Ammonia precursor

Hexamethylenetetramine this ammonia precursor does not cause fibre swelling and the unfixed dyes are removed efficiently at pH 6.5, compared with pH 8.5 with ammonia, thus causing less damage to the wool. However, the hydrolysis of this compound (Scheme 12.6) results in the formation of formaldehyde and this can modify the hue of certain dyes [2]. 

In fact, NO accounts for 90-95% of NO in exhausts. Aqueous ammonia or urea, as ammonia precursor, are typically employed. The term selective refers to the unique ability of ammonia to react selectively with N instead of being oxidized by oxygen. 

NH2, OH ammonia precursors NH4OAC, (NH4)2C03 catalyst zeolite, AI2O3, p-TSOH, CSA, Ti(0/-Pr)4, microwave solvent MeOH, EtOH, H2O, toluene, DMF, ionic liquid... 

The application of fertilizer to soil, as ammonia, ammonium compounds, or ammonia precursors (such as urea), is a well documented source of ammonia release to the atmosphere (ApSimon et al. 1987 Beyrouty et al. 1988 Buijsman et al. 1987 Kucey 1988 Olivier et al. 1998 Reynolds and Wolf 1988). The rate of ammonia emission from ground sources, such as freshly fertilized fields and cattle feedlots, is dependent on variables such as the pH, temperature, soil characteristics, rainfall, method of application, wind speed, etc. (Bouwmeester and Vlek 1981 Brunke et al. 1988 Denmead et al. 1982 Hoff et al. 1981 Kucey 1988 Nason et al. 1988 Reynolds and Wolf 1988). Ammonia can volatilize from sewage sludge that has been spread on the surface of the soil (Beauchamp et al. 1978 Ryan and Keeney 1975) as well as from poultry litter (Brinson et al. 1994). In the latter case, composted poultry litter released far less volatile NH3 to the atmosphere (0-0.24% of applied) than did fresh poultry litter (17-23%) (Brinson et al. 1994). In contrast, the crops themselves are often minor sources of atmospheric NH3. Harper and Sharpe (1995) demonstrated almost no net atmospheric NH3 flux in com crops, due to their relatively similar emission and uptake rates of NH3 over the growing season. 

Urea as Ammonia Precursor Compound 16.2.1 Solid Urea... 

Alternative Ammonia Precursor Compounds 16.3.1 Cyanuric Acid... 

Historically, cyanuric acid can be considered one of the first ammonia precursor compounds. As far back as 1977, a Japanese patent mentions the possibility of replacing NH3 in power plant exhaust gas aftertreatment with inorganic ammonium salts, urea or cyanuric acid granules of 0.1-10 mm diameter [59]. However,... 

Krocher O, Elsener M, Jacob E (2009) A model gas study of ammonium formate, methanamide and guanidinium lormate as alternative ammonia precursor compounds for the selective catalytic reduction of nitrogen oxides in diesel exhaust gas. Appl Catal B 88(l-2) 66-82... 

LNT, and SCR-NH3 bricks [76]. Finally, one recent invention relates to the SCRF concept where an emission treatment system for treatment of an exhaust gas stream contains PM and NO [74]. The process includes an oxidation catalyst, an injector that periodically meters ammonia precursor (e.g., urea) into the exhaust stream, and a wall-flow monolith. The injector is in fluid communication with the oxidation catalyst in order to favor the decomposition of urea (CO (NH2)2) into ammonia and is positioned downstream of the oxidation catalyst The oxidation catalyst (e.g., PGM or Pt/zeolite) is also useful for oxidating NO to NO2 to provide an N02-enriched exhaust stream and combusting, substantial portions of the PM in particular the SOF. In some examples, the oxidation catalyst is disposed on a honeycomb flow through monolith substrate or an opencell foam substrate. 

Bromosafrole is a great stepping stone to final product and was, in fact, the exact precursor used by Merck who was the first person to synthesize MDMA. Until very recently it was the defacto method that most underground chemists started out with (Someone-Who-Is-Not-Strike included) because, at first glance, it seems so simple and uses basic chemicals and equipment. Once someone has the bromosafrole, all one has to do is just swap out that Br with simple ammonia or methylamine and the deed is done. 

Several substituted cyclohexane derivatives may also be obtained by the reduction of a benzenoid precursor. Partial reduction of resorcinol, for example, and subsequent methyla-tion yields 2-methylcyclohexane-I,3-dione, which is frequently used in steroid synthesis (M.S. Newman, 1960 see also p. 71f.), From lithium-ammonia reduction of alkoxybenzenes l-alkoxy-l,4-cyclohexadienes are obtained (E.J. Corey, 1968 D). 

