Dimethylaniline processes

In the presence of sulfuric acid, aniline reacts with methanol to form /V-methyl- and /V,/V-dimethylaniline. This is a two-step process... 

Methyl-l-phenyl-3-pyrazolin-5-one gives a green-black dye (736) with 4-nitroso- or 4-amino-dimethylaniline and silver chlorides in the presence of light, a process of great importance in colour photography (B-76MI40403). 

The mechanism proposed for the production of radicals from the N,N-dimethylaniline/BPO couple179,1 involves reaction of the aniline with BPO by a Sn-2 mechanism to produce an intermediate (44). This thermally decomposes to benzoyloxy radicals and an amine radical cation (46) both of which might, in principle, initiate polymerization (Scheme 3.29). Pryor and Hendrikson181 were able to distinguish this mechanism from a process involving single electron transfer through a study of the kinetic isotope effect. 

Tetryl. In the manufacture of Tetryl, it is usual not to nitrate dime thy laniline directly, but to dissolve it first in coned sulfuric acid and then to nitrate the dimethylaniline sulfate so obtained. Direct nitration of dimethylaniline proceeds so violently that it can be carried out only under specialized conditions. Many years experience of Tetryl manufacture has shown that the ratio of sulfuric acid to dimethylaniline should not be lower than 3 1, since a smaller amount of sulfuric acid may be detrimental to the nitration process. However, the ratio of sulfuric acid to dimethylaniline must not be too high, otherwise Tetryl yield is decreased. Temp must be maintained between 20-45° to avoid sulfonation of the benzene ring. Care must be exercised not to leave any unreacted dimethylaniline prior to introduction of nitric acid, because of the potential violence of the dimethyl-aniline-nitric acid reaction. Consequently, continuous methods of prepn are to be preferred as they inherently minimize accumulation of unreacted dimethylaniline... 

Because of the high cost and hygroscopic nature of trifluoroacetic anhydride, a new process, based on dimethylaniline and acrylyl chloride, was considered. Yields averaged 46% and product purities averaged 93.5% (Refs 2, 3 4) ... 

ASARCO [American Smelting and Refining Company] This large metallurgical company has given its name to a flue-gas desulfurization process in which the sulfur dioxide is absorbed in dimethylaniline and subsequently desorbed at a higher temperature. Operated in California, Tennessee, and Norway. 

Methyl red was first prepared 1 by diazotization of anthranilic acid in alcoholic solution, the product being allowed to react with dimethylaniline in the same solvent. It has been stated 2 that this process does not work satisfactorily and yields a different product, of brownish-red color. 

An interesting question then arises as to why the dynamics of proton transfer for the benzophenone-i V, /V-dimethylaniline contact radical IP falls within the nonadiabatic regime while that for the napthol photoacids-carboxylic base pairs in water falls in the adiabatic regime given that both systems are intermolecular. For the benzophenone-A, A-dimethylaniline contact radical IP, the presumed structure of the complex is that of a 7t-stacked system that constrains the distance between the two heavy atoms involved in the proton transfer, C and O, to a distance of 3.3A (Scheme 2.10) [20]. Conversely, for the napthol photoacids-carboxylic base pairs no such constraints are imposed so that there can be close approach of the two heavy atoms. The distance associated with the crossover between nonadiabatic and adiabatic proton transfer has yet to be clearly defined and will be system specific. However, from model calculations, distances in excess of 2.5 A appear to lead to the realm of nonadiabatic proton transfer. Thus, a factor determining whether a bimolecular proton-transfer process falls within the adiabatic or nonadiabatic regimes lies in the rate expression Eq. (6) where 4>(R), the distribution function for molecular species with distance, and k(R), the rate constant as a function of distance, determine the mode of transfer. 

Silicon tetraisothiocyanate (26.0 g., 0.10 mole) (Note 10) is finely ground under 100 ml. of anhydrous benzene, and the mixture is quickly transferred to a 1-1. round-bottomed flask. The mortar and pestle are washed with two 25-ml. portions of anhydrous benzene, and the washings are added to the flask. A solution of 2,6-dimethylaniline (48.5 g., 0.4 mole) (Note 1) in 100 ml. of anhydrous benzene is added to the well-stirred mixture. The reaction is mildly exothermic. The mixture is heated at the reflux temperature for 30 minutes, and the benzene is then removed using a rotary evaporator. Dilute isopropyl alcohol (200 ml.) (Note 5) is added to the residue, and the resulting mixture is heated at the reflux temperature for 30 minutes. The mixture is then processed in exactly the same manner as described above for the preparation of cyclohexylurea. The crude 2,6-dimethylphenylthiourea (m.p. 193-197°, 71.3 g., 99% yield) is recrystallized from 280 ml. of isopropyl alcohol (Note 8) to give 50 g. (72%) of product, m.p. 201-202°. Concentration of the mother liquor affords 11 g. (15%) of less pure product, m.p, 197-199° (Note 11). 

