Diphenaldehydic acid

B. Diphenaldehydic acid. A mixture of 10 g. (0.0368 mole) of 3,8-dimethoxy-4,5,6,7-dibenzo-l,2-dioxacyclooctane, 50 ml. of 10% sodium hydroxide solution, and 200 ml. of 95% ethyl alcohol is heated under reflux for 15 minutes, during which time the solid dissolves (Note 3). The solution is cooled, acidified with concentrated hydrochloric acid, and diluted to the cloud point with water. Crystallization is induced by rubbing the side of the vessel with a stirring rod (Note 4). More water is then added slowly until crystallization is complete. Filtration yields 6.7-7.3... 

The method here described is based on the reported ozonolysis of phenanthrene in methanol, followed by conversion of the initial ozonolysis product to diphenaldehyde (p. 41), diphenalde-hydic acid, methyl diphenaldehydate (Note 6), and diphenic acid (Note 7). Diphenaldehydic acid has previously been made in low yields by oxidative decomposition of the monohydrazide of diphenic acid.3-4 The presently described method is far superior, not only in yield, but also in simplicity. 

If sodium hydroxide is omitted in this preparation and the reaction mixture is refluxed until it no longer gives a positive peroxide test with iodide ion (Note 3) (about 2 hours), the product is the methyl ester of diphenaldehydic acid in 91-98% yield (m.p. 50-51°).2... 

Reduction of the eight-membered ring peroxide (137) with potassium iodide in glacial acetic acid leads to an 84% yield of 2,2 -diphenyl-dialdehyde.141 The base-catalyzed decomposition of 137 gives 2,2 -diphenaldehydic acid in 84% yield. Diphenic acid (84%) is obtained when 139 is heated with a mixture of 30% hydrogen peroxide and 10% sodium hydroxide solution.141... 

The breakdown of the benzene ring to aldehydes is extremely rare and has been achieved only by ozone. A historical and classical example is the disintegration of o-xylene to a mixture of glyoxal, methyl glyoxal, and diacetyl (butanedione) in the predicted ratios [104]. From the preparative point of view, the conversion of phenanthrene into 0,0 -diformyl-biphenyl (diphenaldehyde) [1123] or o-formylbiphenyl-o -carboxylic (diphenaldehydic) acid [1124] is more important (equation 154). 

Diphenaldehyde, 41, 41 Diphenaldehydic acid, 41, 46 methyl ester of, 41, 47 Diphenic acid, 41, 47... 

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