Scavengers hydrogen chloride

A variety of metal salts and oxides have traditionally been used to neutralise hydrogen chloride formed in PVC during processing (page 52). The reaction can be represented generally as  

The primary mechanism is HCl scavenging, but the tin chloride and the thiol formed from it are hydroperoxide decomposers similar to DLTP described above. However, the liberated thiol can also add to monoenic unsaturation, thus removing reactive allylic groups from the polymer. 

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A successful procedure for the formation of 2,5-di-t-butylfuran involves reaction of the parent heterocycle with f-butyl chloride in the presence of iron(III) chloride and iron(III) oxide. Iron(III) oxide acts as a hydrogen chloride scavenger and at the same time regenerates the catalyst. Concurrent polymerization normally deactivates the catalyst (82CI(L)603). 

The phosphitylation proceeded in the presence of a catalytic amount of 4-(dimethylamino)pyridine as a nucleophilic [65] activator and-iV AT-diiso-propylethylamine as hydrogen chloride scavenger (step d). The desired phosphoro-amidite was prepared in almost quantitative yield. 

When diaryl tellurium dichlorides and equimolar amounts of ketoximes were stirred for 3 h at 20° in benzene in the presence of triethylamine as hydrogen-chloride scavenger, diaryl tellurium ketoximate chlorides were obtained as white solids2. 

The reaction of N,N -dialkylureas 43 with p-toluenesulfonyl chloride in the presence of pyridine as hydrogen chloride scavenger and solvent gives carbodiimides 44. In this manner... 

The amino group in 2-aminophenyl ethyl tellurium was acylated by various acid chlorides in a dichloromethane medium at 0 with triethylamine serving as hydrogen chloride scavenger. ... 

Use Stabilizing and rust-inhibiting agent for silicones, lubricant and fuel additive, polymerization catalyst, hydrogen chloride scavenger. 

Among the tertiary amines examined, pyridine has proved to be most effective in the polycondensation reaction, and the most favorable results have been obtained in pyridine, suggesting that this solvent is not only a simple hydrogen chloride scavenger but also involved in the reaction itself. 

The required novel bifunctional monomers are synthesized by reacting cyclic ureas with aliphatic or aromatic dicarboxylic acid chlorides in the presence of triethylamine as hydrogen chloride scavenger. This reaction is best conducted in an inert organic solvent using an excess of the cyclic urea to prevent polymer formation (Scheme I). 

Polycarbonates are characterized by the carbonate (-0-COO-) interunit linkage. They may be prepared by interfacial polycondensation of bisphenol A and phosgene in methylene chloride-water mixture. The resulting hydrogen chloride is removed with sodium hydroxide or, in the case of solution polymerization, pyridine is used as the hydrogen chloride scavenger. Polycarbonate may also be made by ester interchange between bisphenol A and diphenyl carbonate. 

The thiolate ion can be generated by using an equivalent amount of a tertiary amine, the base serving also as hydrogen chloride scavenger From the intermediate XCIX and primary or secondary amines the corresponding S,N-acetals are obtained ( ). 

A similar procedure can be used for almost any primary or secondary amine and the yields are normally high. In the case of the sensitive aziridine derivatives a loss in yield is encountered due to polymerization. Of course, the amines can be used in excess as both reagents and hydrogen chloride scavengers (for example, see Reference ). 

Derkach and Liptuga ( ) demonstrated the stepwise mechanism leading to carbodiimides by treating phosphorylcarbonimidoyl dichloride (CXI) with a deficient amount of arylamines, such as aniline and p-bromo-aniline. The elimination of hydrogen chloride from the intermediate CXII occurs in diethylether at room temperature, using triethylamine as the hydrogen chloride scavenger. 

In the reaction of N-substituted carboxylic acid amides with phosphorus pentachloride generally the corresponding free imidoyl chlorides (I) or their hydrochlorides (II) (iminium chlorides) are formed. If the iminium chlorides are obtained initially, dehydrochlorination can be achieved by simply heating or using a stronger base, such as triethylamine, as the hydrogen chloride scavenger. 

Polycarbonates are synthesized by interfacial polycondensation of bisphenol A and phosgene. The reaction is conducted in methylene chloride/water, and sodium hydroxide is used as a hydrogen chloride scavenger. Polycarbonates can also be synthesized by means of solution polymerization, using pyridine as the... 

The aliphatic-aromatic isocyanate dimer 5 is obtained in the cyclization of the corresponding allophanoyl chloride in the presence of pyridine as the hydrogen chloride scavenger. Allophanoyl chlorides are readily obtained from aliphatic or aliphatic/aromatic ureas and phosgene. ... 

It is not necessary to use ketenes themselves in the cycloaddition reaction with enamines. Opitz and coworkers have demonstrated that the adducts can be obtained in good yield from carboxylic acid chlorides and enamines in the presence of a tertiary amine as the hydrogen chloride scavenger . 

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