2-methyl-2-propyl radical

Repeat your analysis for 2-methyl-2-propyl radical and 2-methyl-2-propyl anion, and assign preferred equilibrium geometry and the energy required to distort (by 10°) away from this geometry to each. 

Spin density surface for 2-methyl- 2-propyl radical shows the location of the unpaired electron. 

First examine the geometry of methyl radical. Is it planar or puckered Examine the geometries of 2 methyl-2-propyl radical, trifluoromethyl radical, triehloromethyl radical and tricyanomethyl radical. Classify each of the substituents (methyl, fluoro, chloro and cyano) as a 71-electron donor or as a 7t-electron acceptor (relative to hydrogen). Does replacement of the hydrogens by 7t-donor groups make the radical center more or less puckered Does replacement by Jt-acceptor groups make the radical center more or less puckered Justify your observations. 

Styrene, the most efficient quencher of triplet excited states of carbonyl compounds among a great variety of olefins employed by Ausloos and Rebbert (1964), gave no detectable influence on the ethene and carbon monoxide quantum yields when 20.1 Torr was added to 19.9 Torr of 2,2-dimethyl-3-hexanone (Nicol and Calvert, 1967). However, an almost quantitative removal of radical products of 1-propyl and 2-methyl-2-propyl radicals resulted. Since 4>co was unaffected by styrene addition, the radical... 

Alkyl radicals produced by oxidative decarboxylation of carboxylic acids are nucleophilic and attack protonated azoles at the most electron-deficient sites. Thus imidazole and 1-alkylimidazoles are alkylated exclusively at the 2-position (80AHC(27)241). Similarly, thiazoles are attacked in acidic media by methyl and propyl radicals to give 2-substituted derivatives in moderate yields, with smaller amounts of 5-substitution. These reactions have been reviewed (74AHC(i6)123) the mechanism involves an intermediate cr-complex. 

Simple alkyl radicals such as methyl are considered to be nonnucleophilic. Methyl radicals are somewhat more reactive toward alkenes bearing electron-withdrawing substituents than towards those with electron-releasing substituents. However, much of this effect can be attributed to the stabilizing effect that these substiments have on the product radical. There is a strong correlation of reaction rate with the overall exothermicity of the reaction. Hydroxymethyl and 2-hydroxy-2-propyl radicals show nucleophilic character. The hydroxymethyl radical shows a slightly enhanced reactivity toward acrylonitrile and acrolein, but a sharply decreased reactivity toward ethyl vinyl ether. Table 12.9 gives some of the reactivity data. 

Affinities toward other alkyl radicals have also been measured by Szwarc and his co-workers using techniques similar to those described above, It is interesting to compare the affinities of naphthalene with those of quinoline toward methyl, ethyl, and n-propyl radicals (Table X). 

On the basis of the reaction of alkyl radicals with a number of polycyclic aromatics, Szwarc and Binks calculated the relative selectivities of several radicals methyl, 1 (by definition) ethyl, 1.0 n-propyl, 1.0 trichloromethyl, 1.8. The relative reactivities of the three alkyl radicals toward aromatics therefore appears to be the same. On the other hand, quinoline (the only heterocyclic compound so far examined in reactions with alkyl radicals other than methyl) shows a steady increase in its reactivity toward methyl, ethyl, and n-propyl radicals. This would suggest that the nucleophilic character of the alkyl radicals increases in the order Me < Et < n-Pr, and that the selectivity of the radical as defined by Szwarc is not necessarily a measure of its polar character. 

For the 2-methyl-3-phenyl-3-(diphenylphosphatoxy)-2-propyl radical rate constants were obtained for the complete set of processes, including fragmentation to the contact ion pair, collapse of the contact ion pair to the rearranged... 

These radicals decompose according to the /3-scission rule, which implies that the bond that will break is one position removed from the radical site, so that an olefin can form without a hydrogen shift. Thus the isopropyl radical gives propene and a H atom, while the //-propyl radical gives ethene and a methyl radical. The /3-scission rule states that when there is a choice between a CC single bond and a CH bond, the CC bond is normally the one that breaks because it is weaker than the CH bond. Even though there are six primary CH bonds in propane and these are somewhat more tightly bound than the two secondary ones, one finds substantially more ethene than propene as an intermediate in the oxidation process. The experimental results [12] shown in Fig. 3.12 verify this conclusion. The same experimental effort found the olefin trends shown in Table 3.2. Note that it is possible to estimate the order reported from the principles just described. 

Radicals typically add to multiple bonds with little or no barrier, for example, methyl radical and ethylene to yield 1-propyl radical. 

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... 

A study of the photo-sensitized ring-opening reactions of the radical cations (76) of arylcyclopropanes (75) with methanol, water, and cyanide nucleophiles suggests a three-electron 5k2 mechanism (Scheme 11).185 The isolated products are methyl propyl ethers, derived from nucleophilic attack of methanol on the radical cation (76). They were detected by UV-VIS spectroscopy and shown to react with nucleophiles by transient kinetic methods. The benzyl radical (77) reacts with the DCB radical anion to afford monoaromatic ether (78) by oxidation and protonation or the disubstituted ether (79) by addition of DCB. Regio- and stereo-selectivity of the substitution were complete regiochemistry and rate constant were profoundly effected by the electronic nature of the aryl substituents.186 Elsewhere, a combined ab initio and CIDNP study... 

In our optical studies, two types of IR spectra have been obtained. The first one was measured for ARS with cations including the shortest alkyl radicals, namely, methyl-, ethyl- and iso-propyl-radicals (Fig.l, 2). For this... 

By varying the amount of chloroformste added per gram dextran different degrees of activation and derivatives of variable carbamate content could be prepared. In the NMR spectrum of the reaction product (IX) the methyl protons of the 2-hydroxy propyl radicals show up as a doublet at 6 = 1,3 ppm. From the integration values of the NMR signals the degree of modification was calculated. 

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... 

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