Replacement of hydrogen by nitrogen

Direct replacement of an amino group by hydrogen is possible only in certain cases. Such reductive fissions are particularly well known for tertiary amines and quaternary ammonium compounds and occur especially readily with allyl- and benzyl-substituted amines. In the last-mentioned cases the benzyl group is removed as toluene, and this reaction route is used for preparation of secondary from primary aliphatic amines the primary amine is first condensed with benzaldehyde, and the resulting Schiff base is reduced to the alkylbenzylamine this is converted by alkylation into the dialkylbenzyl-amine, from which finally the benzyl group is removed by catalytic hydrogenation 544 

Some preparative importance attaches also to reductive deamination of tertiary Mannich bases, which are accessible by condensation of a CH-acidic compound with formaldehyde and a secondary aliphatic amine. By this route 

These reductive deaminations can be effected by hydrogenation over Raney nickel, palladium, or copper chromite catalysts, and also by means of sodium amalgam or zinc dust in aqueous-methanolic sodium hydroxide.344k 

Substitution of hydrogen for a primary amino group attached to an aromatic nucleus is carried out almost exclusively by decomposing the derived diaz-onium compound with reducing agents such as alcohols, hypophosphorous acid, formaldehyde in alkaline solution, or tin(n) compounds.546 

The usual procedure is to drop the freshly prepared diazonium salt solution at 0° into a cooled and stirred 50% hypophosphorous acid solution the reaction mixture is set aside at 0-5° for several hours after evolution of the nitrogen and is then worked up. 

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Yuvaraj S, Chang T-H and Yeh C-T (2003), Low-temperature-programmed replacement of nitrogen by hydrogen in pores of mordenite , J Phys Chem B, 107, 4971. 

The replacement of nitrogen by hydrogen stream during the thermal pretreatment of the catalysts as well as in the reactor causes a dramatic effect in the catalytic properties of the nickel-containing samples 2 and... 

The reverse order of replacement of halogens, i.e. preferential substitution of chlorine rather than of bromine by hydrogen in bromochloro compounds, is possible if chlorine is activated by its position in the molecule. For example, 5-bromo-6-chloro-2,4-dimethylpyrimidine, in which chlorine is rendered labile by its a-position to one of the ring nitrogens, is reduced to 5-bromo-2,4-dimethylpyrimidine by refluxing with p-toluenesulfonylhydrazine in chloroform (equation 28). ... 

The activity and selectivity of 12.5% M0/AI2O3 nitrided at various temperatures for the hydrodesulfurization (HDS) of dibenzothiophene and the effect of re-treatment of NH3 on dibenzothiophene HDS were studied. The nitrided catalyst was significantly more active toward the scission of the C-S bond from dibenzothiophene with hydrogenation of dibenzothiophene. The sulfur species accumulated on the surface of the nitrided M0/AI2O3 catalysts by replacement of nitrogen species after reaction was analyzed by XPS measurement. The formation of molybdenum sulfide during the HDS dibenzothiophene led to a decrease in the activity of the nitrided catalyst, which approached that of the sulfided catalyst. 

Pyrazolin-5-ones react with salts of various metals to form compounds in which the pyrazolinone has reacted in its enolic form with replacement of the enolic hydrogen to give a salt and having semipolar bonds formed by donation of electrons to the metal by the nitrogen atoms393 394 Usually these compounds contain the number of pyrazolinone residues corresponding to the valence of the metal atom. Such salts as cuprous iodide, ferric iodide, cobaltous iodide, silver iodide and silver diiodide participate in such reactions.393,394 In addition, complexes may be formed in which there has been no elimination of a small molecule between the reactants and no formation of ionic bonds.432... 

According to this conception of the reaction, the diazonium salt is formed as the result of the replacement of the three hydrogen atoms in the salt of the amine by the trivalent nitrogen atom of nitrous acid. 

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