Aniline producers

Rubber chemicals, primarily antioxidants (qv), stabiLhers, and antio2onants (qv), account for 12% of the demand for aniline woddwide. Important agricultural uses for aniline derivatives include fungicides, insecticides, animal repellents, and defoHants. It is estimated that less than 5% of the aniline produced in 1988 was consumed for agricultural chemicals. 

The symmetrical intermediate 5 can be attacked by the NH3 at either of two positions, which explains why about one-half of the aniline produced from the radioactive chlorobenzene was labeled at the 2 position. The fact that the 1 and 2 positions were not labeled equally is the result of a small isotope effect. Other evidence for this mechanism is the following ... 

Sn = 4H this must be borne in mind when calculating the quantities required for the reaction. The stannic chloride forms the complex chloro-stannic acid with hydrochloric acid, which combines with the aniline produced in the reaction ... 

In an in vitro assay with cultured human fibroblasts, aniline produced only marginal increases in sister chromatid exchanges at the highest dose tested, 10 mM whereas two metabolites of aniline, 2-aminophenol and jV-phenylhydroxylamine, doubled the frequency of sister chromatid exchanges at the highest tested nontoxic concentration, 0.1 mM (Wilmer et al. 1981). 

Note that 2 moles of HNO3 and 3 moles of H2 are needed for each mole of aniline produced from benzene. [Why are 4 moles of H2 required for the entire process ]... 

As is well known, the oxidation of aniline with various oxidizing agents leads to a variety of products, usually highly colored polymeric materials. However, the reaction with Caro s acid (permonosulfuric acid, H2SOs) with aniline produces nitrosoaniline rapidly [76]. With this reagent, many aromatic amines have been oxidized to the corresponding nitroso compounds, e.g., the three nitronitrosobenzenes were prepared from the corresponding nitroani-lines [77, 78]. The reaction is normally carried out in an aqueous medium. In... 

Pentosans. These compounds are polysaccharides which may he considered as anhydrides of pentose sugars, after the manner of the hexosans. sucrose, starch, from glucose, fructose. When pentosans or pentoses are heated with hydrochloric ot sulfuric acid, furfural C fljO CHO is formed, and addition of aniline produces a red color. Pentosans are present in gummy carbohydrates, in bran of wheat seed, and in woods. 

The primary aniline production process in the world is the hydrogenation of nitrobenzene. BASF, DuPont, ChemFirst (purchased by DuPont in 2002) and Rubicon use this process in the United States. This technology is also used by all Western European aniline producers and all but one Japanese aniline producer. 

Aniline s global production capacity in 1999 was 2.9 million tonnes, and demand in 2000 was estimated to be 2.68 million tonnes per year. The capacity in 1999 was found in these regions Western Europe - 47%, North America -30% and Asia / Pacific -19%140,256. In 2000 China had over 20 aniline producers with a total capacity that exceeded 200,000 tonnes per year. Aniline production in 1999 in China was 142,700 for a utilization rate of around 70%. Historical production in the United States is summarized in Table 20.2255. 

The concentration of the weak acid or of the weak base can be determined by distribution between water and another solvent, such as benzene or chloroform the partition coefficient of the acid or base between the water and the other solvent must, of course, be known. The degree of hydrolysis may then be calculated from the concentration of the salt and the determined concentration of the weak acid or base. An example of such a salt is aniline hydrochloride. This is partially hydrolysed into aniline and hydrogen chloride. On shaking the aqueous solution with benzene the aniline will distribute itself between the water and benzene in the ratio of the distribution coefficient. The initial concentration of aniline hydrochloride is known, the concentration of the free aniline in the aqueous solution can be computed from that found in the benzene solution, and from this the total concentration of aniline, produced by hydrolysis, is deduced. Sufficient data are then available for the calculation of the degree of hydrolysis. 

The amine is titrated with hydrochloric acid and sodium nitrite in very dilute solution, and the resulting diazonium salt is coupled with an accurately known amount of a phenol, usually SchaefiFer salt. With other compounds, such as H acid, amino R acid, etc., one sample is diazotized and another is coupled with diazotized aniline or other amine. Under some circumstances it is possible to determine two substances in mixture if one of them reacts much more rapidly than the other. Thus, with a little practice, one can determine quite accurately both G salt and R salt in mixtures of.the two. R salt couples very rapidly with diazotized aniline producing a red dye, while G salt couples more slowly and gives a yellow dye. A large number of other special methods are available which permit the determination of the individual constituents in mixtures. 

Enantiopure 1,4-disubstituted 2-imidazolines 1179 can be prepared from chiral P-amino alcohols 1175. The acylated alcohols, iV-hydroxyethylamides 1176, are reacted with excess thionyl chloride (or with thionyl chloride followed by phosphorus pentachloride) to yield A -chloroethylimidoyl chlorides 1177. Treatment of 1177 with amines or anilines produces iV-chloroamidines 1178, which were converted into imidazolines 1179 upon work-up with aqueous hydroxide (Scheme 287) <2002JOC3919>. 

