Amide-ester interchange reaction

Hydrolysis of Copolyamide-esters (CPAEs) by Lipase (jj,). CPAEs were synthesized by the amide-ester interchange reaction between polyamide and polyester. The length of the polyamide blocks was measured after hydrolysis of ester bonds in CPAE by alkali at 30 C. The infrared spectra after hydrolyzing ester bonds on CPAEs showed that the ester bonds were almost completely removed. The molecular weight distribution of polyamide blocks was examined by GPC (Table II). The following samples were used CPAE-1 (reaction time for synthesis, 1 hr) and CPAE-2 (reaction time, U hr) composed of nylon 6 and PCL at a 50/50 molar ratio, CPAE-3 (reaction time, 1 hr) and CPAE-U (reaction time,... 

PEAs were firstly obtained in 1979 from polyamides and polyesters by temperature-induced amide-ester interchange reactions. Since then, a considerable body of literature has been developed due to the noticeable characteristics and properties of the new polymers. For more detailed information on the synthesis and applications of... 

Presumably, the alkoxide ion formed in this reaction can react with the lactam to recreate the activated monomer. However, this reaction may be quite slow compared to the polymerization reaction. Similarly in the cationic polymerization, imide fomation probably occurs by an acid-catalyzed amide-ester interchange reaction to yield benzyl alcohol. In both cases, very little is known about the effects of these byproducts on the polymerization reaction. 

The dimethyl ester of a carboxy-terminated diamide is reacted with 1,2-ethanediol in the conditions of PBT synthesis. The amide functions are unaffected while the hydroxy-ester interchange reaction proceeds to the formation of an alternating copolyesteramide (Scheme 2.60). The procedures given below are reproduced from ref. 430. (Copyright 1997 Elsevier Science Ltd, with permission of the copyright owner.)... 

Estane VC products, 201 Ester-amide copolymers, 146, 147 Esterases, 82 Esterification, direct, 63 Ester interchange catalysts, 71 Ester interchange reactions, 31, 62-63,... 

Benzene and thiophene rings can of course often be interchanged in biologically active agents. The very broad structural latitude consistent with NSAID activity is by now a familiar theme as well. Preparation of the fused thiophene counterpart of the NSAID piroxicam (Chapter 11) starts with the reaction of thiophene (25-1), itself the product of a multistep sequence, with ethyl A-methylglycinate to give the sulfonamide (25-2). Treatment of that intermediate with a base leads to intramolecular Claisen condensation and thus the formation of the 3-ketoester (25-3). An amide-ester interchange with 2-aminopyridme (25-4) completes the synthesis of tenoxicam (25-5) [25]. 

An ester interchange reaction occurring when ester is heated in the presence of hydroxy compound (alcoholysis) or acid compound (acidolysis). Since esterification is reversible, the transesterification occurs between mixed esters in the presence of (thermally activated) low concentration of volatile reaction by-products. Ester-amide exchange can also be accomplished by similar (catalyzed) process. 

Certain alkyd resins can be combined with modified polyamide resins to produce materials exhibiting a marked degree of true thixotropy when dissolved in suitable solvents. This valuable property is maintained when such products are used in the manufacture of paints. When the alkyd and polyamide are heated at elevated temperature, amide and ester interchange reactions occur that split the polyamide chains and affix the fragments to the alkyd molecule. In further reactions, the amide groups are scattered throughout the molecule. The reactions probably proceed in the following way ... 

By the chemical reaction used to produce new bonds vinyl addition, esterification, amidation, ester interchange, and so on... 

Esters are most commonly prepared by the reaction of a carboxyHc acid and an alcohol with the elimination of water. Esters are also formed by a number of other reactions utilizing acid anhydrides, acid chlorides, amides, nitriles, unsaturated hydrocarbons, ethers, aldehydes, ketones, alcohols, and esters (via ester interchange). Detailed reviews of esterification are given in References 1—9. 

Figure 6.3 Classical condensation reaction are (A) esterification, (B) ester interchange, (C) amidization, and (D) intramolecular reaction. Two routes, A and B, can be taken to prepare PET. (From Fried, J.R., P a. Eng., 38(10), 27, 1982. With permission.)...

There are a number of ways that a stepwise reaction can take place. These include direct reaction, interchange, and add chloride/anhydride. Direct reactions include formation of polyesters and polyamides. Typical interchange reactions involve acetol-alcohol, amine-amide, and amine-ester. The last-named are cases in which an anhydride or acid chloride are reacted with a glycol or amine. 

Another type of adventitious block polymer formation occurs in the partial inter-randomization in the melt of mixtures of homopolymers such as polyesters and polyamides which can undergo ester-ester, amide-amide or ester-amide interchange reactions. 

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