Ammonia sources

Urea acts not only as an ammonia source but also forms decomposition products, such as biuret and higher condensation products. 14C labeling has indicated that the carbon atom of the urea molecule is not incorporated into the phthalocyanine structure. Employing a phthalic anhydride molecule bearing one radioac-tively labeled carbonyl function affords labeled copper phthalocyanine and phthalimide (as a side product), while the liberated carbon dioxide was found not to show any radioactivity. Labeled carbon dioxide, on the other hand, has been obtained in corresponding experiments using 14C labeled urea. 

An entirely different approach has been developed by Carreira and coworkers [57], who used sulfamic acid as the ammonia source. In conjunction with dimethyl formamide (DMF), amination occurred via an imidate, which was formed in situ. Although only those examples with branched allyUc alcohols as substrates were reported, a promising enantiomeric excess was achieved with the novel phosphora-midite L9 (Scheme 9.24). 

In classical Hantzsch procedure, an enaminocarbonyl is formed in sim by condensation of ammonia source onto the 1,3-dicarbonyl substrate. But many groups have used a three-component modified-Hantzsch protocol in which the preformed enamine is introduced as a partner. Thus, utilization of cyclic or acyclic 1,3-dicarbonyl compounds, aldehydes, and acyclic or cyclic enamines has been reported, leading regioselectively to diversely substituted 1,4-DHP derivatives (Scheme 7). The sequence involving such starting materials was performed in numerous efficient systems, and more particularly in the following (1) microwave-assisted reaction in acetic acid [50], DMF [51], or an acetic acid/DMF system [52] (2) sonification in ethylene glycol [53] and (3) use of ionic liquids such as [bmim]BF4 [54]. 

Our own group is also involved in the development of domino multicomponent reactions for the synthesis of heterocycles of both pharmacologic and synthetic interest [156]. In particular, we recently reported a totally regioselective and metal-free Michael addition-initiated three-component substrate directed route to polysubstituted pyridines from 1,3-dicarbonyls. Thus, the direct condensation of 1,3-diketones, (3-ketoesters, or p-ketoamides with a,p-unsaturated aldehydes or ketones with a synthetic equivalent of ammonia, under heterogeneous catalysis by 4 A molecular sieves, provided the desired heterocycles after in situ oxidation (Scheme 56) [157]. A mechanistic study demonstrated that the first step of the sequence was a molecular sieves-promoted Michael addition between the 1,3-dicarbonyl and the cx,p-unsaturated carbonyl compound. The corresponding 1,5-dicarbonyl adduct then reacts with the ammonia source leading to a DHP derivative, which is spontaneously converted to the aromatized product. 

The reaction between an aldehyde and an a-diketone in the presence of an ammonia source is an important route to 1//-imidazoles. When the aldehyde is replaced by a second ketone, a 2//-imidazole is the product (Scheme Optimum yields are obtained by heating with 10 mol am-... 

The synthetic procedure developed by Usyatinsky involves pre-absorbing the mixture of acidic support and ammonium acetate (ammonia source) with an ether solution of the starting materials, evaporating the solvent and heating the solid residue in a domestic microwave oven for 20 min (Scheme 5.21). After irradiation, the reaction mixture was allowed to cool to room temperature and was then washed with a mixture of acetone and triethylamine to extract the product from the solid support. No yields were quoted but the purities of the products were quoted to be 75-85%. 

One primary determinant for atmospheric, hence fogwater, acidity is the relative abundance of ammonia (2). In an ammonia source region such as the SJV, there are factors which can suppress or accelerate NH release. Conditions under which fogwater acidity was low were related to factors favoring ammonia release from sources, such as higher soil moisture and temperatures (6). 

Fulop and co-workers [124] have reported the synthesis of some new (ami-noalkyl) naphthols and (aminoalkyl) quinolinols 85 in good yields through a one-pot, microwave-assisted three-component modified Mannich reaction of naphthol or quinolinol with two equivalents of an aldehyde using ammonium carbamate or ammonium hydrogen carbonate as solid ammonia sources. It was observed that aliphatic aldehydes did not lead to the formation of the desired (aminoalkyl) quinolinols 85 (Scheme 64). 

Szatmari I, Fulop F (2009) Microwave-assisted one-pot synthesis of (aminoalkyl) naphthols and aminoalkyl) quinolinols by using ammonium carbamate or ammonium hydrogen carbonate as solid ammonia source. Synthesis 5 775-778... 

