Mellite structure

Under similar conditions fluorene gives mellitic acid in a yield of about 45%, while hexaethylbenzene yields almost exclusively carbon dioxide, without mellitic acid. The experiments outlined above point to the existence of condensed aromatic rings in charcoal. This structure of charcoal has been definitely proved by infra-red... 

Fig.25 Representations of parts of the solid state structure of the salt [TTF+]2[C6(COO)6 H42-]. (i) The hydrogen bonds between the mellitate ions, (ii) The helically arranged TTF cation radicals in the double helix of mellitate anions, (iii) Disorder in the stacks, (a) shows the regular helix, (b) and (c) two dimer faults and (d) the average column with disorder in the A site. Adapted and reprinted with the permission of the Royal Society of Chemistry [191]...

Burdon542 has surveyed the current hypotheses for the structure of humic substances and has concluded that the various products from chemical degradations and NMR data are all consistent with their being mixtures of plant and microbial materials and their microbial degradation products. The examination of soil carbohydrates, proteins, lipids, and aromatics supported this view the presence of colour, fluorescence, ESR signals, mellitic acid, and other features do not contradict it. Regarding the Maillard reaction, some free monosaccharides and the necessary amino species are present in soil, so it may proceed, but only to a small extent it is not a major process. However, in marine environments, the relative abundance of carbohydrates and proteins makes them more probable precursors of humic substances than lignin or polyphenols. 

The objective of a mechanistic study is to identify all contributory steps that are involved in the transformation of the reactants into products. There are difficulties of investigating behaviour in the highly localized laminar zones (reaction interfaces) within which the major activity is located. Identifications of rate limiting steps in carboxylate reactions have usually been based upon comparisons between related salts. Many factors must be considered and little is known of the character of bonding (i.e. covalent or ionic) in the anhydrous reactant structures. Acheson and Galwey [108] concluded that the activation step in the decompositions of oxalates and mellitates involved the rupture of the bond between the cation and anionic oxygen (see Figure 16.2.). 

The structures indicate that 1,3,5-benzenetricarboxylic acid has 3 acid hydrogens, whereas mellitic acid possesses 6 acid hydrogens. Therefore, the neutralization equivalents... 

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