Carbon radical displacement

At elevated pressure, the partial pressure of carbon dioxide inhibits calcination, and siilfur dioxide is captured by displacement of the carbonate radical. The overall effect is similar except, as no free hme is formed, the resulting sorbent ash is less alkahne, consisting solely of CaS04 and CaC03. 

Syntheses are limited to mercuric salts of weak acids (2,110). Generally, increasing the length of the straight alkyl chain decreases the extent of decarboxylation (e.g., Ref. 133). Electron-withdrawing substituents suppress decarboxylation. For example, mercurials are not formed with Me02C, Cl, and Me(CH2)nO substituents on the a carbon (137,148,149), but some decarboxylation occurs with these on the j8 carbon (135-137). Chain decarboxylation predominated in reactions in benzene, butyric acid [R = Me(CH2)2] (150), or acetic acid (R = Me) (124). The chain reaction was also observed for R = Me(CH2)2 in the absence of solvent and in ethylacetate or heptane solution, but in these media the radical displacement reaction was dominant (2,150). When benzene was used as solvent... 

The orbital requirements for radical attack on any polyene are given in Table 6. If H3, HC2 and Cl8 (see Walsh diagram, Fig. 2) can be taken as models, then three-center transition states will be linear. If, however, cyclic transition states can be formed, HMO theory indicates a preference for them (Fig. 1). Unfortunately, attempted radical displacements have not been observed, simply because the radicals take other reaction paths (Pryor, 1966). The transition states may have been linear, but for abstraction from rather than displacement on carbon (Bujake et al., 1961). If the radical and molecule generated in these cases remain in... 

Loss of formaldehyde from radicals RCH2O occurs when R is relatively stable it has been implicated as a consequence of O-N fission of the 6-nitrates of nitrocellulose, where the product radical is essentially anomeric. " " Thermolysis of 2,2-dimethyl-1,3-propanediol dinitrate yields 2,2-dimethyloxirane by N-O homolysis, loss of CH2O and displacement of NO2 from oxygen by the tertiary carbon radical (Figure 6.44). A similar mechanism also appears to take place during PETN thermolysis, whose products are NO2, formaldehyde and a condensation polymer of isolactic acid. 

Carbon radicals generated by the polymerization of methyl methacrylate do not undergo displacement reactions with the Sn-S, Sn-O, Sn-C, or Sn-Cl bonds of typical organotin stabilizers (73). However, PVC stabilization caused by scavenging of chlorine atoms by organotins has not been ruled out experimentally (73). Furthermore, the ability of... 

The presence of excess tetrafluoroethylene promotes reaction of the fluorocarbon radical end of 1 with another molecule of tetrafluoroethylene to form a new diradical, 2. Stabilization of 2 occurs by intramolecular attack of the carbon radical end on sulfur with formation of a favored thiolane ring, 3, and displacement of the sulfur chain. Yields of 20% of 3 have been attained. 

Various explanations have been given such as stepwise cleavage of the two C-N bonds with concerted backside displacement of the nitrogen molecule by the carbon radical and, intriguingly, conservation of momentum upon loss of dinitrogen that results in the double inversion product. This latter explanation has been pursued by Carpenter who has championed non-statistical dynamics as an explanation for many stereochemical pathways in thermal reactions. ... 

Radical displacement on carbon is extremely rare, excluding examples in which a strained ring is cleaved. One case that has been claimed involves the formation of cyclopropane from the 3-iodo-1-propyl radical (eq. 22). The mechanism in eq. 22 has been criticized (52) on the basis of the high strain generated in the... 

Replacement of Labile Chlorines. When PVC is manufactured, competing reactions to the normal head-to-tail free-radical polymerization can sometimes take place. These side reactions are few ia number yet their presence ia the finished resin can be devastating. These abnormal stmctures have weakened carbon—chlorine bonds and are more susceptible to certain displacement reactions than are the normal PVC carbon—chlorine bonds. Carboxylate and mercaptide salts of certain metals, particularly organotin, zinc, cadmium, and antimony, attack these labile chlorine sites and replace them with a more thermally stable C—O or C—S bound ligand. These electrophilic metal centers can readily coordinate with the electronegative polarized chlorine atoms found at sites similar to stmctures (3—6). 

It resembles tetracyanoethylene in that it adds reagents such as hydrogen (31), sulfurous acid (31), and tetrahydrofuran (32) to the ends of the conjugated system of carbon atoms suffers displacement of one or two cyano groups by nucleophilic reagents such as amines (33) or sodiomalononittile (34) forms TT-complexes with aromatic compounds (35) and takes an electron from iodide ion, copper, or tertiary amines to form an anion radical (35,36). The anion radical has been isolated as salts of the formula (TCNQ) where is a metal or ammonium cation, and n = 1, 1.5, or 2. Some of these salts have... 

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluorinated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloto-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlorine shifts to afford perfluonnated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluorination of 3-chloropentane [7] (equation 1). Aerosol fluorina-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4 (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachlonde, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

The synthesis of the trismethylenemethane iron tricarbonyl complex [(CH2)3C]-Fe(CO)3 was reported by Emerson et al. in 1966 (27). The geometry of this compound in the gas phase was investigated by Almenningen et al. (28) using electron diffraction methods. These authors pointed out some structural peculiarities which were not amenable to a simple explanation, in particular, why the hypothetical planar (CH2)3C radical is distorted when bound to the Fe(CO)3 conical fragment in such a way that the carbon atoms of the CH2 groups are displaced toward — the iron atom (Fig. 9). 

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