Diphenylmethane, formation

If the alkyl halide contains more than one, equally reactive C-halogen centers, these will generally react each with one aromatic substrate molecule. For example dichloromethane reacts with benzene to give diphenylmethane, and chloroform will give triphenylmethane. The reaction of tetrachloromethane with benzene however stops with the formation of triphenyl chloromethane 7 (trityl chloride), because further reaction is sterically hindered ... 

The effect of solvent upon k2 has been reported , and it was concluded that the activated complex is not sufficiently polar to be called ionic . The oxidations of toluene and triphenylmethane exhibit primary kinetic deuterium isotope effects of 2.4 and ca. 4 respectively. No isotopic mixing occurred during formation of the Etard complex from a mixture of normal and deuterated o-nitrotoluene . The chromyl chloride oxidation of a series of substituted diphenylmethanes revealed that electron-withdrawing substituents slow reaction while electronreleasing groups have the opposite effect, the values ofp andp being —2.28 + 0.08 and —2.20 + 0.07 respectively . ... 

Stairs comments that this p value is strongly dependent on the temperature but his data have been criticised by Duffin and Tucker ", who prefer their method of observing the rate of formation of the adduct to that of estimating total residual oxidising power employed by Stairs, and they find p (25°) to be —2.32+0.10 as compared to a value of —2.20+0.07 at 40 °C. These values are considerably more negative than those found for chromic acid oxidation of diphenylmethanes (— 1.17) and toluenes (-1.12). 

The relative rates of oxidation of phenylmethanes cover too small a range to be compatible with carbonium ion formation cf. the discussion on chromic acid oxidation of diphenylmethane, p. 295), and an initial reaction to give a radical plus Cr(V) followed by rapid transfer of a second electron to form Cr(IV) is more... 

The first stage of the reaction is deprotonation of diphenylmethane. This stage is limiting. The formation of benzophenone includes the following stages [284] ... 

As documented by Pedley, only enthalpies of combustion and sublimation have been reported for 6,6-diphenylfulvene. We recommend the measurement of the enthalpy of hydrogenation to form a-cyclopentyl diphenylmethane to acquire a more precise enthalpy of formation. 

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... 

Isocyanates are capable of co-reacting to form dimers, oligomers and polymers. For example, aromatic isocyanates will readily dimerize when heated, although the presence of a substituent ortho to the -NCO group reduces this tendency. For example, toluene diisocyanate (TDI) is less susceptible to dimer formation than diphenylmethane diisocyanate (MDI). The dimerization reaction is reversible, with dissociation being complete above 200 °C. It is unusual for aliphatic isocyanates to form dimers, but they will readily form trimers, as do aromatic isocyanates. The polymerization of aromatic isocyanates is known, but requires the use of metallic sodium in DMF. 

Stance, oxidation of diphenylmethane with 0.1 mol % 5a and 10 equiv. of 30% H2O2 under ambient conditions afforded a 1 1 mixture of diphenylmethanol and benzophenone in 34% yield after 16 h. When heated to 80 °C for 5 h, the reaction is driven to the formation of benzoquinone in 87% yield. Cu(OAc)2 and Cu (salen) also afforded benzoquinone under identical conditions, but were found to be less effective than 5a. 

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. 

Treatment of diphenylmethane in basic solution with a trace of oxygen in DMSO solutions fails to produce significant amounts of a paramagnetic product detectable by ESR spectroscopy. On the other hand, treatment of benzhydrol with traces of oxygen in basic solution can produce significant amounts of the ketyl. Pyridylthiazolylcarbinols are readily converted to the ketyls by base in alcoholic solution. (24). In pure DMSO significant amounts of the ketyl are formed whereas in tert-butyl alcohol or DMSO (80% )-tert-butyl alcohol (20% ) only traces of the ketyl can be detected. These results are consistent with the formation of the ketyl under oxidative conditions by Reaction 31. Only under the most basic conditions (pure DMSO) is the dianion formed by... 

Cyclophanes consist of a class of artificial hosts featured with well-defined hydrophobic cavities constructed by aromatic rings incorporated in their macrocy-clic structures, and also with high design versatility because they are totally synthetic.The first direct evidence of the formation of an inclusion complex with an organic guest was obtained for tetraazacyclophane 62, the cavity of which is constructed with diphenylmethane units bridged by tetramethylene chains. 

To address this concern uretonimine-modified isocyanates with improved low-temperature properties were prepared using 4,4 -diphenylmethane diisocyanate catalyzed with 3-methyl-l-phenyl-3-phospholene-l-oxide. The formation of uretonimine was consistently higher than uretdione formation using this catalyst. The uretonimine-modified isocyanate can be stored at temperatures substantially lower than ambient temperature while still remaining liquid. In addition it is soluble in melted 4,4 -diphenylmethane diisocyanate. 

Kennedy and Stock reported the first use of Oxone for many common oxidation reactions such as formation of benzoic acid from toluene and of benzaldehyde, of ben-zophenone from diphenylmethane, of fratw-cyclohexanediol from cyclohexene, of acetone from 2-propanol, of hydroquinone from phenol, of s-caprolactone from cyclohexanone, of pyrocatechol from salicylaldehyde, of p-dinitrosobenzene from p-phenylenediamine, of phenylacetic acid from 2-phenethylamine, of dodecylsulfonic acid from dodecyl mercaptan, of diphenyl sulfone from diphenyl sulfide, of triphenylphosphine oxide from triphenylphosphine, of iodoxy benzene from iodobenzene, of benzyl chloride from toluene using NaCl and Oxone and bromination of 2-octene using KBr and Oxone126. Thus, they... 

Ultraviolet irradiation of CCXLV, which is obtained by the condensation of diphenylketene and diphenyldiazomethane, in hydroxylic solvents, effects its cleavage into the starting materials in the presence of carboxylic acids or alcohols, photoaddition takes place with the formation of benzilic acid derivatives.167 On the other hand, irradiation of CCXLV in benzene containing acetic acid and/or methanol produces CCXLVI and CCXLVII, respectively. Irradiation in the presence of diphenylmethane under nitrogen atmosphere yields phenylacetic acid. 

In the same study, a one-pot variant avoiding the isolation of the intermediate hydrazone was attempted. However, reduction of the crude hydrazone leads to the formation of by-products for example, in the reaction of benzophenone, a mixture of diphenylmethane and benzophenone azine was found (Scheme 4.38)64. 

The catalysts of reactions between 4,4 -diphenylmethane diisocyanate (MDI) and alcohols in N,N-dimethylformamide (DMF) by dibutylin dilaurate has been investigated. The reaction rate of the catalyzed urethane formation in DMF is proportional to the square root of dibutylin dilaurate concentration. This result differs from that of similar studies on apolar solvents. The catalysis in DMF can be explained very well by a mechanism in which a small amount of the dibutylin dilaurate dissociates into a catalytic active species. 

T n continuation of a study of the uncatalyzed reactions between MDI (4,4 -diphenylmethane diisocyanate) and alcohols in DMF (N,N-dimethylformamide) (J), the effect of dibutyltin dilaurate on the same reactions has been studied. The results were compared with those found in studies on the mechanism of catalysis of urethane formation in apolar solvents (2-6). 

The most likely lignin condensation reaction during the kraft cook is the formation of diphenylmethane structures 29, 30). These structures are also proposed 14) as being already present in native lignin. Phenolic diphenylmethanes do not exhibit any color, but they can easily be dehydrogenated to quinonemethides 20, 23) or quinonemethide radicals (P). 

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