Diphenylmethane production

One solution to the aforementioned problem, realized by Tundo and co-workers, involved the addition of quaternary ammonium salts to the typical Blanc reaction mixture. For example, addition of hexadecyltri-methylammonium bromide to normal Blanc reaction conditions with cumene results in a two-phase system, where the reaction proceeds with high conversion ( 89%) and high selectivity for formation of the mono-chloromethyl derivative (99%). Under these conditions, virtually none of the diphenylmethane product is observed. 

By-products are formed in both preparations thus in the former, anthracene, and o- and p-dibenzylbenzenes are present in the fraction of high boiling point. Diphenylmethane is more conveniently obtained by the interaction of benzyl chloride and benzene in the presence of aluminium amalgam ... 

Monochlorobenzene. The largest use of monochlorobenzene in the United States is in the production of nitrochlorobenzenes, both ortho and para, which are separated and used as intermediates for mbber chemicals, antioxidants (qv), dye and pigment intermediates, agriculture products, and pharmaceuticals (Table 5). Since the mid-1980s, there have been substantial exports of both o-nitrochlorobenzene, estimated at 7.7 million kg to Europe and -nitrochlorobenzene, estimated at 9.5 million kg to the Far East. Solvent use of monochlorobenzene accounted for about 28% of the U.S. consumption. This appHcation involves solvents for herbicide production and the solvent for diphenylmethane diisocyanate manufacture and other chemical intermediates. 

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. ... 

Formulations for one-shot polyether systems are similar to those used for flexible foams and contain polyether, isocyanate, catalyst, surfactant and water. Trichloroethyl phosphate is also often used as a flame retardant. As with polyesters, diphenylmethane di-isocyanate is usually preferred to TDI because of its lower volatility. Tertiary amines and organo-tin catalysts are used as with the flexible foams but not necessarily in combination. Silicone oil surfactants are again found to be good foam stabilisers. Volatile liquids such as trichlorofluoro-methane have been widely used as supplementary blowing agents and give products of low density and of very low thermal conductivity. 

Adhesives based on isocyanate (especially PMDl, polymethylene diisocyanate, more exactly polymeric 4,4 -diphenylmethane diisocyanate) have been used for more than 25 years in the wood-based panel industry [88], but still have a low market value in the wood-working industry compared to systems based on UF-, MUF- or PF-resins. The main application is the production of waterproof panels, but also the production of panels from raw materials that are difficult to glue, like straw, bagasse, rice shells or sugar cane bagasse. They can be used as adhesives for wood-based products like particleboard, oriented strandboard (OSB), laminated strand lumber (LSL), medium-density fiberboard (MDF) or... 

The conductometric results of Meerwein et al. (1957 b) mentioned above demonstrate that, in contrast to other products of the coupling of nucleophiles to arenediazonium ions, the diazosulfones are characterized by a relatively weak and polarized covalent bond between the p-nitrogen and the nucleophilic atom of the nucleophile. This also becomes evident in the ambidentate solvent effects found in the thermal decomposition of methyl benzenediazosulfone by Kice and Gabrielson (1970). In apolar solvents such as benzene or diphenylmethane, they were able to isolate decomposition products arising via a mechanism involving homolytic dissociation of the N — S bond. In a polar, aprotic solvent (acetonitrile), however, the primary product was acetanilide. The latter is thought to arise via an initial hetero-lytic dissociation and reaction of the diazonium ion with the solvent (Scheme 6-11). 

The Michael addition of nucleophiles to a,/J-unsaturated sulfoxides creates initially a-sulfmyl carbanions by nucleophilic attack on the /J-carbon atom. Russell and Becker157 found that treatment of a mixture of diphenylmethane and anisaldehyde with potassium t-butoxide in DMSO gave at first the condensation product 170, which upon Michael addition afforded the final product 171. 

The main products of diphenylmethane (DPM) cracking were benzene and toluene. Very small amounts of polymerized by-products have been found (< 0.5%), but no cyclohexane or partially hydrogenated compounds like cyclohexylphenylmethane were detected. 

