Bischloroformate

The hydroxyl groups can be esterified normally the interesting diacrylate monomer (80) and the biologicaky active haloacetates (81) have been prepared in this manner. Reactions with dibasic acids have given polymers capable of being cross-linked (82) or suitable for use as soft segments in polyurethanes (83). Polycarbamic esters are obtained by treatment with a diisocyanate (84) or via the bischloroformate (85). 

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). 

Phosgene addition is continued until all the phenoHc groups are converted to carbonate functionahties. 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-alkah 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. 

A newer process for preparation of mixtures of cycHc oligomers has been discovered (15,35). This process utilizes a triethylamine-catalyzed hydrolysis condensation of BPA bischloroformate in a pseudo-dilution reaction. This efficientiy provides 85—90% yield of a mixture of cycHc oligomers having a degree of polymeriza tion of 2 to about 12 (eq. 12). 

Polyurethanes (PURs) are usually described as being prepared by the reaction of diols with diisocyanates. However, this is an oversimplification because often water is deliberately added in the production of flexible polyurethane foams. Unreacted isocyanate groups react with water to form carbon dioxide and urea groups in the polymer chain. The carbon dioxide acts as a blowing agent in the production of PUR foams. Also, polyurethanes can be formed by the reaction of bischloroformates with diamines. 

A lV -Bis p-carbomethoxy benzoyl) butanediamine (T4T-dimethyl), synthesis of, 107-108 Bischloroformates, reaction with dicarboxylic acids, 87 Bis(4-chlorophenyl)phenyl phosphine oxide (BCPPO), 345... 

Anionic polymerization of lactams was shown to proceed according to what is called the activated monomer mechanism. With bischloroformates of hydroxy-terminated poly(tetramethyleneglycol) and poly(styrene glycol) as precursors for a polymeric initiator containing N-acyl lactam ends, block copolymers with n-pyrrol-idone and e-caprolactam were obtained by bulk polymerizations in vacuum at 30 and 80 °C, respectively361. ... 

PLLA-fr-PCL) multiblock copolymers were prepared from the coupling reaction between the bischloroformates of carboxylated PLLA with diol-terminated PCL in the presence of pyridine [140]. LLA was polymerized with SnOCt2 and 1,6-hexanediol followed by the reaction with succinic anhydride to provide the dicarboxylated PLLA. The carboxyl end groups were subsequently transformed to acid chloride groups by the reaction with thionyl chloride (Scheme 65). As expected, the molecular weight distributions were broad for all samples (1.84 < Mw/Mn < 3.17). 

Ethylenebis(hydroxyphenylglycine), molecular formula, 5 712t EthylenebisCtetrabromophthalimide), 11 468 physical properties of, 4 355t Ethylene bischloroformate molecular formula, 6 291t toxicity, 6 302t Ethylenebisdibromonorbor-... 

Mahood et al. (3) prepared co-polycarbonates having TH s > 250°C by reacting cyclohexane-bisphenol, (III), and phosgene capped with bischloroformate. 

Bisphenol-A is present as the disodium salt in the aqueous phase of the two-phase mixture. Phosgene enters the system and dissolves in the organic phase. It is believed that the reaction between phosgene and bisphenol-A occurs at the organic-aqueous interface to form the monochloroformate—Reaction 1—or bischloroformate—Reaction 2— ester of bisphenol-A. The chloroformate esters that form grow to oligomers by reaction with additional bisphenol-A or by self-condensation —Reactions 3 and 4, respectively. 

The degree of polymerization of bischloroformate oligomers prepared in the pyridine system is controlled primarily by the molar ratio of phosgene to bisphenol-A, as long as the ratio is greater than 1. Increas-... 

Figure 2. GPC curves for bisphenol-A oligomer bischloroformates prepared by the interfacial technique at the reaction temperatures and stirrer speeds shown...

Analysis of Bisphenol-A Carbonate Oligomers for Chloroformate Chlorine. Chloroformate chlorine end groups were determined by a modified Volhard procedure in which the bischloroformate first reacts with aqueous pyridine to convert chloroformate to chloride ion. The chloride ion is extracted into water and titrated by the Volhard procedure. 

The various peaks in Figure 2 occur often in GPC analysis of bis-phenol-A oligomer bischloroformates. The peaks that elute at 30.9 and 29.6 counts, respectively, were identified as monomer and dimer bisphenol-A bischloroformate. Trimer bisphenol-A bischloroformate elutes at 28.8 counts, but it is not resolved in Figure 2. The broad portion of the elution curve that peaks around 27 counts consists of all oligomers that are three and higher in degree of polymerization. 

When product made with a 2 1 ratio of BPA to sodium hydroxide was extracted with boiling hexane, a 45% yield of monomer bisphenol-A bischloroformate could be isolated from the hexane-soluble fraction. The GPC curves of the product isolated by the boiling-hexane extraction are shown in Figure 4. The GPC curve indicates that a small amount... 

Figure 4. GPC curves of the products separated by the boiling-hexane extraction of bisphenol-A oligomer bischloroformates prepared by the aqueous alkaline technique at mole ratio (NaOH ...

Figure 5. GPC curves of bisphenol-A oligomer bischloroformates prepared in benzene and THF using the same phosgene excess...

Figure 6. GPC curves of bisphenol-A oligomer bischloroformates prepared in benzene and THF. When the phosgene excess is increased from 11 to 50% with benzene as cosolvent, the molecular-weight distribution is relatively unchanged, compared with Figure 5. However, with THF as cosolvent, a change in phosgene excess from 12.5 to 25% causes a marked change in molecular-weight...

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