2,6-Xylidine formation

As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant. Pinene explodes sharply acetone and ethanol ignite, then explode ether evolves gas, then explodes after a few s delay. Small amounts of primary aromatic amines-aniline, toluidines, xylidines, mesidine-ignite on contact, while larger amounts exploded dangerously, probably owing to rapid formation of diazonium perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar reason). 

The extent of methemoglobin formation from xylidines appears to be species dependent, with cats more susceptible than humans and dogs less susceptible. Administered intravenously to cats, 0.28 mM/% produced 10% methemoglobin in cats, whereas similar exposure in dogs did not produce methemoglobin. ... 

Typical primary amines which undergo such nitrosation are m-toluidine, p-xylidine, m-anisidine, 2-amino-4-methoxytoluene, 3-amino-4-methoxy-toluene, m-aminophenol, a-naphthylamine, l-naphthylamine-2-, -6-, -7-, and -8-monosulfonic acids, and l-naphthylamine-4-monosulfonic acid (which reacts with displacement of the sulfonic acid group). The secondary amines derived from these primary amines also can be nitrosated directly (i.e., without the intermediate formation of an JV-nitroso compound which needs to be subjected to the Fischer-Hepp rearrangement). The entering nitroso group appears to substitute exclusively in the para position. 

Conversion of Phenols to Amines. Aniline and some diphenylamine are formed when phenol and NHs solution are heated under pressure in the presence of FeCh, Al(OH)s, or Fe(OH)j. When NH and phenol or ortho-or para-cresols are reacted in the vapor phase over an AljO catalyst, yields of up to 88 per cent of the corresponding amines are obtained. However, these amines are customarily obtained by reducing the parent nitro compound, except in cases where it is difficult to obtain the required nitro isomer. For example, it is considered that the amination of symr xylenol is the best method of preparing sym-xylidine (l-amino-3,5-di-methylbenzene). When sym-xylenol is heated under pressure to 320 C with ammonium chloride, about equal amounts of sj/m-xylidine and sym-dixylylamine (5-imino-bis-l,3-dimethylbenzene) are formed. The ortho-and para-nitrophenols and nitrocresols can be aminat more readily. 2-Nitro-p-cresol [OH(l), N02(2), CHj(4)] and o-nitrophenol have been aminated in aqueous ammonia containing ammonium salts of weak acids to inhibit decomposition. Phosphoric, boric, carbonic, and formic acids were used. In one case it is claimed that 55-65 per cent yields of 2-nitro-p-toluidine (MNPT of commerce) were obtained when 2-nitro-p-cresol, 28 per cent aqueous NHj, and monoammonium phosphate, 1 11.5 0.2 molar ratio, were heated under pressure for 10 hr at 140-150°C and then 5 hr at about 160 C. Earlier workers, employing somewhat similar conditions, claimed excellent yields of MNPT when 1 mole of ammonium formate was used per mole of 2-nitro-p-cresol. ... 

One of the problems to be solved for the formation trend of Hofmann-(long-carbon-chain a,oo-diaminoalkane)-type series of inclusion compounds is to interpret the reason why Hofmann-dahxn-type host cannot accommodate xylidines as guest, which Hofmann-dabn-type host can do even with the shorter carbon chain in the full length than dahxn. In order to solve the problem we need more information about the crystal structures of the series. The structure analyses of Hofmann-dahxn-type m-and p-toluidine inclusion compounds are in progress. 

The formation of aniline from benzene has been mentioned in the introduction. > > Similarly, xylidine is obtained when hydrazoic acid... 

However, xylidine (which is apparently prefoable to toluidine) also has disadvantages. Its sulfate is only sparingly soluble in water so that if oxidation of sulfur dioxide occurs in the solution or if sulfur ttioxide is present in the gas stream, precautions must be taken to prevent the formation of crystals and subsequent plugging of equipment. The solubility of xylidine sulfite in the solvent is also not as high as would be desirable. At 20 C, for example, crystallization occurs when the concentration of sulfur dioxide reaches 108 g/1 (Pastnikov and Astasheva, 1940). Because of this, xylidine is normally used in a mixture with water. Xylidine sulfite is quite soluble in water so that crystallization is avoided, and when sufficient suitin dioxide has been absorbed, the xylidine-water mixture becomes a single phase. 

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