The vapor phase N-alkylation of aniline with ethanol took place over an H-ZSM-5 catalyst at temperatures between 250° and 500°C. The maximum selectivity for N-monoethylation occurred at the lower temperatures with increasing amounts of diethyl aniline produced at higher reaction temperatures. v/ith montmorillonite catalyst, reaction at 400°C gave a 64% selectivity for N-ethyl aniline formation at 77% conversion. A vanadium exchanged montmorillonite was more active but less selective giving N-ethyl aniline in 48% selectivity and N, N-diethyl aniline in 37% selectivity at 97% conversion.94... 

The levels indicated by values 20, 232 and 339 kJ mol-1 correspond to A-protonated aniline produced by ion-molecule reactions (reagents depicted so in the insets) in the absence of collisional stabilization (a) lower ionized chlorobenzene-ammonia, (b) middle phenyldiazonium ion—ammonia and (c) upper phenyl cation-ammonia... 

The data in Table 1 clearly indicate that aniline produces more stable complexes than A-methylaniline. 

China is a relative latecomer to the aniline business, with extensive growth only in the 1990s. Nevertheless, by 2002, there were some 20 to 25 aniline producers, with total capacity of 280,000 metric tons per year, mainly by vapor-phase hydrogenation25. In 2000, Jiln Chemical Industries Corp., the only Chinese producer of MDI-grade aniline,... 

Thus, 9 and 10 are the major coupling products formed upon oxidation of aniline in aqueous H2SO4 solution. Theoretically, it is possible to imagine two mechanisms of the reaction pathway (i) dimers are formed by two radical cations coupling, and (ii) an electrophilic attack of the radical cation on a neutral molecule of aniline produces the corresponding dimer. In the second case it is assumed that the coupling product loses another electron and therefore the total number of electrons transferred in the overall processes would be the same in both mechanisms. 

Reaction of Cp 2Ta(CH2)H with water or aniline produced Cp 2Ta(E)H (E = 0, NPh) in which the reducing hydrido ligand co-existed with an oxo or phenylimido ligand.456 Unexpectedly, the TaNC bond in the phenylimido species was linear, consistent with a 20-electron count and the presence of a Ta=N bond. However, the TaN and TaO bond distances are intermediate between the values expected for double and triple bonds, indicating that the second it interaction is relatively weak. This conclusion is supported by the low energy (850 cm ) of the //(TaO) stretching mode. 

Two mechanistically plausible scenarios for nucleophilic attack on the q benzyl palladium species seem feasible. Formation of the C N bond could occur either via external attack of the amine through inversion of configuration at the carbon stereocenter, or alternatively the amine could coordinate to palladium followed by an internal attack on the q benzyl ligand. Mechanistic investigations [15] using stoi chiometric amounts ofthe enantio and diastereomerically pure q benzyl palladium complex [ (R) Tol BINAP [q 1 (2 naphthyl)ethyl Pd](OTf) (8) revealed that the re action with aniline produced predominantly (R) N1 (2 naphthyl)ethylaniline R) 9), consistent with external nucleophilic attack (Scheme 11.3) [15]. However, it was noted that the catalytic reaction of [ (1 ) Tol BINAP Pd(OTf)2] with vinyl arenes and amines produced preferentially the opposite enantiomeric (S) amine hydroamination... 

This asymmetric Mannich reaction could also proceed by an enamine pathway because nucleophilic addition of the in situ-generated enamine would be faster to an imine than to an aldehyde. As shown in the Fig. 12.59, the reaction starts with enamine 34 activation of the cyclohexanone by the proline anion and an electrostatic interaction with the imidazolium moiety of the catalyst In a second pre-equilibrium, the aldehyde and aniline produce an imine. Then enamine-activated 35 reacts with the imine to form 35 via transition state A. The last step is a dehydration reaction to afford the corresponding product. The catalyst is regenerated in the subsequent step. 

Only the anilines, produce similar chemical shifts, however, the resonance bands of the anilines are sensitive to the addition of acid to the sample solution while the phenols are not affected in the same manner. 

This older technique, which uses a mixture of iron filings and hydrochloric add to reduce nitrobenzene to aniline, is employed today only to produce iron oxide pigments, with aniline produced as a by-product... 

An interesting sequence of reactions used in the preparation of the quinolone derivative (25) has been presented.22 The isatin (26) was treated with base to afford the Pfitzinger rearrangement product (27). Although treatment of (27) with polyphosphoric acid gave the y-lactone (28), reaction in refluxing dimethyl-aniline produced the (5-lactone (29). Successive treatment of the latter with phosphorus oxychloride and potassium hydroxide gave the furoquinoline (25). 

Treatment of methyl 2-(methoxymethylene)acetoacetate (287) with aniline produced the corresponding enaminoketoester 288 in 97% yield. Formation of the orange Li salt followed by passage of dry gaseous formaldehyde at -78°C and warming gave the oxo-5-lactone 289. Facile conversion to the natural alkaloid was achieved in 66% yield through dissolution of 289 in liquid ammonia. The spectral data of the product confirmed that it was a mixture of the two isomers 285/286. Thus, for example, the methylene protons adjacent to the carbonyl appeared as two triplets at 2.45 and 2.50 ppm in the ratio of 1.5 2.5 (Scheme 26) (216). 

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