Triphenylmethane leuco dyes are far more important than the diphenylmethanes in terms of practical value. Use of triphenylmethane dyes for traditional applications of dyes is limited to dyeing wool, silk, leather, and polyacrylonitrile fibers. The largest portion of the annual production of this class of leuco dyes is consumed in the manufacturing of various copying papers. 

During the hydrogenation of benzophenone to benzhydrol, the undesired side-product, diphenylmethane, is obtained by hydrogenolysis of the C-O bond (Scheme 4.25). 

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. 

It can be seen that primary and secondary R02 radicals disproportionate with the participation of the a-C—H bond. This explains why the substitution of D in the a-position for H retards the recombination of R02 [/tn//tD =1.9 for ethylbenzene, h/ d = 2.1 for styrene, and h/ d=1-37 for diphenylmethane [179]). Because of this, R02 radicals of unsaturated compounds with a double bond in the a-position to the peroxyl free valence disproportionate more rapidly than structurally analogous aliphatic peroxyl radicals (at 300 K, 2kt = 2x 107 and 3.8 x 106 L mol-1 s-1 for R02 radicals of cyclohexene and cyclohexane, respectively [180]). Among the products of secondary peroxyl radicals disproportionation, carbonyl compound and alcohol were found in a ratio of 1 1 at room temperature (in experiments with ethylbenzene [181], tetralin [103], and cyclohexane [182-184],... 

Diphenylmethane reacts with dioxygen in the presence of potassium 1,1-dimethylethoxide in various solvents (dimethylformamide [DMF], hexamethylphosphoramide [HMPA], pyridine) to produce nearly 100% yields of benzophenone [284]. The adduct of benzophenone with dimethylsulfoxide (DMSO) [l,l-diphenyl-2-(methylsulfinyl)ethanol] is formed as the final product of the reaction. The stoichiometry of the reaction and the initial rate depends on the solvent (conditions 300 K, [Ph2CH2] = 0.1mol L [Me3COK] = 0.2mol L 1,p02 = 97kPa). 

In order to rationalize the complex reaction mixtures in these slurry reactions the authors suggested that irradiations of the oxygen CT complexes resulted in simultaneous formation of an epoxide and dioxetane36 (Fig. 34). The epoxide products were isolated only when pyridine was co-included in the zeolite during the reaction. Collapse of the 1,1-diarylethylene radical cation superoxide ion pair provides a reasonable explanation for the formation of the dioxetane, however, epoxide formation is more difficult to rationalize. However, we do point out that photochemical formation of oxygen atoms has previously been observed in other systems.141 All the other products were formed either thermally or photochemically from these two primary photoproducts (Fig. 34). The thermal (acid catalyzed) formation of 1,1-diphenylacetaldehyde from the epoxide during photooxygenation of 30 (Fig. 34) was independently verified by addition of an authentic sample of the epoxide to NaY. The formation of diphenylmethane in the reaction of 30 but not 31 is also consistent with the well-established facile (at 254 nm but not 366 or 420 nm) Norrish Type I... 

Methyl substituted diphenylmethanes are present in trace amounts in the reaction product with ZSM-5 catalyst, and in larger quantities with ZSM-4 catalyst. 

Moro-Oka et al. (1976) have reported that the oxidation of 9,10-dihydroanthracene by K02 solubilized in DMSO by 18-crown-6 gives mainly the dehydrogenated product, anthracene. Under the same conditions, 1,4-hexadiene is dehydrogenated to benzene. The authors proposed a mechanism in which the superoxide ion acts as a hydrogen-abstracting agent only. The oxidations of anthrone (to anthraquinone), fluorene (to fluorenone), xanthene (to xanthone) and diphenylmethane (to benzophenone) are also initiated by hydrogen abstraction. 

All solvents for these solution thermolysis reactions were freshly distilled and all reactions were done in sealed glass tubes heated in a thermostatted oven. Over a wide range of solvents (DMF, naphthalene, diphenylmethane, benzene, toluene, and decalin) there was no significant variation in either isomerization rate or product composition. Reactions were done at 125°C, 155°C and 195°C and the only limitation was that DMF could not be used as the solvent in reactions at 195°C it led to substantial substrate destruction (polymer forming reactions of substrate with DMF ). Isomer compositions were ascertained both by HPLC and by NMR. 

---