Crystalline carboxylic acids

It is well-known, that in most carboxylic acid crystal structures, the conformation of the carboxyl group is synplanar and that the most frequent and dominant interlink is the syn-syn centrosymmetric dimer synthon, II. This synthon is found in nearly a third of all crystalline carboxylic acids, with or without any other functionality being present in the molecule, signifying robustness.1211 Against such a background, the crystal structures of 1,4-cubane-... 

The simpler examples are readily hydrolysed in aqueous solution, and therefore react with sodium hydrogen carbonate and also give the ester test they may be confirmed by applying the hydroxamic ester test (Section 9.5.3, p. 1222). Carbonyl adsorption is apparent in the infrared spectrum at about 1820 cm-1 and at about 1760cm-1. It should be noted that aromatic anhydrides and higher aliphatic anhydrides are not readily hydrolysed with water and are therefore effectively neutral (Section 9.5.3, p. 1218). The final characterisation of the acid anhydride is achieved by conversion into a crystalline carboxylic acid derivative as for add halides. 

Gaseous and Liquid Propynoic and Acrylic Acids Crystalline Carboxylic Acids... 

The synthesis starts with the routine nitration of available 228 and the base-catalysed reaction of 227 with benzaldehyde to give 229 (226 R=Ph). It is necessary to protect this and benzylation in base gives predominantly the isomer 230 with the longest conjugated system. Ozonolysis (ozonation) reveals the stable crystalline carboxylic acid 232. After deprotection, both isomers give 225. 

The molecular packing characteristics of crystalline carboxylic acids have been analyzed both qualitatively [39, 135, 136] and quantitatively by atom-atom potentials [24, 26, 98). Here we review some of their principal packing characteristics. 

Figure 4 Some hydrogen-bonding patterns in crystalline carboxylic acids. The dimer motif is used in terephthalic acid, trimesic acid and adamantane-l,3,5,7-tetracarboxylic acid to obtain networks of increasing dimensionality...

A white pleasant-smelhng crystalline carboxylic acid, CgH5CH CHCOOH. It occurs in amber but can be synthesized and is used in perfumes and flavorings. 

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