Nitrogen synthesis

The source of nitrogen for the synthesis gas has always been air, either supplied directly from a liquid-air separation plant or by burning a small amount of the hydrogen with air in the H2 gas. The need for air separation plants has been eliminated in modern ammonia plants by use of secondary reforming, where residual methane from the primary reformer is adiabatically reformed with sufficient air to produce a 3 1 mole ratio hydrogen-nitrogen synthesis gas. 

Kinetic dependences of the conversion of h-BN into c-BN in the Li-B-N-F system have been studied by introducing about 6% additional nitrogen with addition of nitrogen compounds [170]. The stoichiometry of the c-BN was increased by adding nitrogen (synthesis pressure 4.3 GPa, 1750-1850 K). 

Nitrogen Synthesis of proteins, nucleic Ammonia is toxic at high con- Leaching of nitrogenous fertil-... 

Nitrogen Synthesis of proteins, nucleic acids, etc. Steps in the nitrogen cycle (organic N — NHj —no —NOJ —... 

Pyrolysis of Organic Fluorine Compounds in Thermal Plasma of Nitrogen Synthesis of Nitrogen-Containing Fluorocarbons... 

Ghosh K, Eroy-Reveles AA et al (2004) Reactions of NO with Mn (II) and Mn (III) centers coordinated to carboxamido nitrogen synthesis of a manganese nitrosyl with photolabile NO. Inorg Chem 43 2988-2997... 

Direct synthesis of ammonia from nitrogen and hydrogen was first carried out successfully on a commercial scale in Germany in 1913, Plants were built in several other countries after World War 1, Most of these plants derived their hydrogen-nitrogen synthesis mixtures from the reactions of coke with steam and air. 

During the latter half of the 20th century, successive improvements in ammonia production have lowered-the-cost to the point that its liberal use in crop production is economically attractive. Notable among these improvements was perfection of processes for reforming natural gas or naphtha to supply the hydrogen-nitrogen synthesis gas and to increase the scale of operation. 

Gusev, S.S., Grinshpan, D.D. andKaputskii, RN. (1976) Infrared spectra ofproducts of cellulose oxidation by nitrogen synthesis. Zh. Prikl. Spektrosk., 24, 716-19. 

Ndinguii MW, Fronczek FR, MarzilU PA, Crowe WE, Hammer RP, Marzilli LG (2010) Exploring water-soluble Pt(ll) complexes of diethylenetiiamine derivatives functionalized at the central nitrogen. Synthesis, characterization, and reaction with 5 -GMP. Inorg Chim Acta 363 1796-1804... 

Colostrum produced by the milk glands in the first few days after parturition is rich in protein and minerals. The protein content is particularly rich in immunoglobulins providing anti-infective agents, tryptophan needed for regulating nitrogen synthesis, and arginine which stimulates urea cycle function. 

It must be emphasized that NMR is first and foremost a tool for structural analysis and, in addition to the petroleum analyses described above, the technique (phosphorus NMR and sometimes nitrogen NMR) is abundantly used in all petrochemical synthesis operations. 

You will have noticed that, throughout this chapter, the heteroatom has always been hie nucleophile. There is one way to use nitrogen as an electrophile however and this provides a good synhion for ammo acid synthesis ... 

Analysis Since there is one CH2 group next to the nitrogen atom, this might be a carbonyl group in our usual method of amine synthesis (frame 237). 

Synthesis of Alkviamines. General Procedures. Method (A). The synthesis of p-phenethylamine is representative. A flame dried, nitrogen-flushed, 100 ml flask, equipped with a septum inlet, magnetic stirring bar and reflux condenser ivas cooled to 0°C. Sodium borohydride (9.5 mmol, 0.36 g) was placed in the flask followed by sequential addition of THF (13-15 ml) and BF3-Et20 (12 mmol, 1.5 ml) at 0°C. After the addition, the ice bath was removed and the contents were stirred at room temperature for 15 min. The solution... 

The problem of the synthesis of highly substituted olefins from ketones according to this principle was solved by D.H.R. Barton. The ketones are first connected to azines by hydrazine and secondly treated with hydrogen sulfide to yield 1,3,4-thiadiazolidines. In this heterocycle the substituents of the prospective olefin are too far from each other to produce problems. Mild oxidation of the hydrazine nitrogens produces d -l,3,4-thiadiazolines. The decisive step of carbon-carbon bond formation is achieved in a thermal reaction a nitrogen molecule is cleaved off and the biradical formed recombines immediately since its two reactive centers are hold together by the sulfur atom. The thiirane (episulfide) can be finally desulfurized by phosphines or phosphites, and the desired olefin is formed. With very large substituents the 1,3,4-thiadiazolidines do not form with hydrazine. In such cases, however, direct thiadiazoline formation from thiones and diazo compounds is often possible, or a thermal reaction between alkylideneazinophosphoranes and thiones may be successful (D.H.R. Barton, 1972, 1974, 1975). 

Low-valent nitrogen and phosphorus compounds are used to remove hetero atoms from organic compounds. Important examples are the Wolff-Kishner type reduction of ketones to hydrocarbons (R.L. Augustine, 1968 D. Todd, 1948 R.O. Hutchins, 1973B) and Barton s olefin synthesis (p. 35) both using hydrazine derivatives. 

A completely different, important type of synthesis, which was developed more recently, takes advantage of the electrophilicity of nitrogen-containing 1,3-dipolar compounds rather than the nucleophilicity of amines or enamines. Such compounds add to multiple bonds, e.g. C—C, C C, C—O, in a [2 + 3 -cycioaddition to form five-membered heterocycles. 

In spite of the diverse nature of alkaloid structures, two structural units, i.e. fused pyrrolidine and piperidine rings in different oxidation states, appear as rather common denominators. We therefore chose to give several examples for four types of synthetic reactions which have frequently been used in alkaloid total synthesis and which provide generally useful routes to polycyclic compounds with five- or six-membered rings containing one nitrogen atom. These are ... 

The Diels-Alder reaction of o-quinodimethanes (from benzocyclobutenes) with nitrogen-ubstituted enes has also been applied to alkaloids synthesis (see p. 280f. T. Kametani, 1972, 1973, 1974 W. Oppolzer, 1978 A). 

The nucleophilicity of amine nitrogens is also differentiated by their environments. In 2,4,5,6-tetraaminopyrimidine the most basic 3-amino group can be selectively converted to a Schiff base. It is meta to both pyrimidine nitrogens and does not form a tautomeric imine as do the ortho- and /xira-amino groups. This factor is the basis of the commercial synthesis of triamterene. 

Other interesting regioselective reactions are carried out within the synthesis of nitrofurantoin. Benzaidehyde semicarbazone substitutes chlorine in chloroacetic ester with the most nucleophilic hydrazone nitrogen atom. Transamidation of the ester occurs with the di-protic outer nitrogen atom. Only one nucleophilic nitrogen atom remains in the cyclization product and reacts exclusively with carbonyl compounds. 

Two synthetic bridged nitrogen heterocycles are also prepared on a commercial scale. The pentazocine synthesis consists of a reductive alkylation of a pyridinium ring, a remarkable and puzzling addition to the most hindered position, hydrogenation of an enamine, and acid-catalyzed substitution of a phenol derivative. The synthesis is an application of the reactivity rules discussed in the alkaloid section. The same applies for clidinium bromide. 

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