Purification, general amines

A problem in the use of many amines as pH buffers is that they are liquids or gases at room temperature and are difficult to obtain pure. Of the solid amines, 4-amino-pyridine, imidazole and Tris are ordinarily available in acceptable purity, but others, such as 2-amino-2-methyl-1,3-propanediol, 2-amino-2-methyl-l-propanol and hexa-methylenediamine, may need further purification, commonly by distillation. However it is difficult to remove residual monoethanolamine and diethanolamine from triethanolamine. A general method for the purification of amines is through the preparation of their hydrochlorides. 

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). 

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. 

The method described is rather general. With appropriate modifications for the purification of the aim ne the method yields a- -tolylethylamine (72 per cent), a-p-chlorophenylethyl-amine (65 per cent), a -/)-bromophenylethylamine (63 per cent), a- -xenylethylamine (66 per cent), and a-(/9-naphthyl)-ethylamine (84 per cent) from the corresponding ketones. 

The following are some of the typical industrial applications for liquid-phase carbon adsorption. Generally liquid-phase carbon adsorbents are used to decolorize or purify liquids, solutions, and liquefiable materials such as waxes. Specific industrial applications include the decolorization of sugar syrups the removal of sulfurous, phenolic, and hydrocarbon contaminants from wastewater the purification of various aqueous solutions of acids, alkalies, amines, glycols, salts, gelatin, vinegar, fruit juices, pectin, glycerol, and alcoholic spirits dechlorination the removal of... 

N -Ethyl-jK-toluidine has been obtained by passing m-toluidine and ethyl alcohol over a catalyst at high temperatures,1 and by the use of ethyl />-toluenesulfonate 2 as an alkylating agent. The present method of purification is a modification of a general procedure for secondary amines developed by Diepolder.3... 

The alkanephosphonic acid dichlorides obtained by these methods are converted with amines, with all reactions carried out in solvents such as acetone, benzene, or diethyl ether at 10°C with triethylamine as HC1 captor. The conversion runs quantitatively followed by a purification with the help of column chromatography with chloroform/methanol in a ratio of 9 1 as mobile phase. The alkanephosphonic acid bisdiethanolamides could be obtained as pure substances with alkane residues of C8, C10, C12, and Ci4. The N-(2-hydroxyethane) alkanephosphonic acid 0,0-diethanolamide esters were also prepared in high purity. The obtained surfactants are generally stable up to 100°C. Only the alkanephosphonic acid bismonomethylamides are decomposed beneath this temperature forming cyclic compounds. 

Simple substances, and in particular those which are also readily volatile, such as hydrocarbons, alcohols, esters, the lower acids and amines, are distilled under atmospheric pressure. All substances which decompose easily, and those which have especially high boiling points, are distilled under reduced pressure. In general solid substances should only be distilled when purification by crystallisation has been unsuccessful on account of too great solubility or for other reasons. Naturally in each case the possibility of distillation (without decomposition) must be established in advance. 

Several analytical techniques including capillary electrophoresis, thin layer chromatography (TLC), GC, lEC, and HPLC, have been proposed for the determination of biogenic amines in various foods. Among these, RP-HPLC is considered the most suitable one. HPLC methods used for amine determination usually involve two steps amine extraction from the matrix and analytical determination. Depending on the complexity of food matrix and the selectivity of the final analytical determination, a further purification step may be necessary prior to the analytical determination. To ensure adequate sensitivity, a derivatization step is generally required before injection [282]. 

Treatment of tertiary benzylamines with acylating agents can lead to debenzylation. If the benzyl group is linked to an insoluble polymer, acylation and debenzylation will lead to the release of an acylated amine into solution (Entry 6, Table 3.9). These cleavage reactions generally yield products that are contaminated with acylating agent and so require further purification. 

General Procedure for Preparation of Triazones 5a-f. 264 mg (3 mmol) /V,/V-di-metliylurea, 1 g paraformaldehyde, 3 mmol primary amine 4a-f and 2 g montmorillonite K-10 were irradiated by microwave in a Teflon vessel. The reaction mixture was filtered and washed with water. The organic phase was separated and dried with Na2S04 and concentrated by vacuum distillation. Purification of the... 

Application of halogenides under the same conditions results inMHal/OR), which does not decompose in excess of M OR or under refluxing. The patent [833] describes the general method of preparation of the stable metal alkoxide solutions (which are used in technology) it comprises a heterogeneous reaction of Zn, Cd, Y, Ln, In, Pb, Sn, Zr, Sb, Bi and Mn carboxylates in alcohol solutions with NH3 or amines with subsequent purification by ionic exchange. 

The three-step procedure described here illustrates a convenient, general route to di-tert-alkylamines. Extensive purification or isolation of intermediates is not required. The reactions are easily monitored. Only in the final step is the exclusion of air and moisture necessary. It should be noted that tert-butyl-tert-octylamine is considerably more hindered than 2,2,6,6-tetramethylpiperidine. tert-Butyl-tert-octylamine is inert to methyl iodide, while 2,2,6,6-tetramethylpiperidine gives a white precipitate of the pentamethylammonium iodide within minutes upon treatment with methyl iodide at room temperature. The extreme hindrance of this amine has been exploited in the selective deprotonation of carbon adds and in other reactions.10... 

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