2.4- Dinitroaniline preparation

Dinitroaniline. This preparation is another illustration of the mobile character of the chlorine atom in 2 4-dinitro-l-chlorobenzene ... 

The synthesis of nitro dyes is relatively simple, a feature which accounts to a certain extent for their low cost. The synthesis, illustrated in Scheme 6.5 for compounds 140 and 141, generally involves a nucleophilic substitution reaction between an aromatic amine and a chloronitroaromatic compound. The synthesis of C. I. Disperse Yellow 14 (140) involves the reaction of aniline with l-chloro-2,4-dinitroaniline while compound 141 is prepared by reacting aniline (2 mol) with compound 144 (1 mol). 

Procedure. A hexane solution of Compound 118 is diluted or concentrated so as to bring the 118 content within a range of 15 to 150 micrograms per ml. In cases where the hexane solution requires concentration, the evaporation is carried out in a beaker on a steam bath with a gentle stream of air passing over the surface. The concentrated or diluted solution of 118 is washed with hexane into a volumetric flask and made up to volume with the hexane washings. One milliliter of the adjusted Compound 118 solution is precisely measured into a spectrophotometer cell, 2 drops of phenyl azide are added, and the dihydrotriazole is quantitatively formed and then treated with diazotized dinitroaniline to produce the red color as in the preparation of the standard curve. A blank, starting with 1.0 ml. of hexane and 2 drops of azide, is run at the same time. 

During the preparation of 2,4-dinitroaniline by a well-established procedure involving heating the reactants in a direct-fired autoclave (170°C and 40 bar were typical conditions), a sudden increase in temperature and pressure preceded a violent explosion [1], An alternative process avoiding the use of a sealed vessel is now used [2], See 2-Chloronitrobenzene Ammonia See polynitroaryl compounds bases, or salts See Other AMINATION INCIDENTS... 

This technique is used to diazotise anilines carrying two or more electron-withdrawing substituents, such as 2,4-dinitro- and 2-cyano-4-nitro-aniline, as well as aminoanthra-quinones and heteroaromatic amines [4]. Some diazonium salts prepared by this technique, such as those from 6-halogeno-2,4-dinitroanilines, are unstable in water and have to be added directly to the coupling component solution. 

For orange colours, simple 2-naphthol derivatives are the most commonly used coupling components as, for instance, in 2,4-dinitroaniline—>2-naphthol (4.118 Cl Pigment Orange 5). As in the yellow series, superior disazo pigments can be prepared using 3,3 -dichlorobenzidine as tetrazo component with derivatives of 1 -phenyl-3-methylpyrazol-5-one as couplers. 

Nitrosylsulfuric acid, prepared by dissolving sodium nitrite in concentrated sulfuric acid, is employed for amines of low basicity, whose diazonium salts will hydrolyze in dilute acid. In order to synthesize Pigment Orange 5, for instance, 2,4-dinitroaniline is dissolved in concentrated sulfuric acid and diazotized preferably with nitrosylsulfuric acid. Coupling is carried out with a (3-naphthol suspension, produced by acidifying a sodium naphtholate solution. 

Weakly nucleophilic amines such as 2,4-dinitroaniline are acylated in excellent yields by the mixed anhydride 301, prepared from the trimethylsilyl esters 299 (R = Me, i-Pr, t-Bu, PhCH2CH2, 2-MeCgH4 etc.) and 4-trifluoromethylbenzoic anhydride (300) under titanium(IV) catalysis 340... 

Preparation of poly[bis-(L-leucine)-l,6-hexylene] diester-co-trans-epoxysuccinic dinitroaniline... 

This method cannot be applied to polynitro amines, since these are so weakly basic that they can be diazotised only under special conditions in strongly acidic media (Section 6.7.1, p. 922). In such cases use may be made of the susceptibility to nucleophilic displacement of halogen when activated by ortho and para nitro groups. Thus the valuable reagent 2,4-dinitrophenylhydrazine (Expt 6.93) is readily prepared by reacting l-chloro-2,4-dinitrobenzene with hydrazine. Reaction with ammonia similarly gives 2,4-dinitroaniline (cognate preparation in Expt 6.93). 

