Phosgene carbonate esters

Rea.ctlons, The chemistry of butanediol is deterrnined by the two primary hydroxyls. Esterification is normal. It is advisable to use nonacidic catalysts for esterification and transesterification (122) to avoid cycHc dehydration. When carbonate esters are prepared at high dilutions, some cycHc ester is formed more concentrated solutions give a polymeric product (123). With excess phosgene the usefiil bischloroformate can be prepared (124). 

The reaction of phosgene (carbonic dichloride [75-44-5]) with alcohols gives two classes of compounds, carbonic esters and carbonochloridic esters, commonly referred to as carbonates and chloroformates. The carbonic acid esters (carbonates), R0C(0)0R, are the diesters of carbonic acid [463-79-6]. The carbonochloridic esters, also referred to as chloroformates or chlorocarbonates, C1C(0)0R, are esters of hypothetical chloroformic acid [463-73-0] CICOOH. 

More recendy, preparation of carbonic esters by nonphosgene routes, such as the reactions of CO or CO2 with appropriate substances in the presence of catalysts, has been preferred. These methods are more economic in many cases and naturally less ha2ardous than phosgene routes. 

Unless the hydroxyl groups have such proximity that cyclisation takes place, polycarbonates will normally be produced whenever phosgene or a carbonate ester is reacted with a polyhydroxy compound. This means that a very large range of polycarbonate resins are possible and in fact many hundreds have been prepared. 

When phosgene is used, the carbonic ester derivative formed in the reaction cyclizes by regenerating one molecule of amidoxime 115). 

Nemirowsky, in 1883, reported the preparation of the cyclic carbonate ester I from ethylene glycol and phosgene, and, in 1909, Siegfried and... 

Reaction of 1,2-diaminoarenes with phosgene or urea gives 2-benz-imida/.olones (Scheme 3.1.14). The latter reagent has been preferred as it is less toxic. There are, however, a variety of other reagents which lead to the same products carbonate esters [117], diethyl pyrocarbonatc [118], N,N-diethylcarburnyl chloride [119], l,T-carbonyldiimidazole [120], cyanic acid [121] and carbon dioxide [122]. (See also reactions with ketones below.) Preston has reviewed these processes [54]. The reactions with urea (or... 

Diethyl esters of -alkylamino phosphoric acid react readily with phosgene. Carbon dioxide and chloroethane are liberated, reaction occurring at the phosphoryi group in preference to the nitrogen atom [508] ... 

Transesterification of diphenyl carbonate and bisphenol A. The final step in the nonphosgenation process for polycarbonates is the reaction of bisphenol A (BPA) and the carbonate ester, diphenyl carbonate (DPC). Research has focused on the transesterification melt process because it has the advantage over the conventional interfacial process of allowing the reaction of the diphenyl carbonate and bisphenol A to take place completely in the liquid phase. The disadvantage of this approach is that elevated temperatures are needed to ensure that unreacted DPC and BPA are completely volatilized from the product. Only a lower molecular weight (30,000-50,000) polymer can be made in this way. Typical molecular weights for polycarbonate produced by phosgenation in the interfacial pro-... 

Cyclic carbonate esters are easily prepared from uic-diols and can be used in a complementary fashion to the cyclic acetals previously described. These esters are commonly prepared from N,N -carbonyldiimidazole or by transesterification using diethyl carbonate. These reagents are preferable to phosgene both in efficiency and convenience. 

Carbonic acid is a diacid with suitable diols, it can form polyesters. For example, when phosgene (the acid chloride of carbonic acid) reacts with a diol, the product is a poly(carbonate ester). The following equation shows the synthesis of Lexan polycarbonate a strong, clear, and colorless material that is used for bulletproof windows and crash helmets. The diol used to make Lexan is a phenol called bisphenolA, a common intermediate in polyester and polyurethane synthesis. 

Carbonothioic acid, 0-(6-chloro-3-phenyl-4-pyridazinyl) S-octyl ester. See Pyridate, Carbonothioic dichloride. See Thiophosgene Carbon oxide. See Carbon monoxide Carbon oxide sulfide. See Carbonyl sulfide Carbon oxychloride. See Phosgene Carbon oxysulfide. See Carbonyl sulfide Carbon silicide. See Silicon carbide Carbon sulfide. See Carbon disulfide Carbon tet. See Carbon tetrachloride Carbon tetraboride. See Boron carbide Carbon tetrabromide CAS 558-13-4 EINECS/ELINCS 209-189-6 UN 2516... 

Phosgene is an intermediate in the chemical industry for the production of di-iso cyanates, polycarbonate plastics, chloroformic esters, carbonate esters, dyes [13] etc. Phosgene is produced from carbon monoxide and chlorine... 

High molecular weight, lightstabUizir compounds for imparting improved resistance to ultraviolet radiation to polycarbonate-based polymers are prepared by interfacial condensation of phosgene or its derivatives or carbonate esters with bisphenol derivatives [270]. 

There are two main methods for the manufacture of poly(2,2-bis(4 -phenyl-ene)propane carbonate), namely direct phosgenation and ester interchange. 

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