Marudai Balasubramanian

Aqueous organic chemistry: 5. Diaryl ethers: diphenyl ether, 1-phenoxynaphthalene and 9-phenoxyphenanthrene

Diaryl ether model compounds, representative of thermally stable cross-links in coals, are cleaved under aquathermolysis conditions. 1-Phenoxynaphthalene and 9-phenoxyphenanthrene, although inert to thermolysis in cyclohexane, were reactive under all the aquathermolytic conditions studied. Phenol and 1-naphthol were the major products from 1-phenoxynaphthalene. 9-Phenoxyphenanthrene was more reactive and similarly yielded phenol and 9-hydroxyphenanthrene. In a reducing atmosphere (15% formic acid or 15% sodium formate) the 1-naphthol and 9-hydroxyphenanthrene products undergo slow reductive dehydroxylation. Diphenyl ether was unaffected at 315 °C under both thermolytic and aquathermolytic conditions, except in the presence of 15% aqueous sodium formate or 15% phosphoric acid where phenol was formed. These facile acid-catalysed ether cleavages of 1-phenoxynaphthalene and 9-phenoxyphenanthrene in water at 315 °C, were markedly decreased in the presence of calcium montmorillonite, CaCO3, LiCl, NaCl, KCl, KBr, MgSO4, BaSO4, Na2SO4, and inhibited by Na2CO3. The rate of reaction for cleavage of these diaryl ethers was inversely proportional to the concentration of the salts.

Aqueous organic chemistry. 9. Reactivity of 1,5-, 1,6-, 1,7- and 2,6-dihydroxynaphthalenes, dibenzofuran, 2-hydroxydibenzofuran, carbazole, 2-hydroxycarbazole, acridine and 4-hydroxyacridine

Dihydroxynaphthalenes with the hydroxyl groups on the same or different rings and polycyclic hydroxyaromatics as present in low-rank coals, or generated during coal conversion, undergo hydrogenation via their keto tautomers under aqueous-CO conditions. The hydrogen donor moieties formed can then transfer hydrogen to radicals generated during the process or in a subsequent liquefaction step.

Dramatic effects caused by alkali metal salts on hydrolytic reaction rates of diaryl ethers in aqueous solutions at high temperatures (250 and 315 °C)

Variations in hydrolysis rates indicate that alkali metal halides and sodium sulfate behave as salts of strong bases and weak acids at high temperatures.

Unprecedented pyridine ring CC bond cleavages by formic acid.

Abstract Formic acid at 350°C converts pyridine and 4-methylpyridine into products deriving from both αβ and βγ CC bond cleavages of the pyridine ring.