Rate data for the Menshutkin reaction between strongly activated Z-substituted benzyl / -toluenesulfonates and Y-substituted lV,lV-dimethylanilines in MeCN at 35 °C fit the equation kohs = h +k2 [DMA], which is consistent with concurrent first- and second-order processes.The 5 nI constant ki is unaffected by changing the nucleophile and conforms to Yukawa-Tsuno treatment with p — -5.2 and r — 1.3. The 5 n2 constant k2 was increased by electron-donating substituents in the nucleophile and showed upward curvature when subjected to the Brown a + treatment. 

In summary, although the BH model predicts an inverted region for the kinetics of proton in the nonadiabatic regime, the BH model is only in qualitative accord with the data derived from the proton transfer within the benzophenone-N, A -dimethylaniline contact radical ion pairs. The failure of the model lies in its ID nature as it does not take into account the degrees of freedom for the vibrations associated with the proton-transfer mode. By incorporating these vibrations into the BH model, the LH model provides an excellent account of the parameters serving to control the kinetics of nonadiabatic proton transfer. A more rigorous test for the LH model will come when the kinetic deuterium isotope effects for benzophenone-A, A -dimethylaniline contact radical ions are examined as well as the temperature dependence of these processes are measured. 

In recent years, there have been many signihcant advances in our models for the dynamics for proton transfer. However, only a limited number of experimental studies have served to probe the validity of these models for bimolecular systems. The proton-transfer process within the benzophenone-A, A-dimethylaniline contact radical IP appears to be the hrst molecular system that clearly illustrates non-adiabatic proton transfer at ambient temperatures in the condensed phase. The studies of Pines and Fleming on napthol photoacids-carboxylic base pairs appear to provide evidence for adiabatic proton transfer. Clearly, from an experimental perspective, the examination of the predictions of the various theoretical models is still in the very early stages of development. 

The inhibition of hydrocarbon oxidation by aromatic tertiary amines which contain no labile hydrogen, such as N,N-dimethylaniline and N,N,N, N -tetramethyl-p-phenylenediamine, has been assigned to an electron-transfer process. However, this seems rather unlikely as pyridine... 

Copolymerization of methyl methacrylate with styrene in the presence of isotactic poly(methyl methacrylate) has been examined by O Driscoll and Capek. Copolymerization was carried out in acetone at O C and redox system benzoyl peroxide -dimethylaniline was used to initiate the polymerization process. Carrying out the process with various ratios of styrene to methyl methacrylate, it was found that the polymerization rate drops very quickly with the increase in styrene concentration. A very small amount of styrene destroys any template effect that it-poly(methyl methacrylate) exerts on the rate of the polymerization. Assuming, that the reactivity ratios are not changed by the template (ri = i2 = 0.5), the critical length of the sequence of methacrylic units is 10- 20. Complexation occurs only if longer sequences, composed of methacrylic... 

The effect of exciplex dissociation (process MC) on the over-all kinetics of molecular fluorescence decay has been examined by Ware and Richter34 for the system perylene-dimethylaniline in solvents with dielectric constants (e) varying from 2.3 to 37. In low dielectric media (e = 2.3-4) the perylene fluorescence response may be fitted to a two-component exponential curve and exciplex emission is also observed, whereas in more polar solvents (e > 12) exciplex fluorescence is absent (at ambient temperatures) and the molecular fluorescence decays exponentially. These observations are consistent with both an increase in exciplex stability toward molecular dissociation with solvent polarity (Eq. 13) and the increased probability of dissociation into solvated ions... 

One function of amine and other basic promoters may be to facilitate cluster transformation by allowing facile protonation/deprotonation processes to occur. The [Rhl3(CO)24H3]2 cluster is a sufficiently strong acid to be deprotonated by NMM, as seen in (44). The HRh(CO)4 species has been found to be fully deprotonated by NMM and A.A-dimethylaniline... 

Figure 5. Glass capillary gas chromatogram of airborne aromatic amines in a film processing laboratory nitrogen selective detection. Peak identities 1, N,N-diethylaniline 2, 2,6-dimethylaniline (internal standard) 3, N,N-diethyl-1,4-di-aminobenzene 4, N,N -diisopropyl-1,4-diaminobenzene 5, not identified.

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