Amines, purification

Note that the methanation section is the last processing step in the HYGAS pilot plant, and it depends on the steady-state troublefree operation of the preceding steps (the gasification reactor, amine purification, and caustic wash sections for cleanup sulfur removal) before it can be brought on-line. 

Preparative Methods the phosphoramidite ligand can be prepared by the nucleophilic substitution of phosphory 1 chloride (formed from the reaction of PCI3 and (S)-2,2 -binaphthol in presence of triethylamine) with (R,R)-bis(l-phenylethyl)amine. Purification recrystallization from diethyl ether/dichloro-methane. 

In short the chemistry and properties of the inorganic lithium chelates should promote their uses in many applications. This is the case for the N-chelated organolithium reagents, as evidenced by the frequency of appearance of these systems in the literature. We hope that the poly-amine-purification technique presented here will improve the availability of useful chelating ligands and stimulate additional research in this area. 

Since part of the product may remain in solution as the lithium thiolate or alcoholate, it is advisable to carry out the hydrolysis of the reaction mixtures in the presence of an equivalent amount of mineral acid. If the metallated hetero-aromatic compound has been obtained via lithiation with LDA, or with BuLi TMEDA, an additional amount of acid is required to neutralize the amine. Purification in many cases can be carried out by crystallization from an organic solvent. 

Mitsukura, K Kuramoto, T Yoshida, T, Kimoto, N Yamamoto, H and Nagasawa, T. (2013) A NADPH-dependent (S)-imine reductase (SIR) from Streptomyces sp. GF3546 for asymmetric synthesis of optically active amines purification, characterization, gene cloning, and expression. Appl. Microbiol. Bioteclmol.l0.1007/s00253-012-4629-4... 

The discovery of an antirhinoviral lead from a library of 4000 ureas was disclosed by Kaldor and coworkers [11]. Pools of 10 compounds were prepared by reaction of excess isocyanate with an equimolar mixture of 10 amines. Purification was effected by addition of aminomethylpolystyrene to remove isocyanate impurities followed by filtration and evaporation (Figure 4). 

The general theory behind the process is that the hypohalite will convert the amide to a haloamide. This then spontaneously changes to the isocyanate when heated and decomposes to the amine from the water present. In effect, all that happens is that a Carbonyl (CO) group is stripped off the starting amide to yield the corresponding amine. Yields pre- purification are around 80%, post-purification average around 65%. Certain uses of the result-... 

Manufacture and Uses. Acetoacetic esters are generally made from diketene and the corresponding alcohol as a solvent ia the presence of a catalyst. In the case of Hquid alcohols, manufacturiag is carried out by continuous reaction ia a tubular reactor with carefully adjusted feeds of diketene, alcohol, and catalyst, or alcohol—catalyst blend followed by continuous purification (Fig. 3). For soHd alcohols, an iaert solvent is used. Catalysts used iaclude strong acids, tertiary amines, salts such as sodium acetate [127-09-3], organophosphoms compounds, and organometaHic compounds (5). 

Many mercury compounds are labile and easily decomposed by light, heat, and reducing agents. In the presence of organic compounds of weak reducing activity, such as amines (qv), aldehydes (qv), and ketones (qv), compounds of lower oxidation state and mercury metal are often formed. Only a few mercury compounds, eg, mercuric bromide/77< 5 7-/7, mercurous chloride, mercuric s A ide[1344-48-5] and mercurous iodide [15385-57-6] are volatile and capable of purification by sublimation. This innate lack of stabiUty in mercury compounds makes the recovery of mercury from various wastes that accumulate with the production of compounds of economic and commercial importance relatively easy (see Recycling). 

Many aminonaphthalenesulfonic acids are important in the manufacture of azo dyes (qv) or are used to make intermediates for azo acid dyes, direct, and fiber-reactive dyes (see Dyes, reactive). Usually, the aminonaphthalenesulfonic acids are made by either the sulfonation of naphthalenamines, the nitration—reduction of naphthalenesulfonic acids, the Bucherer-type amination of naphtholsulfonic acids, or the desulfonation of an aminonaphthalenedi-or ttisulfonic acid. Most of these processes produce by-products or mixtures which often are separated in subsequent purification steps. A summary of commercially important aminonaphthalenesulfonic acids is given in Table 4. 

Modem commercial wet-acid purification processes (see Fig. 4) are based on solvents such as C to Cg alcohols, ethers, ketones, amines, and phosphate esters (10—12). Organic-phase extraction of phosphoric acid is accompHshed in one or more extraction columns or, less frequently, in a series of countercurrent mixer—settlers. Generally, 60—75% of the feed acid P2 s content is extracted into the organic phase as H PO. The residual phosphoric acid phase (raffinate), containing 25—40% of the original P2O5 value, is typically used for fertilizer manufacture such as triple superphosphate. For this reason, wet-acid purification units are almost always located within or next to fertilizer complexes. 

Trickle bed reaction of diol (12) using amine solvents (41) has been found effective for producing PDCHA, and heavy hydrocarbon codistiUation may be used to enhance diamine purification from contaminant monoamines (42). Continuous flow amination of the cycloaUphatic diol in a Hquid ammonia mixed feed gives >90% yields of cycloaUphatic diamine over reduced Co /Ni/Cu catalyst on phosphoric acid-treated alumina at 220°C with to yield a system pressure of 30 MPa (4350 psi) (43). 

The N-oxide function has proved useful for the activation of the pyridine ring, directed toward both nucleophilic and electrophilic attack (see Amine oxides). However, pyridine N-oxides have not been used widely ia iadustrial practice, because reactions involving them almost iavariably produce at least some isomeric by-products, a dding to the cost of purification of the desired isomer. Frequently, attack takes place first at the O-substituent, with subsequent rearrangement iato the ring. For example, 3-picoline N-oxide [1003-73-2] (40) reacts with acetic anhydride to give a mixture of pyridone products ia equal amounts, 5-methyl-2-pyridone [1003-68-5] and 3-methyl-2-pyridone [1003-56-1] (11). 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

If the material is not partly dried before hydrolysis, the yield of the hydrochloride is diminished because of its solubility. If pure 3-bromo-4-acetaminotoluene is desired, the crude material may be crystallized from 50 per cent alcohol with the addition of decolorizing carbon (Norite) as almost colorless needles, m.p. 116-117°, The yield is 360 g, (79 per cent of the theoretical amount). This purification has no advantage when the acetam-ino compound is to be hydrolyzed to the amine. 

Dimethylfarmamlde and triethyl amine were purchased from Baker (Baker Analyzed Reagent) and used without further purification. 

Purification as their N-acetyl derivatives is satisfactory for primary, and to a limited extent secondary, amines. The base is refluxed with slightly more than one equivalent of acetic anhydride for half to one hour, cooled and poured into ice-cold water. The insoluble derivative is filtered off, dried, and recrystallised from water, ethanol, aqueous ethanol or benzene (CAUTION toxic ). The derivative can be hydrolysed to the parent amine by refluxing with 70% sulfuric acid for a half to one hour. The solution is cooled, poured onto ice, and made alkaline. The amine is steam distilled or extracted as above. Alkaline hydrolysis is very slow. 

Rapid purification Stir over CaH2 (5% w/v) overnight, filter, then distil at 20mmHg. Store the distd DMF over 3A or 4A molecular sieves. For solid phase synthesis, the DMF used must be of high quality and free from amines. 

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