Bisphenol-A bischloroformate

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... 

Other cyclic monomers have been prepared and polymerized through fast ROP. The main focus has been first on bisphenol A carbonate oligocyclic monomers (Brunelle et al., 1994). The oligocyclic monomers were prepared using an amine-catalyzed reaction of bisphenol A bischloroformate, via an interfacial hydrolysis/condensation reaction that also produces linear oligomers and polymers, depending on the structure and concentration of the tertiary amine (Aquino et al., 1994, Table 2.28). 

In 1962, Schnell and Bottenbruch reported the preparation of the cyclic tetrameric carbonate of bisphenol A. Reaction of bisphenol A with an equimolar quantity of bisphenol A bischloroformate in the presence of excess pyridine in a high dilution reaction carried out at 0.05 M concentration led to yields of cyclic tetramer as high as 21% (Equation 8). A variety of bisphenols were similarly converted to their cyclic tetramers. Polymerization at the melting point was also reported. A few years later, Prochaska and then Moody reported preparations of the cyclic trimer of bisphenol A, using similar high dilution techniques. ... 

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. 

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...

Figure 7. GPC curves for the benzene-soluble and insoluble bisphenol-A oligomer bischloroformates prepared using benzene as...

Narrow-distribution bisphenol-A oligomer bischloroformates can be isolated by fractional precipitation of pyridine-prepared oligomers. Oligomer XII was separated into three fractions by adding hexane to a... 

Figure 8. GPC curves of the bisphenol-A oligomer bischloroformates prepared using a 25% excess of phosgene in THF as cosolvent, and fractionated by precipitating from methylene chloride solution by addition of n-hexane. The volume ratios of solvent and nonsolvent are noted...

When the polycarbonate of bisphenol A was made interfacially in a non-solvent for the polymer the distribution of molecular weights showed two clear maxima and was unusually broad [40]. This was probably a consequence of the two-step process often employed in the preparation of polycarbonates here, the first step yields low-molecular-weight polymer from phosgene and the aqueous alkaline solution of the aromatic diol, then an accelerator salt and more alkali and phosgene are added in the second step. Polycarbonates prepared in the melt and in solution show the expected essentially statistical distribution of molecular weights [40]. Polycarbonates have also been prepared from bisphenols and bisphenol bischloroformates studies of this reaction in nitrobenzene solution have shown it to be second order [79]. 

It has been recognized for decades that medium or large sized rings can only be prepared by the so-called "high dilution" technique. Macrocycles of cyclic bisphenol A-carbonates can now be prepared from bischloroformates by manipulating reaction conditions. The reaction can be run at 20%, 30% and even higher concentrations with yields as high as 90% of cyclic material. These macrocycles can be readily... 

The cyclic aromatic oligocarbonates have been separated from the polymers and characterized by several groups. First attempts to synthesize cyclic BPA oligocarbonates were performed using classical high-dilution techniques. For example, Schnell and Bottenbruch reported that the cyclic tetrameric carbonate (5, n = 3, Scheme 13) of BPA could be formed in about 21% yield via slow addition of equimolar amounts of bisphenol and its bischloroformate to pyridine in dichloromethane at a final monomer concentration of 0.05 M. 

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