Diphenylmethane, from benzophenone

Further Reduction to a Hydrocarbon. In the reduction of benzo-phenone with aluminum ethoxide the formation of 7% of diphenyl-methane was observed. When benzohydrol was treated with aluminum ethoxide under the same conditions, 28% reduction to diphenylmethane occurred.12 In these reactions acetic acid, rather than acetaldehyde,-was formed from the ethoxide. Aluminum isopropoxide does not give this type of undesirable reaction with this reagent, pure benzohydrol is easily obtained in 100% yield from benzophenone.6 37 However, one case of reduction of a ketone to the hydrocarbon has been observed with aluminum isopropoxide.17 When 9, 9-dimethylanthrone-10 (XU) was reduced in xylene solution, rather than in isopropyl alcohol, to avoid formation of the ether (see p. 190), the hydrocarbon XUII was formed in 65% yield. The reduction in either xylene or isopropyl alcohol was very slow, requiring two days for completion. 

Benzophenone is produced by the oxidation of diphenylmethane (350). This free from chlorine (FCC) route is favored for perfume uses. The Friedel-Crafts reaction of benzene and benzoyl chloride in the presence of aluminum chloride is also possible this reaction may proceed in the absence of catalyst at a temperature of 370°C and pressure of 1.4 MPa (351). 

Diphenylmethane has been prepared with aluminum chloride as a catalyst from methylene chloride and benzene, from chloroform and benzene as a by-product in the preparation of triphenylmethane, and from benzyl chloride and benzene. It has been prepared by the reduction of benzophenone with hydriodic acid and phosphorus, or with sodium and alcohol. It has also been made by heating a solution of benzyl chloride in benzene with zinc dust, or with zinc chloride. The above method is only a slight modification of the original method of Hirst and Cohen. ... 

Varying amounts of diphenylmethane (DPM) are also seen. While the reductive coupling of benzophenone to give TPE was expected, the production of TPA was not. U failed to react with TPE, TPA, or DPM. This indicated that the TPA was formed during the coupling step on the metal surface and not from TPE or DPM. 

Oxidation of diphenylmethane in basic solutions involves a process where rate is limited by and equal to the rate of ionization of diphenylmethane. The diphenylmethide ion is trapped by oxygen more readily than it is protonated in dimethyl sulfoxide-text-butyl alcohol (4 to 1) solutions. Fluorene oxidizes by a process involving rapid and reversible ionization in text-butyl alcohol solutions. However, in the presence of m-trifluoromethylnitrobenzene, which readily accepts one electron from the carbanion, the rate of oxygen absorption can approach the rate of ionization. 9-Fluorenol oxidizes in basic solution by a process that appears to involve dianion or carbanion formation. Benzhydrol under similar conditions oxidizes to benzophenone by a process not involving carbanion or dianion formation. 

Interesting possibilities of synthesis arise when elimination leads to cyclic products. Such cyclization is fairly common with aromatic compounds. The mixture of products obtained from diphenylmethane contains about 25 per cent fluorene 2S> (Table 3). Similarly, benzophenone yields about 30 per cent fluorenone 20). The same method can be applied to the synthesis of heterocyclic compounds. Diphenylamine yields up to 30 per cent carbazol 26 di-phenylether about 10 per cent dibenzofurane 16). 

Benzophenone, as mentioned in the Introduction, has been used to assess the hydrogen donor capacity of coals (11, 12). Unfortunately, most coals react very slowly with this compound at 400°C, equation 1. For example, less than 57o of this ketone is converted to diphenylmethane by a vitrinite-rich sample of Illinois No. 6 coal in benzene in one hour at 400°C. Preliminary work revealed that the exinite, vitrinite, and inertinite isolated from PSOC-828 exhibit small, but apparently significant... 

This procedure is adapted from the method of Schlenk and Bergmann.3 Tetraphenylethylene has been prepared by the reaction of diphenylmethane with diphenyldichloromethane 4 by the reaction of diphenyldichloromethane with silver or zinc 4 by the reaction of thiobenzophenone with copper 6 by the reaction of diphenylmethane with sulfur 6 by the reduction of benzophenone with amalgamated zinc in the presence of hydrochloric acid 7 and by the rearrangement of 1,2,2,2-tetraphenylethanol with acetyl chloride.8... 

Hydrocarbon oxidation. A metal catalyst is usually required. By adding bis(/-riphenylsilyl) chromate," diphenylmethane is oxidized to benzophenone, and vanadium-pillared montmorillonite " catalyzes the conversion of arylacetic esters to arylglyoxylic esters by f-BuOOH. The presence of calcined ZnCrOj-hydrotalcite enables the selective generation of benzylic hydroperoxides from aralkanes."... 

Ar. ketals and thioketals, ar. and aliphatic epoxides, and ar. aziridines can be rapidly and conveniently reduced by alkali metals in liq. NHg. - E A soln. of 5 equivalents Na in liq. NHg added to a soln. of benzophenone ethylene ketal in ether, and the product isolated after 3 hrs. diphenylmethane. Y 94%. F. e., also alcohols from oxido comps., and amines from aziridines, as well as an anomalous aziridine reduction, s. E. M. Kaiser et al., J. Org. Chem. 36, 330 (1971). 

When the UCli is over reduced by using five Li equivalents, the yield of both TPE and TPA is diminished, primarily due to the formation of large amounts of diphenylmethane (DPM). This DPM presumably arises from the action of excess reducing agent on benzophenone in the presence of uranium. 

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