Diphenylmethane mixture

This tri-isocyanate is reported to impart good light stability and weather resistanee in polyurethane eoatings and is probably the most widely used aliphatic isocyanate. A number of other aliphatic polyisocyanates have been introduced recently in attempts to produce polyurethanes with improved light stability. Amine derivatives of diphenylmethane are made by reacting aniline of toluidines with formaldehyde. These can lead to a mixture of di-isoeyanates, the diphenylmethane di-isocyanates (MDIs) of commerce. Triphenylmethane-pp p"-tny tri-isocyanate is produced from leucorosaniline. 

Diphenylmethane.—This reaction is analogous to that of aluminium chloride on a mixture of benzene and ben/yl chlonde refeired to in the notes on Prep. 100, p. 310. The leactiun is also effected by the use of zinc dust or finely-di ided coppei (Zincke). 

As described in U.S. Patent 2,421,714 (a) benzhydryl bromide is first prepared as follows 840 parts by weight of diphenylmethane is heated to 130°C with stirring. In the presence of a 200 watt electric light 6 inches from the flask, 880 parts of bromine is added slowly. Liberation of HBr occurs and addition requires 1 hour and 45 minutes. The temperature is maintained at 130°C for an additional 30 minutes. A fine stream of air is blown in to remove HBr and Brj while the reaction mixture cools. Benzene (180 parts) is added and the solution used immediately in (b) below. 

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 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 . ... 

The apparatus required is similar to that described for Diphenylmethane (Section IV,4). Place a mixture of 200 g. (230 ml.) of dry benzene and 40 g. (26 ml.) of dry chloroform (1) in the flask, and add 35 g. of anhydrous aluminium chloride in portions of about 6 g. at intervals of 5 minutes with constant shaking. The reaction sets in upon the addition of the aluminium chloride and the liquid boils with the evolution of hydrogen chloride. Complete the reaction by refluxing for 30 minutes on a water bath. When cold, pour the contents of the flask very cautiously on to 250 g. of crushed ice and 10 ml. of concentrated hydrochloric acid. Separate the upper benzene layer, dry it with anhydrous calcium chloride or magnesium sulphate, and remove the benzene in a 100 ml. Claisen flask (see Fig. II, 13, 4) at atmospheric pressure. Distil the remaining oil imder reduced pressure use the apparatus shown in Fig. II, 19, 1, and collect the fraction b.p. 190-215°/10 mm. separately. This is crude triphenylmethane and solidifles on cooling. Recrystallise it from about four times its weight of ethyl alcohol (2) the triphenylmethane separates in needles and melts at 92°. The yield is 30 g. 

The practical route for oxidizing leuco diphenylmethanes 15 demands inital conversion to an imine salt 16. The imine salt is obtained by heating a mixture of diphenylmethane, sulfur, ammonium chloride, and sodium chloride at 175°C in a current of ammonia or by heating a mixture of diphenylmethane, urea, sulfamic acid, sulfur, and ammonia at 175°C (Scheme 3). Dyes 16 can be represented as the quinonoid resonance structure 17. Dyes of this class, known as auramines, are all yellow, with the only commercial representative being auramine O 16a. Due to its poor lightfastness and instability to hot acids and bases, its use has been restricted to dyeing and printing cotton, paper, silk, leather, and jute. 

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... 

Materials. Methylene 4,4 -diphenyldiisocyanate (MDI, Mobay) was recrystallized from cyclohexane. Toluenediisocyanate (TDI— represents mixture of 2,4- and 2,6-isomers in 80/20 ratio), p-toluidine (Aldrich) and aniline (Aldrich) were purified by vacuum distillation before use. Diphenylmethane, tert-butyl peroxide (TBP), 4-bromoaniline, butyl lithium in hexane, and ethyl chloroformate, were obtained from Aldrich and used as received. Spectrograde tetrahydrofuran (THF) and benzene from Burdick and Jackson were used as received. Poly(tetramethylene ether glycol) with MW 1000 was obtained from polysciences and dehydrated under a rough vacuum at 50 °C for 24 h. 

