzene, become homolytic hydrogen acceptors at temperatures of 80-100°C especially in the presence of the 2-cyano-2-propyl radical, which is formed by thermal decomposition of a,a -azo-bis-isobutyronitrile... 

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... 

Refers to the average energy of the formed n-propyl radicals above 0 (31>0 kcal.) for decomposition to CHa and C3H4. 

Ethylene arises from the ethylidene radical. The decomposition of jec-propyl radical to give a hydrogen atom and propene is taken to be the major source of hydrogen atoms this process is not distinguishable from decomposition of i-butane to a hydrogen atom and a butyl radical followed by decomposition of the latter to a methyl radical and propene. 

At higher temperatures there is decomposition of the propyl radicals, viz. 

Aryl azides undergo induced decomposition when heated at 50-80° in -propyl alcohol in the presence of diethyl peroxydicarbonate (243) For example, 2,4,6-tribromoazidobenzene (242) and 243 (ca. 1 1 mole ratio) in t-propyl alcohol gave a 35% yield of 2,4,6-tribromoaniline 244). It was felt that the radical responsible for the induced decomposition was the 2-hydroxy-i-propyl radical. 

Butyl radicals decompose quickly to form ethylene and propylene. At high temperatures, alkyl radical decomposition reactions constitute an important reaction class and the prevailing fate of alkyl radicals. Take 1-propyl and 1-butyl radicals, for example. These primary alkyl radicals give rise to the following / -decomposition reactions ... 

Similarly, propene can form by decomposition of primary propyl radicals and secondary free radicals. Propane can form by propyl radicals abstracting hydrogen from another source. 

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