Isopropyl free radical

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... 

DIITIATORS - FREE-RADICAL INITIATORS] (Vol 14) p-Isopropyl-N,Ndimethylben2amide [6955-06-2]... 

The most common poly(alkenoic acid) used in polyalkenoate, ionomer or polycarboxylate cements is poly(acrylic acid), PAA. In addition, copolymers of acrylic acid with other alkenoic acids - maleic and itaconic and 3-butene 1,2,3-tricarboxylic acid - may be employed (Crisp Wilson, 1974c, 1977 Crisp et al, 1980). These polyacids are prepared by free-radical polymerization in aqueous solution using ammonium persulphate as the initiator and propan-2-ol (isopropyl alcohol) as the chain transfer agent (Smith, 1969). The concentration of poly(alkenoic add) is kept below 25 % to avoid the danger of explosion. After polymerization the solution is concentrated to 40-50 % for use. 

Free radical polymerization combined with anionic ring polymerization was employed for the synthesis of poly(N-vinylpyrrolidone)-fr-poly(D,L-lactide), PVP-fr-PDLLA, as shown in Scheme 49 [121]. The free radical polymerization of VP was conducted using 2,2/-azobis[2-methyl-M-(2-hydroxyethyl)propionamide] as the initiator, isopropyl alcohol and 2-... 

The predominance of isopropyl alcohol over n-propyl alcohol is readily explained since abstraction of the secondary H atoms in propane by free radicals will be easier than abstraction of the primary H atoms,... 

Assuming the relative rate of secondary to primary hydrogen atom abstraction to be the same in the chlorination of propane as it is in that of butane, calculate the relative amounts of propyl chloride and isopropyl chloride obtained in the free-radical chlorination of propane. 

Terpenoid Synthesis from Isoprene.—Interest continues in new syntheses of iso-prene and its derivatives the dioxan (37) is obtained108 in good yield by the Prins reaction of methylallyl chloride with formaldehyde (cf. Vol. 5, p. 8) free-radical addition of isopropyl alcohol to vinyl acetate yields compound (38) which gives isoprene by acid-catalysed reaction over alumina.109 (Z)-2-Methylbut-2-en-l-ol and dimethylallyl alcohol are readily available from frans-crotyl alcohol.110... 

The a-position of an ether is susceptible to attack by free radicals and, in certain circumstances, by halogens. Ethers are slowly oxidized by the oxygen from air to form peroxides- This can be a hazard in stored bottles of ethers, particularly with the higher ethers such as di-isopropyl ether. These peroxides may be destroyed by treatment with iron(IT) sulfate. Chlorine reacts with ethers, particularly in sunlight. These a-halo ethers then decompose to the aldehyde and an alcohol. 

In contrast to the tertiary alcohols, primary (e.g., ethyl alcohol) and secondary alcohols e.g., isopropyl alcohol) decompose to products at temperatures above 800 °K via complex free radical chain processes . This mechanistic inversion is not surprising. Based on the magnitude of substituent effects in four-center elimination reactions, particularly the variations found in the series r-BuCI, i-PrCl, EtCl - , one would estimate that the isopropyl alcohol unimolecular elimination of water should have an activation energy about 6 kcal.mole higher than that for r-butyl alcohol. The. 4-factor can be estimated by transition state methods, and one obtains for the unimolecular decomposition... 

Now, by selectivity we mean here the differences in rate at which the various classes of free radicals are formed a more stable free radical is formed faster, we said, because the factor that stabilizes it—delocalization of the odd electron (Sec. 6.28)—also stabilizes the incipient radical in the transition state. If this is so, then the more fully developed the radical character in the transition state, the more effective delocalization will be in stabilizing the transition state. The isopropyl radical, for example, is 3 kcal more stable than the Ai-propyl radical if the radicals were completely formed in the transition state, the difference in act would be 3 kcal. Actually, in bromination the difference in act is 3 kcal equal, within the limits of experimental error, to the maximum potential stabilization, indicating, as we expected, a great deal of radical character. In chlorination, by contrast, the difference in is only 0.5 kcal, indicating only very slight radical character. 

Free-radical chlorination of either w-propyl or isopropyl bromide gives 1-bromo-2-chloropropane, and of either isobutyl or / r/-butyl bromide gives l-bromo-2-chloro-2-methylpropane. What appears to be happening Is there any pattern to this behavior ... 

Ionic addition yields isopropyl bromide because a secondary cation is formed faster than a primary. Free-radical addition yields w-propyl bromide because a secondary free radical is formed faster than a primary. Examination of many cases of anti-Markovnikov addition shows that orientation is governed by the ease of formation of free radicals, which follows the sequence 3° > 2 > T. 

Pyrolysis of poly(4-vinyl pyridine) was demonstrated to be a free radical process. Both poly(vinyl pyridines) generate as a main pyrolysis product the monomer, 2-ethenylpyridine or 4-ethenylpyridine, respectively. In the pyrogram of poly(2-vinyl pyridine), the dimer is also present (30% of the peak area). This peak is not seen in the pyrogram of poly(4-vinyl pyridine), but it is possible that the compound exists and elutes at a longer retention time than the one used in the chromatographic conditions applied for the pyrolysate separation. Other pyrolysate components not shown in Table 6.5.11 or 6.5.13 were reported in literature. Among these are propenylpyridine, isopropyl-pyridine, isoquinoline, phenylpyridine, 4,4 -dipyridyl, 4-[2-(4-pyridyl)ethyl]pyridine, 4-[2-(4-pyridyl)ethenyl]pyridine, 4-[3-(4-pyridyl)propyl]pyridine, etc. [39]. Similarly to the case of polystyrene, the H-T polymerization is prevalent in poly(vinylpyridine). However, some H-H units can be present in the polymer, and their abundance can be estimated from Py-GC/MS data. 

Photoexcited ketones can undergo other reactions typical of free radicals. Benzophenone dissolved in isopropyl alcohol undergoes a pinacol coupling merely upon exposure to sunlight. The /-PrOH acts as a hydrogen atom donor. 

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