Addition reactions continued functionalized

Phosgene addition is continued until all the phenolic groups are converted to carbonate functionalities. Some hydrolysis of phosgene to sodium carbonate occurs incidentally. When the reaction is complete, the methylene chloride solution of polymer is washed first with acid to remove residual base and amine, then with water. To complete the process, the aqueous sodium chloride stream can be reclaimed in a chlor-alkali plant, ultimately regenerating phosgene. Many variations of this polycarbonate process have been patented, including use of many different types of catalysts, continuous or semicontinuous processes, methods which rely on formation of bischloroformate oligomers followed by polycondensation, etc. 

The selective oxidation of C—H bonds in alkanes under mild conditions continues to attract interest from researchers. A new procedure based upon mild generation of perfluoroalkyl radicals from their corresponding anhydrides with either H2O2, m-CPBA, AIBN, or PbEt4 has been described. Oxidation of ethane under the reported conditions furnishes propionic acid and other fluorinated products.79 While some previously reported methods have involved metal-mediated functionalization of alkanes using trifluoroacetic acid/anhydride as solvent, these latter results indicate that the solvent itself without metal catalysis can react as an oxidant. As a consequence, results of these metal-mediated reactions should be treated with caution. The absolute rate constants for H-abstraction from BU3 SnH by perfluorinated w-alkyl radicals have been measured and the trends were found to be qualitatively similar to that of their addition reactions to alkenes.80 a,a-Difluorinated radicals were found to have enhanced reactivities and this was explained as being due to their pyramidal nature while multifluorinated radicals were more reactive still, owing to their electrophilic nature.80... 

In Chapter 11 we continue our focus on organic molecules with electron-rich functional groups by examining alkynes, compounds that contain a carbon-carbon triple bond. Like alkenes, alkynes are nucleophiles with easily broken n bonds, and as such, they undergo addition reactions with electrophilic reagents. 

The generation sequence of the most intense photoproduct series is shown in Fig. 5 by the integral absorptions of the individual photoproducts as a function of the irradiation time. Only the photoproduct A is generated without any delay. In the sequence B, C, D,. .. the induction period increases continuously. This corresponds to the expected polymerization reaction starting with the formation of the dimer A followed by subsequent addition reaction steps to the trimer B and tetramer C molecules etc. The curves are calculated using the kinetic expressions described below. 

Diels-Alder Cycloadditions.—The range of functionalized diene systems, displaying regioselective behaviour in the Diels-Alder reaction, continues to expand. Notable new additions include l-phenylseleno-2-trimethylsilyloxy-4-methoxybuta-l,3-diene (82) and the isomers 1- and 2-methyl-l,3-bis(trimethylsilyloxy)buta-l,3-dienes (84) and (85). The diene (82) is readily derived from l-methoxy-3-trimethylsilyloxybuta-1,3-diene (81) and provides a direct route to the synthetically valuable 4-acylcyclohexa-2,5-dienones (83), whereas dienes (84) and (85) react with activated dienophiles (e.g. RCH=CHC02Et) in good yield, leading to keto-esters of the type (86) on hydrolysis. 

The values of the real systems, obtained from experiments at pressures up to 50 bar, may be extrapolated to still higher pressures since E = f(P) and log A = f(F) are continuous functions. The supply of oxygen in the oxidation experiments at 50 bar pressure is sufficient to ensure attainment of the asymptotic limits at least in the first reaction step (LTO). Evaluation of the second reaction step of the oxidation (fuel deposition) is more difficult because an increase of the heating rate provokes the occurrence of additional peaks, which will be flattened as a consequence of a rise of the pressure. For the consecutive and parallel oxidation and pyrolysis reactions in this step, overall values of E and log A have been found, which only give steady functions for the vacuum residue. The data of the last reaction step (fuel combustion) may be evaluated very easily. They also give steady functions for E = f(P) and log A = f(P). All substances tested behave similarly to activated carbon (charcoal). Only the coke residue of -hexylpyrene reacts completely differently and demonstrates different curves in the plots of the reaction rate constant and the half life time versus the pressure. In this reaction step the curves did not reach the asymptote even at pressures of 50 bar, but they may be extrapolated to higher pressures. 

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