Structural properties phosgene

The electronic structure of phosgene has been discussed in some detail in Chapter 17, its photochemical synthesis is described in Section 5.1.1, and its photochemistry has been briefly discussed elsewhere [1551]. However, a brief summary of the pertinent properties would not be inappropriate at this juncture. 

The chemical structure is depicted below, and the physicochemical properties of phosgene are presented in Table 1-2. 

Isocyanates are compounds with the general formula R-N=C=0. They have numerous uses in chemical synthesis, particularly in the manufacture of polymers with carefully tuned specialty properties. Methyl isocyanate is a raw material in the manufacture of carbaryl insecticide. Methyl isocyanate (like other isocyanates) can be synthesized by the reaction of a primary amine with phosgene in a moderately complex process, represented by reaction 15.8.1. Structures of three significant isocyanates are given in Figure 15.7. 

Phosgene proved to be an appropriate reactant to remove aluminium from the zeolite framework [1,2]. Detailed measurements have been carried out to investigate the adsorption of phosgene [3], the mechanism of dealumination by infrared spectroscopic and thermogravimetric methods [4], structural consequences [5], adsorption and catalytic properties of modified mordenites [6]. In addition an NMR study has been carried out, to measure the thermal stability of so-called hydroxy nests in H-mordenite dealuminated with phosgene [7]. 

Various processes are technically available for PC manufacture, but the one used almost exclusively at present is phase boundary interfacial polymerization [94], With this method, PC can be made very economically from phosgene and bisphenol A, and its properties profile can be varied widely. Thus, molecular weight, structural uniformity and the PC structure itself can be modified and tailored to the needs of the application and the processing method. 

The aldehyde XXXIII was converted by phosgene into the vinylogous imidoyl chloride XXXIV which was condensed with 4a-methylhexahy-drocarbazole XXXV in the presence of base to give the product XXXVI isolated and characterized as its yellow crystalline perchlorate. A series of related compounds was also prepared am I the properties and spectra of the whole group of substances gives strengtJ i to the assigned structures. 

The properties of polyurethanes also depend on the structure of the isocyanate component. Isocyanates are prepared by phosgenation of the corresponding ammonium salt. Poly/diisocyantes used for synthesising polyurethanes are generally aromatic, aliphatic, cycloaliphatic or polycyclic in structure. The most commonly used diisocyanates with their abbreviated names are listed in Table 6.2. 

Polycarbonates are well known to be typical amorphous polymers and to have excellent properties such as heat resistance, impact resistance, transparency, and dimensional stability (2-5). Polycarbonates, therefore, have been widely employed in various applications from nursing bottles to precision instruments (CDs, cameras, etc.), or in structural materials (for electrical applications, electronics, automobiles, construction applications, etc.). The global demand of polycarbonates has been growing more than 10% per year. The production capacity of polycarbonate world wide is about 1 million tons per year, and the boom in polycarbonate plant construction continues. Almost all of the polycarbonates, however, have been produced by the Phosgene Process . 

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