Carboxylic acid and coal structure

COAL 21 Identify the structural formulas of the functional groups that distinguish carboxylic acids and esters. 

There is ample evidence in the literature for conversion of reactive hydrocarbons to carbonyl compounds by autoxidation. In coals, the final products of autoxidation under the conditions used in the present study could be a mixture of carbonyl and carboxylic acid surface groups. Under mild oxidation conditions, a different set of functional groups such as ethers as proposed by Liotta et al. or epoxides as suggested in Scheme V could be formed. There are numerous examples of alkoxy radicals rearranging to epoxides . Choi and Stock have shown that ethers can be produced from benzhydrol structures, which are invoked as intermediates in Scheme IV. At higher temperatures, the epoxides and ethers are unstable and may rearrange to carbonyl compounds. 

COAL 8 On the basis of structure and the geometry of the identifying group, distinguish among alcohols, ethers, and carboxylic acids. 

Concepts of the compositions of coals influenced many in considerations of the structures of soil HS. For example, the proposal of Fuchs (1931) for structures of coal HAs (Figure 1.1) influenced soil humic scientists. The proposed structure is composed of heterocyclic aliphatic functionalities, some phenol-derived units, and considerable amounts of carboxylic and hydroxyl acidic functionalities. It may be possible that such structures could arise under conditions of elevated temperature and pressure, with oxidation taking place subsequently. Whereas such conditions might prevail during the synthesis of coals, they would be most unlikely to take place during the transformations of organic materials in the soil environment. 

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