Chlorocarbonate radical

In the same manner, other triphenylmethyl chlorocarbon radicals have been synthesized, including perchloro-p-phenyltriphenylmethyl (PPTM ), perchloro-/ ,/ -diphenyltriphenylmethyl (PDTM-) and perchloro-/>,/>, />"-tri-phenyltriphenylmethyl (PTTM ). They all display the same extremely high chemical inertness and thermal stability. Nearly one hundred perchlorinated radicals have been synthesized by Ballester and coworkers. Before the discovery of these radicals, the most stable carbon free radical was 2-(4-biphenylyl)bis(biphenylenyl)allyl, described by Kuhn and Neugebauer (1964) its half-life in air, in solution and at room temperature, is about 10 h. 

These pyridine-substituted trivalent-carbon radicals are perfectly stable in air, even in solution. The PTM-like (2Py—PDM- and 4Py—PF ) and the PPF-like radicals are truly IFRs, in spite of weaker steric shielding of their trivalent carbon. They behave chemically like their chlorocarbon-radical analogues, and react with oleum and with HNO3 like them, giving p-quinonoid structures (pp. 359, 369). 

The most common reaction of methylene chloride is its reaction with chlorine to give chloroform and carbon tetrachloride. This occurs by a free-radical process initiated by heat or light in the gas or Hquid phase. Catalytic chlorination to these same products is also known (see Chlorocarbons and Cm OROHYDROCARBONS, Cm OROFORM). 

That this mode may exist was shown (65) by observing an increase in system photospeed on addition of a chlorocarbon which could scavenge tin radicals and yield an additional initiating carbon-centered radical by chain transfer ... 

The silaylides formed from coordination of silylenes to chlorocarbons are believed to undergo competitive rearrangement (to the formal Cl—C insertion product) and fragmentation (to the product of formal HC1 abstraction by the silylene)5. In addition, these silaylides are believed to undergo dissociation into the radical pairs that would result from direct chlorine atom abstraction by the silylene111. 

The ESR signals are complex and overlapping and are probably derived from at least two radical species. The radicals have been identified as silicon centered, on the basis of their g values, the observation of a Si hyperfine interaction, and their reactivity with oxygen and chlorocarbons. In no case, however, was a persistent-radical signal observed that is split by four equivalent a hydrogens, as would be expected for a radical produced by simple chain scission. 

Most of the photoreactions of dimeric Co carbonyls involve cluster formation or cross coupling with other dimers. Compared to other metal-carbonyl radicals, Co(CO) is much less reactive COjCCO) is inert to irradiation in the presence of IC,H,. Even if the expected ICo(CO) were formed, its thermal instability would lead to problems. Irradiation in chlorocarbons produces Co3(CO),CCl in low yield. Under conditions where CO can be removed from solution, irradiation of COjCCO), in inert solvents leads to Co fCO) A likely mechanism involves CO loss from Co(CO) fragments that recombine to yield a transient, unsaturated dimer, which reacts with Co fCO), to give tetramer and CO. 

Beilstein Handbook Reference) AI3-26269 BRN 0506416 Carbonochloride acid, 1-methylethyl ester Carbonochloridic acid, 1-methylethyl ester Chloroformic acid isopropyi ester EiNECS 203-563-2 Formic acid, chloro-, isopropyl ester HSDB 2848 Isopropyl chlorocarbonate Isopropyl chloroformate Isopropyl chloromethanoate Isopropylester kyseliny chlormravenci UN2407. Chemical intermediate for free-radical polymerization initiators, also used in organic synthesis. Liquid bpn 105° soluble in EtzO. BASF Corp. ElfAtochem N. Am. PPG Ind. 

Inert free diradicals and ions derived from them 394 Perchloro nitrogen-centred radicals 399 Spectroscopy of chlorocarbons 405 Electronic absorption spectra 405 Infrared spectra 423... 

The radical p—CCI3—C6CI4—CC 2 (CCI3—PB ) has been detected as an intermediate in reductive polymerization of perchloro-p-xylene, giving the polymeric chlorocarbon PP-xynene (p. 304) (Doorenbos, 1969). 

PTM- in solution is also light-sensitive (Ballester, 1967), its disappearance having been monitored by ultraviolet/visible spectrometry. Under the suspicion that perchloro-9-phenylfluorenyl radical (PPF-) is formed, the illumination was performed in carbon tetrachloride in the presence of CI2 as a radical scavenger, and accordingly some perchloro-9-phenylfluorene was obtained, among other chlorocarbons (171) (Badia, 1969). The esr signal... 

The infrared spectra of some other types of highly chlorinated aromatic compounds (a//-quasiperchloro compounds, perchloro-di- and triphenyl-methyl radicals, fused polycyclic aromatic chlorocarbons, aromatic chloro-carbon ions) have also been recorded and reviewed (Ballester et al., 1978c). 

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