Hydrogenation nitrocompounds

The hydrogenation of organic nitrocompounds has received relatively little attention. The only reports on this... 

It is worth noting, however, that up until fairly recently the reduction of aromatic nitrocompounds to the corresponding amines was commonly performed on an industrial scale, e.g. in the synthesis of azo dyes, with a mixture of iron and hydrochloric acid. This so-called Bechamp reduction has an E factor of ca. 15 compared to 1 for catalytic hydrogenation. 

HTC (2) [Hydrogen transfer catalysis] A catalytic process for reducing aromatic nitrocompounds. Developed by Rohner in 1993. 

Ammonium hydrogen sulphide is also a very suitable reagent for the reduction of nitrocompounds to arylhydroxylamines it is used in alcoholic solution in the cold.1... 

The radical-anions of aliphatic nitrocompounds are detectable in aqueous solution as transient intermediates formed during continuous electrolysis in the cavity of the esr spectrometer [4], Decay of the species occurs by protonation and then further reactions. 2-Methyl-2-nitropropane has no acidic hydrogens so that it can be examined in aqueous alkaline solution where the radical-anion is not protonated. Over the pH range 9-11, this radical-anion decays by a first order process with k = 0.8 0.1 s at 26 C. Decay results from cleavage of the carbon-nitrogen bond to give a carbon centred radical and nitrite ion. Ultimately, the di-(ferr,-butyI)nitrone radical is formed in follow-up reactions [5],... 

The reduction of aliphatic nitrocompounds in acid solution proceeds in two steps. First the nitrosocompound is formed. A low steady state concen ation of 2-methyl-2-nitrosopropane has been detected during the reduction of 2-methyl-2-nitropropane [13]. At the cathode potential necessary to attach the first electron to a nitro group, the nitroso intermediate undergoes further reduction to the hydroxyla-mine. When the nitrocompound has one a-hydrogen substituent, tautomerism of the nitroso intermediate to an oxime is in competition with further reduction. Both temperature and proton availability affect the rate of this isomerisation. Reduction of aliphatic nitrocompounds to the hydroxylamine is usually carried out in acid solution at 0-5° C to minimise oxime formation [14, 15], The hydroxylamine is stable towards further reduction in acid solution. Oximes in acid solution are reduced... 

When a new carbon-carbon bond is produced by nucleophilic addition to conjugated systems, the process is called Michael addition. The generalised process involves an a, b-unsaturated compound and a compound containing an active hydrogen attached to a carbon atom (e.g., malonic ester, acetoacetic ester, nitrocompounds, aldehydes, ketones etc.) These are condensed in the presence of a base. The overall reaction and its mechanism can be represented as follows ... 

HYDROGEN BONDING OF NITROCOMPOUNDS WITH SULPHURIC ACID... 

RNOa + HsSO RNO, HOSO3H RNQ2H+ + HS04-which have been obtained in the crystalline phase (Part I), affects these liquid phase properties to various degrees, depending upon the stability of the addition compounds, which is the result of the basicity of the mononitrocompounds (Gillespie and Solomons J. Chcm. /She. 1957 1796). In order to explain some peculiarities, however, the disruption of the hydrogen bonded structure of sulphuric acid by the presence of the molecules of the nitrocompounds in the mixtures must be taken into account also. 

In order to discuss the meaning of these viscosity isotherms we are going to apply the ideas about the viscosity of binary systems developed by one of us elsewhere [3] and to make use of the known data about the ionizations of these nitrocompounds in sulphuric acid [-5, 6], The viscosity isotherm of the system with nitromethane, showing strong negative deviations from additivity, does not necessarily mean that nitromethane does not interact with sulphuric acid in the sense of hydrogen bond formation and basic ionization. Cryoscopic investigations have shown that nitromethane ionizes as a weak base in sulphuric... 

Alkalies, Action on Aliphatic Nitrocompounds. Compds with hydrogen atoms attached to a primary or secondary carbon atom linked to an NO, group show weakly acid properties. Such compds dissolve or react slowly in strong alkalies to form salts. This formation of salts is usually comparatively slow. 

The hydrogen transfer reaction between alcohols and nitrocompounds should pruceed according to the following equations ... 

However, for some electrocatalytic reactions, such as the electrooxidation of alcohols, aldehydes or acides, and also the electro reduction of oxygen, lead adatoms can exhibit a promoting effect (3-7). Moreover, lead can change the selectivity in the case of electrocatalytic reductions of nitrocompounds (8), whereas it inhibits the adsorption of hydrogen on platinum (9,10),... 

While this, under the influence of the oxidising action of the nitrocompound, loses two atoms of hydrogen, and thus quinoline is formed ... 

Aromatic hydroxylamines are generally prepared by chemical reduction or selective hydrogenation of aromatic nitrocompounds by using metal catalysts promoted with dimethylsulfoxide. However, such methods of synthesis are characterized by difficult products purification and low yields /1,2/. The low cost production of arylhydroxylamines can be of great practical interest because these compounds can undergo rearrangement to yield a variety of important chemicals 111. 

The remarkable lower specific activity, ri, observed on Ru/C is in agreement with previous literature results which indicate aithenium as the less active metal for the reduction of aromatic nitrocompounds / /. The lower selectivity can be related to the faster hydrogenation of the nitroarylhydroxylamines on this catalyst compared to Pt or Pd. In fact on Ru/C the conversion of the nitroaiylhydroxylamines to nitroamino isomers starts even in the presence of unreacted 2,4-DNT (see Figure lb). 

CIANOGUANIDINA (Spanish) (461-58-5) Mixtures with many compounds form explosive compounds, including strong oxidizers, diazo, nitrocompounds, salts of diazonium or hydrazinium, azides, tetrazenes, tetrazoles, triazenes, and triazoles. Reacts with strong acids, forming hydrogen cyanide. 

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