The results of an experiment for the laser flash photolysis (Xex=351 nm) of a 6.0 X 10 M solution of diphenylmethane in a 60/40 mixture of TBP and benzene (Figure 6) shows a distinct absorbance peak maximum at 340 nm characteristic of the unsubstituted diphenylmethyl radical. The results in Figure 6 illustrate the utility of TBP in indirect generation of diphenylmethyl radicals. 

A key factor in the preparation of polyurethanes is the reactivity of the isocyanates. Aromatic diisocyanates are more reactive than aliphatic diisocyanates, and primary isocyanates react faster than secondary or tertiary isocyanates. The most important and commercially most readily accessible diisocyanates are aliphatic and colorless hexamethylene-1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI),and aromatic, brownish colored diphenylmethane-4,4 -diiso-cyanate (MDI), 1,5-naphthalenediisocyanate, and a 4 1 mixture of 2,4- and 2,6-toluenediisocyanates (TDI). 

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. 

Polyurethanes (PU s). SL and 4,4 -diphenylmethane diisocyanate (MDI) were dissolved in tetrahydrofuran (THF), and the solution was stirred for 1 hr at 60°C. A THF solution of polyethylene glycol (PEG 400) and diethyl bis(2-hydroxyethyl)aminomethylphosphonate (polyol containing phosphorous) was added to the reaction mixture, and the reaction time was extended for 1 hr. In all reactions, the molar ratio of the total amount of isocyanate groups to the total amount of hydroxyl groups (NCO/OH) was maintained at 1.2. The lignin content in PU was 20 wt%. Each solution was drawn on a glass plate, and allowed to dry for 48 hr. The residual solvent in a sample was removed under vacuum and curing of each PU film was carried out at 120°C for 3 hr under a pressure of 50 kg/cm2. 

A reactor was charged with 93.80% 4,4 -diphenylmethane diisocyanate, 6.20% 2,4 -diphenylmethane diisocyanate, and 3-methyl-1 -phenyl-3-phospholene-1 -oxide (6 ppm) as catalyst and then heated for 6 hours at 110°C. Trifluoromethanesulfonic acid (50 ppm) was then added to quench the reaction. The mixture was then cooled to 50°C and the product isolated having a 29.5% isocyanate content. 

Because r is larger than r then a linear plot ofln k vs. 1 /eR with a positive slope will be obtained irrespective of the charge on the ion. The observation3 that a positive slope of log/c vs. l/sR was obtained for the oxidation of triphenylmethane and diphenylmethane by [Fe(CN)6]3 in various mixtures of aqueous acetic acid was taken as proof that the rate determining step was of the ion dipole type, i.e. involved [Fe(CN)6]3- and the arylalkane molecule. 

With shorter periods of standing and lower temperatures, the yield falls off materially. Thus in one experiment in which the mixture was allowed to stand for twenty-four hours at 5-8°, a large proportion of a lower-boiling product (apparently diphenylmethane) was formed, and only 109 g. of crude tri-phenylmethane was obtained. 

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. 

Pearl and Dickey (20) isolated 3,3 -dimethoxy-4,4 -dihydroxybenzo-phenone, an analog of the diphenylmethanes apparently present in our product mixture. They suggest that the ketone is a rearrangement product of vanillil. In our system the corresponding diphenylmethanes could also be produced by a coupling reaction of phenolic methylols or quinonemethides, and at present they cannot be considered proved structural elements native to lignin. 

A mixture of benzophenone (1.84 g, 10 mmol) and 80% hydrazine hydrate (1 g, 20 mmol) in toluene (15 mL) was taken in an Erlenmeyer flask and placed in a commercial microwave oven operating at 2450 MHz frequency. After irradiation of the mixture for 20 min, (monitored by TLC) it was cooled to room temperature, extracted with chloroform and dried over anhydrous Na2S04. Removal of solvent gave the benzophenone hydrazone in 95% yield. For the Wolff-Kishner reductions, a mixture of hydrazone 3a (5 mmol) and KOH (2 g) were taken in an Erlenmeyer flask and placed in a microwave oven. Irradiation for 30 min and usual workup gave the corresponding diphenylmethane in 95% yield. 

---