Carbon compounds stabilization

Over the next two years, Midgley and his group discovered and patented other chlorofluorocarbons and the halons, a class of bromofluoro-carbon compounds that are the world s best Are fighters. At the time, their remarkable stability seemed like an advantage. In the 1970s scientists were able to determine that CFCs and halons—which are so stable that they remain in the atmosphere for long periods of time—deplete the ozone layer 15 miles above Earth. 

Keywords spatial-energy parameter, compound stabilization, carbon nanostructures. 

Abstract The theoretical and experimental research on carbodiphosphoranes C(PR3)2 and related compounds CL2, both as free molecules and as ligands in transition metal complexes, is reviewed. Carbodiphosphoranes are examples of divalent carbon(O) compounds CL2 which have peculiar donor properties that are due to the fact that the central carbon atom has two lone electron pairs. The bonding situation is best described in terms of L C L donor acceptor interactions which distinguishes CL2 compounds (carbones) from divalent carbon(ll) compounds (carbenes) through the number of lone electron pairs. The stmctures and stabilities of transition metal complexes with ligands CL2 can be understood and predictions can be made considering the double donor ability of the carbone compounds. 

The number of bisylides, in which the carbon atom is stabilized by two neutral sulfur compounds, is restricted so far to one example, C(S NMe Ph2)2, with sulfur (IV). The proton of the conjugated acid (HC(S NMe Ph2)2) can be reversibly removed on an ion exchange resin loaded with OH protonation is achieved with 10% HCIO4 in methanol as shown in Fig. 8. The bent structure with an S-C-S angle of 117° and bond shortening of the C-S bond upon deprotonation of the related cation proves this compound as a typical carbon(O) compound stabilized by the Lewis base S(NMe)Ph2. Although the compound was reported to be stable even... 

Treatment of y-nitro alcohols with diethyl azodicarboxylate DEAD and triphenylphos-phine affords nitrocyclopropanes with inversion of configuration at the a-carbon via the intramolecular Mitsunobu reaction involving carbon nucleophiles stabilized by the nitro group (equation 16)28. The reaction works best with nitro compounds (pA"a < 17) and is not applicable to the sulfonyl derivatives (pATa 25). 

Electron-withdrawing substituents generally increase diazo compounds stability toward decomposition. Dicarbonyl diazomethane, which bears two carbonyl groups flanking the diazomethane carbon, are more stable than diazo compounds with only one carbonyl substituent. In general, metal catalysed decomposition of dicarbonyl diazomethane requires higher temperature than does monocarbonyl substituted diazomethane. As indicated before, rhodium(II) carboxylates are the most active catalysts for diazo decomposition. With dicarbonyl diazomethane, the rhodium(II) carboxylate-promoted cyclopropanation process can also be carried out under ambient conditions to afford a high yield of products. 

An enormous variety of r-bonded systems, whether they be neutral or ionic, cyclic or linear, odd or even in the number of carbon atoms, serve as ligands that coordinate to transition metals. Figure 14.3.1 shows some representatives of the innumerable organometallic coordination compounds stabilized by metal-TT bonding. 

They are much more reactive than corresponding carbon compounds and will inflame spontaneously in air. Stability decreases with chain length in series such as... 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, silicon, and sulfur are not included these are of interest, however, because of their stability at high temperatures. A large number of ternary compounds, including numerous oxyhalides, and more complicated compounds have been synthesized and characterized. These include many intermediate (nonstoicliiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teflurates, tellurites, selenides, and tellurides. 

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