Carboxylic acid side groups

Relatively small amounts of acrylic acid can be used in the monomer polymerization mix to give carboxylated nitrile rubber (X-NBR), whose polymer chains have carboxylic-acid side groups. 

Figure 5 (a and b) Chemical structure of the sodium salt of several bile acids 1 cholic acid, 2 chenodeoxycholate, 3 deoxychoUc acid, 4 glycocholic acid, 5 taurochoUc acid, and 6 tauro deoxychoUc acid, (c) Structures of micelles from choUc acid derivatives, proposed by Small and coworkers. Two or four molecules assemble because of hydrophobic interactions between the cholesterol groups. The hydroxyl groups (black dots on cholesterol) and the carboxylic acids side group shield the hydrophobic domain from water. (Refs. 22-24 for cmcs and Ref. 16 for aggregation numbers.) (Reproduced with permission from Ref. 21. Indian Academy of Sciences, 2004.)... 

High DLs up to 450 wt% were obtained depending on the pyridine content of the polymers. Moreover, the presence of the carboxylic acid side groups did not decrease the doping ability of these copolymers. On the contrary the presence of the carboxylic acid functionalities led to higher DLs compared to the benchmark Copolymer I. High Tg and storage modules E values were obtained for most of the Copolymers XII but most importantly exposure... 

Although these carboxylic acid copolymers are potential candidates for HT-PEMFCs, their most prominent feature was their use for further chemical cross-linking of the carboxylic acid side groups using different cross-linkers creating... 

As a first approach, copol5miers and terpolymers combining main chain pyridine units, cross-linkable carboxylic acid side groups, and/or hydrophobic methyl groups were cross-linked [27]. The carboxylic acid groups can lead to thermally and chemically stable bond formation, as, for example, the creation of imidazole or oxadiazole rings. Thus, in our approach we... 

Several studies have dealt with the problem of discriminating between mastic and dammar, and three marker compounds of mastic have been identified moronic, masticadienonic and acetyl masticadienolic acids [42], The chemical structure of (iso)masticadienonic acid and 3-0-acetyl-3-epi(iso)masticadienonic acid is characterized by a side chain, as for dammarane molecules, but with a carboxylic acid end group (Table 12.1). Under pyrolysis conditions this side chain is susceptible to cleavage as demonstrated by the presence, among the pyrolysis products of mastic, of 2-methyl-pent-2,4-dienoic acid, that perfectly matches with the chemical structure of the side chain end. In addition 3-(9-acetyl-3-epi-(iso)masticadienolic acid also loses the acetyl group and, in contrast to masticadienonic acid, is not detected at all. 

There is only a small selection of nonprotein amino acids that contain carbonyl groups in the form of ketone, aldehyde, and carboxylic acid moieties, as part of the side chain. The examples given in Table 6 are components of nonribosomal peptides isolated from bacteria or fungi and siderophores from bacteria. The biosynthesis of these amino acids is not clear however, some of the amino acids with carboxylic acid side chains may be traced back to the L-a-amino acids aspartic acid and glutamic acid. 

Cleavage of the silyl protecting groups under acidic conditions, followed by exposure to MeS03H. results in ketalization of 26 to the pyran-lactol 27 (Figure 8) [20]. To complete the synthesis of the CP compounds, the primary alcohol has to be oxidized to the carboxylic acid and the carboxylic acid side chain has to be elongated by means of an Arndt-Eistert reaction. 

Teomim et al. [406] reported the synthesis of ricinoleic acid and hydrogenated ricinoleic acid (hydroxystearic acid)-based monomers, which were synthesized from the attachment of a carboxylic acid side chain via a hydrolyzable ester bond to the hydroxy group (succinic acid/maleic acid). These monomers were... 

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