Ester carbonic

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). 

Like P—O—C linkages, P—O—P linkages are susceptible to hydrolytic degradation. Scrambling or interchange usually occurs for phosphoms oxyesters at temperatures and acidities lower than those required for the carbon esters but greater than those for the sulfur esters. 

Reaction of aHyl chloroformate and diethylene glycol in the presence of alkaU with cooling is another method of preparing the diallyl carbonate ester DADC. The properties of diallyl carbonate monomers are given in Table 1. 

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. 

Reaction with Water. The alkyl carbonate esters, especially the lower ones, hydroly2e very slowly in water when compared to the carbonochloridic esters (chloroformates). Under alkaline conditions, the rates of hydrolysis are similar to those of the corresponding acetic acid esters. 

Aiyl esters, prepared from the phenol and an acid chloride or anhydride in the presence of base, are readily cleaved by saponification. In general they are more readily cleaved than the related esters of alcohols, thus allowing selective removal of phenolic esters. 9-Fluorenecarboxylates and 9-xanthenecarboxylates are also cleaved by photolysis. To permit selective removal, a number of carbonate esters have been investigated aryl benzyl carbonates can be cleaved by hydrogenolysis aryl 2,2,2-trichloroethyl carbonates, by Zn/THF-H20. 

Both the chemical solubility and the electrical properties are consistent with those expected of a lightly polar polymer, whilst reactivity is consistent with that of a polymer containing hydrolysable carbonate ester linkages partially protected by aromatic hydrocarbon groupings. The influence of these factors on specific properties is amplified in subsequent sections. 

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. 

Aliphatic polycarbonates have few characteristics which make them potentially valuable materials but study of various aromatic polycarbonates is instructive even if not of immediate commercial significance. Although bisphenol A polycarbonates still show the best all-round properties other carbonic ester polymers have been prepared which are outstandingly good in one or two specific properties. For example, some materials have better heat resistance, some have better resistance to hydrolysis, some have greater solvent resistance whilst others are less permeable to gases. 

Reaction of the glycol (17) from hydroxylation of styrene with ethyl chloroformate affords the carbonate ester, 18. Treatment of this last with ammonia at elevated temperature gives the sedative, styramate (19)A similar sequence on the ethyl ana-... 

Condensation of prednisone, 40 with tetraethyl orthocarbonate leads to the cyelie ortho-carbonate 41 liydrolysis proceeds by protonation on the most accessible ether oxygen (that on carbon 21) to give the 17 mixed carbonate ester 42. Acylation with propionyl chloride proceeds on the remaining hydroxyl group to afford prednicarbate (43) [10],... 

Kohlensaure,/. carbonic acid carbon dioxide, -anhydrid, rt. carbonic anhydride (carbon dioxide), -ausscheidung,/. (Physiol.) c Tbon dioxide excretion, -bestimmer, m. apparatus for determining carbon dioxide, -brot, n, aerated bread, -chlorid, n. carbonyl chloride, -entwickelung,/. evolution of carbon dioxide, -ester, m. carbonic ester, -flasche, /. carbon dioxide cylinder, -gas, n, carbonic add gas (carbon dioxide), -gehalt, m. carbon dioxide content. 

Easily prepared from the appropriate monosaccharide, a glycal is an unsatu-rated sugar with a C1-C2 double bond. To ready it for use in potysaccharide synthesis, the primary -OH group of the glycal is first protected at its primary -OH group by formation of a silvl ether (Section 17.8) and at its two adjacent secondary - OH groups by formation of a cyclic carbonate ester. Then, the protected glycal is epoxidized. 

The thietanes are most often prepared through ring closure of 1,3-dibromides or 1,3-disulfonate esters1930 239,240, through fusion of cyclic carbonate esters of 1,3-diols with... 

The addition of alcohols to carbon disulfide in the presence of a base produces xanthates. The base is often OH, but in some cases better results can be obtained by using methylsulfinyl carbanion (MeSOCH ) If an alkyl halide RX is present, the xanthate ester ROCSSR can be produced directly. In a similar manner, alkoxide ions add to CO2 to give carbonate ester salts ROCOO. ... 

Production of carbonic esters can also take place via reactions between higher alcohols and CO2. These compounds find use in a variety of sectors, for example, organic synthesis, perfumes, pharmaceuticals, polymers, solvents, and lubricants [44]. 

Ostergaard, J., Hansen, S. H., Larsen, C., Schou, C., Heegaard, N. H. Determination of octanol-water partition coefficients for carbonate esters and other small organic molecules by microemulsion electrokinetic chromatography. Electrophoresis 2003, 24, 1038-1045. 

Ester groups can be removed readily by base-catalyzed hydrolysis. When basic hydrolysis is inappropriate, special acyl groups are required. Trichloroethyl carbonate esters, for example, can be reductively removed with zinc.208... 

Allyl carbonate esters are also useful hydroxy-protecting groups and are introduced using allyl chloroformate. A number of Pd-based catalysts for allylic deprotection have been developed.209 They are based on a catalytic cycle in which Pd° reacts by oxidative addition and activates the allylic bond to nucleophilic substitution. Various nucleophiles are effective, including dimedone,210 pentane-2,4-dione,211 and amines.212... 

Cyclic carbonate esters are easily prepared from 1,2- and 1,3-diols. These are commonly prepared by reaction with A.A -carbonyldiimidazole214 or by transesterification with diethyl carbonate. 

Several other nucleophilic functional groups can be induced to participate in iodocyclization reactions. t-Butyl carbonate esters cyclize to diol carbonates.79... 

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