Nitriding Metals or Metal Hydrides. Metals or metal hydrides may be nitrided using nitrogen or ammonia. Pure metal powders or pure metal hydride powders yield nitride products that are nearly as pure as the precursors. 

The primary use of a-picoline (2) is as a precursor of 2-vinylpyridine (23). It is also used in a variety of agrochemicals and pharmaceuticals, such as nitrapyrin [1929-82-4] (60) to prevent loss of ammonia from fertilizers picloram [1918-02-1] (61), a herbicide and amproHum [121 -25-5] (62), a coccidiostat. 

A hquid-phase reaction in which TiCl is reacted with hquid ammonia at —35 C to form an adduct that is subsequendy calcined at 1000°C has also been proposed (35). Preparation of titanium nitride and titanium carbonitride by the pyrolysis of titanium-containing polymer precursors has also been reported (36). 

Caprolactam [105-60-2] (2-oxohexamethyleiiiiriiQe, liexaliydro-2J -a2epin-2-one) is one of the most widely used chemical intermediates. However, almost all of the aimual production of 3.0 x 10 t is consumed as the monomer for nylon-6 fibers and plastics (see Fibers survey Polyamides, plastics). Cyclohexanone, which is the most common organic precursor of caprolactam, is made from benzene by either phenol hydrogenation or cyclohexane oxidation (see Cyclohexanoland cyclohexanone). Reaction with ammonia-derived hydroxjlamine forms cyclohexanone oxime, which undergoes molecular rearrangement to the seven-membered ring S-caprolactam. 

Copper Hydroxide. Copper(II) hydroxide [20427-59-2] Cu(OH)2, produced by reaction of a copper salt solution and sodium hydroxide, is a blue, gelatinous, voluminous precipitate of limited stabiUty. The thermodynamically unstable copper hydroxide can be kiaetically stabilized by a suitable production method. Usually ammonia or phosphates ate iacorporated iato the hydroxide to produce a color-stable product. The ammonia processed copper hydroxide (16—19) is almost stoichiometric and copper content as high as 64% is not uncommon. The phosphate produced material (20,21) is lower ia copper (57—59%) and has a finer particle size and higher surface area than the ammonia processed hydroxide. Other methods of production generally rely on the formation of an iasoluble copper precursor prior to the formation of the hydroxide (22—26). 

Coppet(II) oxide [1317-38-0] CuO, is found in nature as the black triclinic tenorite [1317-92-6] or the cubic or tetrahedral paramelaconite [71276-37 ]. Commercially available copper(II) oxide is generally black and dense although a brown material of low bulk density can be prepared by decomposition of the carbonate or hydroxide at around 300°C, or by the hydrolysis of hot copper salt solutions with sodium hydroxide. The black product of commerce is most often prepared by evaporation of Cu(NH2)4C02 solutions (35) or by precipitation of copper(II) oxide from hot ammonia solutions by addition of sodium hydroxide. An extremely fine (10—20 nm) copper(II) oxide has been prepared for use as a precursor in superconductors (36). 

Nitrilotriacetonitrile [628-87-5], N(CH2CN)2, a precursor to nitrilotriacetic acid [139-13-9], N(CH2COOH)2, can be prepared from the reaction of formaldehyde cyanohydrin with ammonia (26). Formaldehyde cyanohydrin is also used as an intermediate in pharmaceutical production. Commercial formaldehyde cyanohydrin is available as a 70% aqueous solution stabiLhed by phosphoric acid. 

A.mina.tlon. Amination describes the introduction of amino groups into aromatic molecules by reaction of ammonia or an amine with suitably substituted halogeno, hydroxy, or sulfonated derivatives by nucleophilic displacement. Although reaction and operational conditions vary, the process always involves the heating of the appropriate precursor with excess aqueous ammonia or amine under pressure. 

Diaminoanthraquinone and Related Compounds. Leuco-l,4-diaminoanthraquinone [81-63-0] (leucamine) (32) is an important precursor for 1,4 diaminoanthraquinone [128-95-0] (33) and is prepared by heating 1,4-dihydroxyanthraquinone (29) with sodium dithionite in aqueous ammonia under pressure. 

Heterocyclic enamines A -pyrroline and A -piperideine are the precursors of compounds containing the pyrrolidine or piperidine rings in the molecule. Such compounds and their N-methylated analogs are believed to originate from arginine and lysine (291) by metabolic conversion. Under cellular conditions the proper reaction with an active methylene compound proceeds via an aldehyde ammonia, which is in equilibrium with other possible tautomeric forms. It is necessary to admit the involvement of the corresponding a-ketoacid (12,292) instead of an enamine. The a-ketoacid constitutes an intermediate state in the degradation of an amino acid to an aldehyde. a-Ketoacids or suitably substituted aromatic compounds may function as components in active methylene reactions (Scheme 17). 

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