Dinitroanilines, hydrogenation

Hydrogen chloride, Chlorine, Dinitroanilines Hydrogen peroxide... 

Formation of diamines from dinitro compounds, which are unable to interact intramolecularly, presents no problem. Very large volumes of diaminotoluene, a precursor to toluene diisocyanate, are produced by hydrogenation of dinitrotoluene over either nickel or palladium-on-carbon. Selective hydrogenation of one or the other of two nitro groups is much more of a challenge, but a number of outstanding successes have been recorded. A case in point is the hydrogenation of 2,4-dinitroaniline (11) to 4-nitro-l,2-benzenediamine (12) (2) or to 2-nitro-l,4-benzenediamine (10). 

There are a few similarities between this accident and the previous one. When dinitroanilines (all isomers) are submitted to the effect of hydrogen chloride in the presence of chlorine, which seems to play a catalytic role, they give rise to a very violent reaction after a period of induction that can be very long if the temperature is low. Again a large volume of gas is also released. 2,3-Dinitroaniline is the most reactive, 3,5-the less reactive. 

Hydrochloric acid, Dinitroanilines See Hydrogen chloride Chlorine, Dinitroanilines... 

Benzenediazonium hydrogen sulfate, 2318 6-Bromo-2,4-dinitrobenzenediazonium hydrogen sulfate, 2097 2-Chloro-4,6-dinitroaniline, Nitrosylsulfuric acid, 2153 6-Chloro-2,4-dinitrobenzenediazonium hydrogen sulfate, 2102 2-Chloro-5-trifluoromethylbenzenediazonium hydrogen sulfate, 2647 2-Cyano-4-nitrobenzenediazonium hydrogen sulfate, 2668 2,6-Dichloro-4-nitrobenzenediazonium hydrogen sulfate, 2106... 

Hydrogen chloride, Chlorine, Dinitroanilines, 3993 Hydrogen chloride, Sulfuric acid, 3993 Hydrogen peroxide, Catalyst (unspecified), 4477... 

Hydrogen displacement from unsymmetrical substrates like 1,3-dinitrobenzene can produce a mixture of products. Reaction of 1,3-dinitrobenzene with hydroxylamine produces a mixture of 2,4-dinitroaniline and 2,6-dinitroaniline l,3-diamino-2,4-dinitrobenzene is formed if two equivalents of hydroxylamine are employed. °... 

The synthesis of TATB (14) from the reaction of 2,3,4,5,6-pentanitroaniline (31) with ammonia has been reported. " In one route, 2,3,4,5,6-pentanitroaniline (31) is synthesized from the nitration of 3,5-dinitroaniline (30) " the latter is obtained from the selective reduction of TNB ° or via a Schmidt reaction with 3,5-dinitrobenzoic acid. Another route to 2,3,4,5,6-pentanitroaniline (31) involves the selective reduction of TNT (1) with hydrogen sulfide in ammonia followed by nitration of the resulting 4-amino-2,6-dinitrotoluene (46), during which the methyl group is lost by oxidation-decarboxylation. 

Fig. 13. a Structure of the [18]crown-6 2,4-dinitroaniline 1 2 complex 231 b as seen nearly perpendicular to the plane of the crown, and the intermolecular hydrogen bonds23)... 

The guest molecules in the 1 2 [18]crown-6 2,4-dinitroaniline complex 21) are related by an inversion center (Fig. 13) 23). Both hydrogen atoms of the amine are involved in bifurcated hydrogen bonds. 

The mixture is heated to 450, and with good stirring hydrogen sulfide is passed into the reaction mixture while its temperature is maintained between 450 and 550 (Notes 2 and 3). The yellow suspended particles of 2,4-dinitroaniline dissolve slowly to form an intensely red-colored solution. The reaction is complete when all the yellow particles have disappeared reduction should be complete in thirty to sixty minutes (Note 4). 

A solution of sodium nitrite in concentrated sulphuric acid, which provides a nitrosonium hydrogen sulphate reagent, is a very effective diazotising medium which is particularly valuable for even more weakly basic amines, such as 2,4-dinitroaniline or the corresponding trinitro compound, picramide. 

Bromo-2,4-dinitrobenzenediazonium hydrogen sulfate, 2090 6-Chloro-2,4-dinitrobenzenediazonium hydrogen sulfate, 2095 2-Chloro-4,6-dinitroaniline, Nitrosylsulfuric acid, 2146... 

Under II tribromaniline adds hydrogen chloride but is a weak base. Nitro groups are more effective than the halogens in decreasing basicity, and dinitroaniline does not add on hydrogen chloride at all. Amido-phenol is a weak base and so is phenylhydroxylamine. 

Reduction. sym-Trinitrobenzcne, when reduced with sodium- or ammonium sulphide, forms 3,5-dinitroaniline. By treating it with hydrogen sulphide in alcoholic solution dinitrophenylhydroxylamine may be formed ... 

Lyle and LaMattina selectively hydrogenated 4-substituted 2,6-dinitroanilines to the corresponding nitrophenylenediamines over 10% Pd-C in 1,2-dimethoxyethane-chloroform as solvent (eq. 9.56).135 With use of ethanol instead of 1,2-di-methoxyethane, 4-trifluoromethyl-2,6-dinitroaniline was completely hydrogenated to give the corresponding triaminobenzene. 

Pd-C in both ethanol and DMF, little, if any, selectivity was obtained product ratios were 50 50 in ethanol and 60 40 in DMF. Palladium black in ethanol, which afforded 4-amino-5-nitroveratrole in 70-75% yield from 4,5-dinitroveratrole, provided no selectivity with 2,4-dinitroaniline, as well as with o- and m-dinitrobenzenes both nitro groups were hydrogenated.140 Reduction by sodium borohydride and Pd-C in methanol also does not appear to be selective, as 1,2,4-triaminobenzene is formed.141 It is of interest that over Pt-C in acidic alcohol 2,4-dinitroaniline is selectively hydrogenated at the 4-nitro group to give 4-amino-2-nitroaniline in 70% yield.142... 

SAFETY PROFILE A highly corrosive irritant to the eyes, skin, and mucous membranes. Mildly toxic by inhalation, Explosive reaction with alcohols + hydrogen cyanide, potassium permanganate, sodium (with aqueous HCl), tetraselenium tetranitride. Ignition on contact with aluminum-titanium alloys (with HCl vapor), fluorine, hexa-lithium disilicide, metal acetylides or carbides (e.g., cesium acetylide, rubidium ace-tylide). Violent reaction with 1,1-difluoro-ethylene. Vigorous reaction with aluminum, chlorine + dinitroanilines (evolves gas). Potentially dangerous reaction with sulfuric acid releases HCl gas. Adsorption of the acid onto silicon dioxide is exothermic. See also HYDROGEN CHLORIDE (AEROSOL) and HYDROCHLORIC ACID. 

Selective hydrogenation of one or two nitro groups in an aromatic dinitro compound is the basis for the synthesis of otherwise unattainable molecules. Carefully chosen catalysts, under totally different reaction conditions, have been met with success. Partial reduction of 2,6-dinitroanilines to nitrophenylenediamines occurs in 60-90% yield over 10% palladium-on-carbon at RT [equation (a)], although most heterogeneous catalysts do not afford such selectivity. 

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