Pentyl radicals

Alkylaminocarbonyl radical, pentyl- (3 isomers CONHCH2CH2CH2CH2CH3 XXVI1-1... 

In the first step (equation 50) pentane is oxidized to a cation radical which on losing a proton becomes a radical. Pentyl radicals can react to form a C p-dimer (equation 51) or disproportionate with pentane and pentene formation (equation 52). Pentene may be alkylated also forming a C.jQ-dimer intermediate (equation 53). The final products of the reaction are formed as a result of C Q-isomerization and decomposition. 

Flowers M C and Rabinovitch B S 1985 Localization of excitation energy in chemically activated systems. 3-ethyl-2-methyl-2-pentyl radicals J. Rhys. Chem. 89 563-5... 

The sum of all results is consistent with the formation of both the aryl cation and the aryl radical in the aqueous acid system without copper, and with the dominance of the aryl radical in the presence of copper. The product ratios are also qualitatively consistent with the hypothesis that the reactivity of aryl cations with nucleophiles is close to that of a diffusion-controlled process (see Sec. 8.3), and that aryl radicals have arylation rate constants that are about two orders of magnitude smaller than that for diffusion control (0.4-1.7 X 107 m-1s-1 Kryger et al., 1977 Scaiano and Stewart, 1983). Due to the relatively low yields of these dediazoniations in the pentyl nitrite/benzene systems, no conclusions should be drawn from the results. 

In addition, Kozuka and Lewis measured the tritium isotope effect for the reaction between the n -hexyl, the 2-hexyl and the 2-methy 1-2-pentyl radicals with triphenyltin hydride and triphenyltin hydride-t see the last three entries in Table 11. The isotope effect of 2.55 found for the triphenyltin hydride-w-hexyl radical reaction was slightly smaller... 

Pentane gives 1-pentyl chloride as the main product, which is highly interesting as all other oxidative functionalisations will give a secondary alkyl derivative as the product, because for radical attack the secondary hydrogens are more reactive than the primary ones. 

A report considers the reactions of 1-butoxy and 1-pentoxy radicals with oxygen (eqs 1 and 2) and of their isomerizations by 1,5-H-shift (eqs 3 and 4) using direct and time-resolved monitoring of the formation of NO2 and HO radicals in the laser flash-initiated oxidation of 1-butyl and 1-pentyl radicals. ... 

The flash vacuum pyrolysis of alkynes, arynes, and aryl radicals has been reviewed. A discussion of secondary reactions and rearrangements is included. The pyrolysis of cyclopentadienes has also been examined. The rates for the initial C—H bond fission and the decomposition of C-C5H5 have been calculated. A single-pulse shock study on the thermal decomposition of 1-pentyl radicals found alkene products that are formed by radical isomerization through 1,4- and 1,3-hydrogen migration to form 2- and 3-pentyl radicals. The pyrrolysis of f-butylbenzene in supercritical water was the subject of a report. ... 

O3yhydroperoxides. Peroxides of the oxyhydro type are obtained by the addition of hydrogen peroxide to ketones. High yields of alkyl radicals are then often obtained by reaction with ferrous salts. 1-Meth-oxycyclohexyl hydroperoxide is easily obtained from cyclohexanone and hydrogen peroxide in methanol. It gives rise to the 5-(methoxy-carbonyl)-pentyl radical, which has been used to alkylate protonated heteroaromatic bases in high yield [Eq. (6)]. 

For pentyl radical, internal H-atom transfers can occur regardless of whether further oxidation occurs. These unimolecular reactions can directly compete with oxidation steps and so have implications for low-temperature combustion. For instance, n-pentyl radical can quickly isomerize to iso-pentyl radical via 1,4-H atom transfer each of these radicals can undergo p-scission reactions to yield a new alkyl radical + alkene ... 

Several experimental studies, over the past several decades, have modeled the overall combustion of this system. Jitariu et al. have calculated unimolecular rates for reactions of pentyl radical (i.e., intramolecular H-atom transfer, p-scission, and elimination) noting that isomerizations have lower barriers than p-scissions. ° ... 

In general, the trends predicted by -propylperoxy radical, 1-butoxy radical, and -pentyl radical provide good benchmarks for understanding the oxidation chemistry of longer chain radicals. For instance, 1,5-H-atom transfer and... 

Another radical 1,4-addition was reported by Giese and Roth. In the photoaddition of a 5-alkylidene-l,3-dioxan-4-one with pentyl iodide, mediated by Bu3SnH and di-/r /t-butyl peroxide (DTBP), a 95 5 mixture of diastereoisomeric dioxanones was obtained in 63% yield (Equation 31) <1996JBS243>. 

For amidyl radicals carrying a 6-hydrogen in the alkyl chain (e.g., XVII or N-pentyl, N-butyl, N-phenylbutyl analogues) intramolecular abstraction of the 6-hydrogen as in XVII and the collapse to 6-nitroso compound XVIII are very facile and occur preferentially within the radical pair (vide infra) over other... 

The alkyl radical ionization potentials needed were calculated by the pseudo-ir-orbital method.20 It was found21 that these radical ionization potentials converge to a constant value at the pentyl radicals. For various structures the values were as follows n-pentyl, 8.60 e.v. sec-pentyl, 7.81 e.v. iso-pentyl, 8.48 e.v. teri-pentyl, 7.19 e.v. (see ref. 21 for details of these calculations). The molecular ionization potentials also converge to a constant value at about ten carbons. Whenever these constant values are reached the heats of formation of the ions in Table II vary only with the heat of formation of the associated alkane, and therefore decrease by 5 kcal. mole-1 for each successive carbon atom. 

A 1,4 shift of this type was postulated by Duncan and Cvetanovid27 to explain some of their results on the reaction of CH2 with isobutene and butene-2. Previously, Gordon and McNesby56 demonstrated that intramolecular hydrogen abstraction occurs in the case of n-pentyl radicals ... 

Intramolecular abstraction of hydrogen by the intermediate alkoxy radical B to furnish the alkyl radical C always takes place through a six-membered transition state. In the photolysis of organic nitrites, no exception to this rule of six has been recorded to date. Thus, photolysis of 3-phenyl-l-propyl nitrite does not yield any product corresponding to attack on the a-carbon through a five-membered transition state (90), although abstraction of such a hydrogen should be exothermic to the extent of ca. 25 kcal./mole. 3 Also, irradiation of 5-phenyl-l-pentyl... 

Ylides (146) are cyclized by 30% aqueous hydrogen peroxide to afford the pyrido[ 1,2- ] azepines (147) (91HCA1095). The pyridof 1,2- ]azepinium system (148) is also obtainable by intramolecular free radical cyclization of 5-(l-pyridinio)-pentyl iodide (91T4077). 

The synthesis of mixed peroxides formed from /-butyl hydroperoxide and carbon-centred radicals has been studied. The reactions were strongly effected by solvents as well as catalytic amounts of Cun/Fem. The kinetic data suggest that the conditions for the Ingold-Fischer persistent radical effect are fulfilled in these cases.191 The use of Cu /Cu" redox couples in mediating living radical polymerization continues to be of interest. The kinetics of atom-transfer radical polymerization (ATRP) of styrene with CuBr and bipyridine have been investigated. The polymer reactions were found to be first order with respect to monomer, initiator and CuBr concentration, with the optimum CuBr Bipy ratio found to be 2 1.192 In related work using CuBr-A-pentyl-2-... 

---