Aromatic carboxylic

The two-step poly(amic acid) process is the most commonly practiced procedure. In this process, a dianhydride and a diamine react at ambient temperature in a dipolar aprotic solvent such as /V,/V-dimethy1 acetamide [127-19-5] (DMAc) or /V-methy1pyrro1idinone [872-50-4] (NMP) to form apoly(amic acid), which is then cycHzed into the polyimide product. The reaction of pyromeUitic dianhydride [26265-89-4] (PMDA) and 4,4 -oxydiani1ine [101-80-4] (ODA) proceeds rapidly at room temperature to form a viscous solution of poly(amic acid) (5), which is an ortho-carboxylated aromatic polyamide. 

Suitable substrates for the Hunsdiecker reaction are first of all aliphatic carboxylates. Aromatic carboxylates do not react uniformly. Silver benzoates with electron-withdrawing substituents react to the corresponding bromobenzenes, while electron-donating substituents can give rise to formation of products where an aromatic hydrogen is replaced by bromine. For example the silver /)-methoxybenzoate 6 is converted to 3-bromo-4-methoxybenzoic acid 7 in good yield ... 

Sodium or potassium phenoxide can be carboxylated regioselectively in the para position in high yield by treatment with sodium or potassium carbonate and carbon monoxide. Carbon-14 labeling showed that it is the carbonate carbon that appears in the p-hydroxybenzoic acid product. The CO is converted to sodium or potassium formate. Carbon monoxide has also been used to carboxylate aromatic rings with palladium compoimds as catalysts. In addition, a palladium-catalyzed reaction has been used directly to prepare acyl fluorides ArH —> ArCOF. ... 

Carbonyl Carboxyl Aromatic O-Alkyl N-Alkyl Alkyl... 

Hsu, T., Daniel, S. L., Lux, M. F., and Drake, H. L., 1990, Biotransformations of carboxylated aromatic compounds by the acetogen Clostridium thermoaceticum generation of growth-supportive C02 equivalents under C02-limited conditions, J. Bacteriol. 172(1) 2129217. 

From the results in Table 6, the differences between NMR-based and probabilistic model-based estimates of carbonyl -f carboxyl , aromatic , and alkoxy - - alkyl are —8%, —5%, and - -14% for FAs, —11%, —3%, and -K3% for HAs, and —2%, - -1%, and 0% for NOM. The discrepancies observed for most forms of carbon in FAs and HAs are greater than 5%, and they are consistent with theory and observation for CP-MAS NMR spectrometry, in which the ratio of ip -hybridized carbon to ip -hybridized carbon is significantly underestimated (Mao et al., 2000). For NOM, the two approaches yield highly consistent estimates of the distribution of organic carbon. It is perhaps significant that most of the NMR spectra for NOM samples in Figure 7 were obtained on aqueous solutions, not on solid samples, i.e., the CP-MAS method was not used. 

NMR measurements provide insight into the distribution of organic carbon among carbonyl, carboxyl, aromatic, alkoxy, and alkyl stmctural subunits in FAs, HAs, and NOM. All three materials are remarkably similar, and the most probable distribution for all three materials is carbonyl (5%), carboxyl (22%), aromatic (30%), alkoxy (20%), and alkyl (23%). The NMR results are somewhat inconsistent with predictions of the distribution of organic carbon that arise from consideration of elemental composition, carboxyl content, number-average molecular weight, etc. The evidence is clear that carbonyl, carboxyl, and probably aromatic... 

Assignment carboxylate aromatic/ aromatic/ aromatic/ carbonate carbonate... 

Phosphines Containing Carboxylated Aromatic Croups and Side Chains... 

It has been known for some time that certain carboxylic acids inhibit ceruloplasmin 109, 148). Curzon and Speyer 175) examined the inhibitory capacity of a number of types of organic substances including aromatic carboxylates, unsaturated aliphatic carboxylates, aromatic non-carboxylates, unsaturated... 

Tryptophan, phenylalanine, tyrosine Aniline, chloroanlines, methylanilines, chloromethylanilines Nitrophenols, chlorinated phenols, phenolic acids (benzoic, p-hydroxybenzoic, vanillic, caffeic, p-coumaric, ferulic, salicylic, phenazine-1-carboxylic), aromatic anionic surfactants (alkylbenzenesulfonates)... 

Similarly, Venema and Boom-Van Geest [30] have described an in situ hydrolysis/methylation pyrolysis-GC method for the characterisation of polymers. Carboxyl, aromatic amino and hydroxy functional gronps in polymers were methylated in this procednre. 

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