The most direct synthesis of 1,4-dihydropyridines (7b) utilizes a procedure with either <5 + 1>, <3 + 2+1), or <2 + 1 + 2 + (1)> fragment combination. The latter represents the widely used classical Hantzsch s synthesis, which combines two molecules of an active a-methylenic carbonyl compound, an aldehyde, and an ammonia source (Scheme 3). 

Figure 3.8 A schematic of soil injection of anyhdrous ammonia. Source [5].

Figure 3.11 Nitric acid via oxidation of ammonia. Source [3],...

Triazines can be prepared by the condensation of amidrazones with diketones or of hydrazides with 2-halo-ketones. It is convenient to oxidize 2-hydroxy-ketones to the dicarbonyl component with manganese(IV) oxide, in the presence of the amidrazone, to produce the heterocycles. Hydrazides can also be utilized with 1,2-diketones, by including an ammonia source in the reagent mix. ... 

We compared the effect of other ammonia sources to ammonium nitrate. The data are shown in Table 3. Acetonine was the major product on ammonium sulfate and ammonium chloride. When we use ammonia nitrate as the only am-... 

Ammonia Source Weight % Yield Selectivity Side Product ... 

Analysis of effluent gases from nitric acid plants that contain NO, 02, H20, and N2 should not present any problem, and the reaction might also be useful for NO control processes since an ammonia source is normally available in such plants. Analysis capability for ammonia was suggested by the data in Figure 3, and this was confirmed by studies with constant NO addition. 

Many of the reactions producing imidazoles in tobacco and tobacco smoke involve the interaction of carbohydrates with ammonia, which has several precursors in tobacco. Amino acids and proteins can contribute to the formation of smoke amines and the formation of ammonia. Johnson et al. (1964) conclusively demonstrated through experiments with W-glycine that it is an ammonia source. In addition to amino acids, nitrates have been shown to be efficiently converted during the smoking of a cigarette to ammonia (1964). This ammonia from nitrates was shown to participate in the formation of many nitrogenous compounds in smoke. Thus, leaf nitrates as well as amino acids and proteins are considered the major sources of ammonia in tobacco smoke. 

Hantzsch pyridine derivatives 146 were prepared by the reaction of aldehydes and 3-dicarbonyls in the presence of ammonium chlorate at 80 C under solvent-free conditions. Ammonium chlorate was used both as ammonia source and as oxidizing agent source for the direct synthesis and oxidation of Hantzsch 1,4-dihydropyridines to pyridines. 

Until about 1920, coal was the major source of ammonia but the onset of a blossoming petrochemical industry reduced the importance of coal as an ammonia source. However, recent shortages... 

Hydrogen Methane gas Nitrogen Oxygen ammonia recovery Calcium hydroxide ammonia source Ammonium carbonate ammonia testing... 

Natural sources of NO / principally chemical and bacterial denitrification in soil, account for very approximately 50% of NO in the atmosphere. One should also add that ammonia sources (principally fertilisers) also make some contribution to total NOx. 

Addition of an ammonia source to pyrylium salts readily affords pyridine derivatives and provides a good method for the preparation of the pyridine moiety if the corresponding pyrylium salt is accessible. The carbon oxygen double bond present in the pyrylium salt is an oxonium ion however, owing to aromatic stabilization they are easily formed by a variety of methods. The reactivity of pyrylium salts toward nucleophiles makes them useful reagents for the preparation of structurally diverse heterocyclic compounds. Thus pyrylium salts afford pyridines by reaction with ammonia, pyridine-A -oxides by reaction with hydroxylamine and pyridinium salts by reaction with primary amines. 

Fulks G, Fisher G, Rahmoeller K, Wu M, D Herde E, Tan J (2009) A Review of Solid Materials as Alternative Ammonia Sources for Lean NOx Reduction with SCR. SAE Technical Paper 2009-01-0907 Nissinen T, Kukkonen J (2009) US Patent 7595034B2... 

The results from this model, when varying the space velocity, are shown in Fig. 12.20 [38]. In these experiments, urea was used as an ammonia source and the thermal decomposition of urea was conducted at 350 °C in order to completely decompose urea into ammonia and HNCO [39]. 

Air quality research subcommittee. 2000. Atmospheric ammonia Sources and fate. In Air Quality Research Subcommittee Meeting Report, ed. Committee on the environment and natural resources. 

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