Dinitroaniline herbicides. Trifluralin (Treflan ), a 4-trifluoromethyl substituted 2,6-dinitroaniline derivative, was the first main fluorine-containing herbicide to be marketed, with 18,000 tons sold in 1982 in the United States alone [16]. Trifluralin, which was introduced in 1960 by Eli Lilly, is a pre-emergence herbicide used in soybean for the control of a variety of grass and broadleaf weeds [17]. It is prepared from the nitration of 4-chlorobenzotrifluoride, followed by nucleophilic displacement of chlorine with di-n-propyl amine (Fig. 3). Following the success of trifluralin, a number of related A/,A/-dialkyl 4-trifluoromethyl 2,6-dinitroaniline herbicides were later introduced [18]. 

Dinitroaniline has been prepared by heating dinitrochlorobenzene and ammonia under pressure 1 by heating... 

Trinitrobenzene cannot be obtained by the nitration of o- dinitrobenzene. Kamer and Contardi have prepared this isomer from 2,6-dinitroaniline ... 

Chemical properties. A chlorine atom ortho or para to a nitro group is especially reactive and is readily substituted. Numerous examples of such reactions, utilized in the preparation of explosives, are given later in the descriptions of preparation methods for dinitrophenol, dinitroanisole, hexanitrodiphenylamine, hexanitro-diphenyl sulphone, dinitroaniline, tetryl, etc. Chlorodinitrobenzene reacts with sodium sulphide and sulphur to yield sulphur dyes. The action of sodium disulphide results in the formation of tetranitrodiphenyl sulphide (p. 554). 

Nowadays 2,4-dinitroaniline is prepared on a large scale by treating chloro-dinitrobenzene with ammonia. The method was first reported by Engelhardt and Lachinov [9] in 1870. Heating 2,4-dinitrophenol with an excess of urea at 208°C... 

Kym [10]) is another convenient method of preparation of 2,4-dinitroaniline. Further nitration of 2,4-dinitroaniline leads to 2,4,6-trinitroaniline (picramide). 

Dinitroaniline is usually obtained from 1,3,5-trinitrobenzene by reduction of a nitro group with sodium hydrosulphide. It may be used as starting material for the preparation of pentanitroaniline. 

Dinitroaniline has been prepared by the ammonolysis of 2,6-dinitroanisole,3 2,6-dinitroiodobenzene,4 2,6-dinitrophenyl 4-nitrobenzyl ether,8 and 2,6-dinitrochlorobenzene 6 by the rearrangement of o-nitrophenylnitramine 7 and by the desulfo-nation of potassium 4-amino-3,5-dinitrobenzenesulfonate. 9 The method described above is based upon the procedures of Ull-mann 8 and Welsh. ... 

Technical Observations. Dinitrochlorobenzene is manufactured on a very large scale, and is used in the preparation of sulfur black T (q.v.) and other important dyes. It is, moreover, the starting material for a whole series of condensation products made by replacing the very labile chlorine atom by basic and other residues. Thus, it is easy to prepare dinitroaniline and dinitrophenol, as well as picric acid and dinitroanisole, from dinitrochlorobenzene. The accompanying formulas show only a small part of the reactions actually used (also see Table V). 

While the nitrite must be used in exactly the amount theoretically required, an excess of acid is always used. For laboratory preparations, as a rule, the excess acid used is about 0.5 equivalent over the theoretically required 2 equivalents. The excess of acid must be increased to 1 to 3 equivalents in diazotizations of weakly basic amines whose salts are readily hydrolyzed (e.g., chloro- and nitroanilines). In some cases where even this larger excess of acid is insufficient to dissolve the base (e.g., nitrochloroaniline), the diazotization may be carried out in suspension provided that the base is present in a finely divided state. Thus, a solution of the base in concentrated sulfuric acid may be poured into ice water, the base filtered off and washed and then made up into a paste. Even this method fails to work with some bases such as dinitroaniline and m trodichloroaniline these compounds can be diazotized smoothly only in concentrated sulfiuric acid solution. 

For preparation of (2), Phosphorus(V) Oxide (60 mmol) is added with stirring to 25 mL of DMF at 0 °C. After 30 min. Dimethyl Sulfoxide (60 mmol) is added. After stirring for 1 h, 20 mmol of 2,4-dinitroaniline in 25 mL of DMF is added drop-wise at 0°C with continued stirring. After 3 h, 180 mmol of Triethylamine is added at 0-5 °C, and stirring is continued for 3 h. The deposited crystals are collected by filtration and recrystallized from THF. The yield of orange crystalline material is 96% based on 2,4-dinitroaniline. ... 

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