Amines processing

Experience in air separation plant operations and other ciyogenic processing plants has shown that local freeze-out of impurities such as carbon dioxide can occur at concentrations well below the solubihty limit. For this reason, the carbon dioxide content of the feed gas sub-jec t to the minimum operating temperature is usually kept below 50 ppm. The amine process and the molecular sieve adsorption process are the most widely used methods for carbon dioxide removal. The amine process involves adsorption of the impurity by a lean aqueous organic amine solution. With sufficient amine recirculation rate, the carbon dioxide in the treated gas can be reduced to less than 25 ppm. Oxygen is removed by a catalytic reaction with hydrogen to form water. 

In an indirect amination process, acyl halides are converted to amino acids. Reaction of the acyl halide with a chiral oxazolidinone leads to a chiral amide, which reacts with the N=N unit of a dialkyl azodicarboxylate [R"02C—N=N—CO2R ]. Hydrolysis and catalytic hydrogenation leads to an amino acid with good enantioselectivity. ... 

An enantioselective synthesis of (—)-lupinine 6 was based on a similar reductive amination process. In this case, (k)-phcnylglycinol was used to obtain a chiral nonracemic oxazololactam which was cyclized after reduction of N-C and O-C bonds and subsequent hydrolysis of the masked aldehyde <2004T5433>. 

Aldehyde groups can be converted into terminal amines by a reductive amination process with ammonia or a diamine compound. The reaction proceeds by initial formation of a Schiff base... 

Figure 1.124 Aldehyde groups may be blocked with Tris or ethanolamine using a reductive amination process.

Aldehyde particles are spontaneously reactive with hydrazine or hydrazide derivatives, forming hydrazone linkages upon Schiff base formation. Reactions with amine-containing molecules, such as proteins, can be done through a reductive amination process using sodium cyanoborohydride (Figure 14.21). 

Isik M, Sponza DT (2003) Effect of oxygen on decolorization of azo dyes by Escherichia coli and Pseudomonas sp. and fate of aromatic amines. Process Biochem 38 1183-1192... 

Rhodium-catalyzed oxidative C arylations of unprotected pyrroles have been reported, and the products were the result of both arylation and amination processes (Equation (28)).37... 

An ingenious strategy developed by Jun s group makes use of a chelating 3-picolin-2-yl group for performing C-C bond forming reactions. In the particular example shown, for the synthesis of aromatic ketones, methylvinyl ketone is added to suppress unwanted reductive amination processes (Equation (130)). 

The transition metal-catalyzed C-H insertion reaction of carbenes to organic compounds is a well-established synthetic method, as shown in the first two sections in this chapter. However, nitrene C-H insertion, the corresponding reaction of carbene analog, is much less known. In the past decade, considerable advances have been made in the development of this chemistry into a generally useful C-H amination process by using improved catalysts and protocols, in which readily available amines or amides are used as the starting substrates. Moreover,... 

Alkanolamines, generally referred to as amines, are organic compounds of the form Hn-N-(R0H)3-n (3) the hydroxyl group generally provides for the compounds solubility in water, while the HN group provides the alkalinity in water solutions to cause the absorption of acid gases. Amine processes used commercially are shown in Table I. These compounds are chemical solvents they combine chemically with H2S, C02, and other sulfur compounds. They are customarily regenerated by the application of heat. 

Reaction 38 shows that hydroxylamines can cause amination at allylic positions. Fe(II) phthalocyanine (222c) was the most effective catalyst. Other catalysts and substrates were also investigated623. Complexes of Mo(VI) were less effective than 222c as catalysts for amination processes of this type624. 

An important consequence of these results is that the overall amination process (37 to 39 ), which at first sight seems to follow a classical Sn(AE) pathway, is thus in fact a meta telesubstitution. This aminodehalogenation is one of the few reactions known that has proved to involve an Sn (ANRORC) mechanism, but that cannot be described as a degenerate ring... 

This author and coworkers at Beckman Coulter first described the use of a low form 96-well plastic microplate for automated micro-ELISA immunoassays (Matson et al., 2001). The polypropylene plate was first modified by a radiofrequency plasma amination process (Matson et al., 1995) followed by conversion to an acyl fluoride surface chemistry for rapid covalent attachment of biomolecules. Proteins (1 to 2 mg/mL) were prepared in 50 mM carbonate buffer, pH 9, containing 4% sodium sulfate (to improve spot uniformity) and printed using a conventional arrayer system. Approximately 200-pL droplets of monoclonal antibodies (anti-cytokine) were deposited into the bottom of the microwells using a Cartesian PS7200 system equipped... 

Preliminary efforts to examine the mechanism of C-H amination proved inconclusive with respect to the intermediacy of carbamoyl iminoiodinane 12. Control experiments in which carbamate 11 and PhI(OAc)2 were heated in CD2CI2 at 40°C with and without MgO gave no indication of a reaction between substrate and oxidant by NMR. In Hne with these observations, synthesis of a carbamate-derived iodinane has remained elusive. The inability to prepare iminoiodinane reagents from carbamate esters precluded their evaluation in catalytic nitrene transfer chemistry. By employing the PhI(OAc)2/MgO conditions, however, 1° carbamates can now serve as effective N-atom sources. The synthetic scope of metal-catalyzed C-H amination processes is thus expanded considerably as a result of this invention. Details of the reaction mechanism for this rhodium-mediated intramolecular oxidation are presented in Section 17.8. 

The electrophilic amination reaction of organometallic species using mono-, di- and trihaloamines has attracted a lot of attention for the synthesis of amines. Only a few cases have been reported using alkylchloroamines as precursors for the synthesis of tertiary amines One example is the reaction of functionalized aryhnagnesium compounds with benzyl-V-chloroamines 252 providing polyfunctional tertiary amines 253 (equation 164) °. The procedure was also applied for the preparation of chiral V-chloro-amines with retention of chirahty at the a-carbon. However, the amination process is limited to benzyl-V-chloroamines. 

Alkanolamines. Gas sweetening, ie, removal of hydrogen sulfide and carbon dioxide, using alkanolamines was patented in 1930. Several amine solvents are available as of the mid-1990s. The most widely used are monoethanolamine [141-43-5], diethanolamine [111-42-2], diglycolamine [929-06-6], and methyldiethanolamine [105-59-9]. Amine processes are generally applicable when hydrogen sulfide concentration in the feed gas is relatively low (eg,... 

In an indirect amination process, acyl halides are enantioselectively converted to amino acids.176 The key step involves addition to the N=N bond of a dialkyl azodicarboxylate 22. 

Aliphatic Isocyanates. Conventional aliphatic isocyanates have historically been manufactured using the hydrogen chloride salt slurry approach. Exceptions to this arc the longer chain aliphalics which, due to the increased solubility, have reaction rates conductive in the Tree amine process. An alternative approach, generally referred to as a two-phase phosgenation, has gained wide scale acceptance for the production of aliphatic isocyanates. 

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