Physical properties aliphatic amines

Amine oxides, known as A[-oxides of tertiary amines, are classified as aromatic or aliphatic, depending on whether the nitrogen is part of an aromatic ring system or not. This stmctural difference accounts for the difference in chemical and physical properties between the two types. 

Acetyltransferases catalyze the acetylation of amino, hydroxyl, and thiol functional groups. Acetylation of hydroxy and thiol groups is comparatively rare and of much less importance in alkaloid metabolism than reactions with amino functional groups. The types of amines that are acetylated include arylamines (the major route of metabolism in many species), aliphatic amines, hydrazines, sulfonamides, and the a-amino group of cysteine conjugates. The purification, physical properties, and specificity of the N-acetyltransfereases have been reviewed (116-118). 

Aliphatic aldehydes, 13 571 physical properties of, 2 60t syntheses of, 12 187 Aliphatic a-hydroxy acids, 14 130 Aliphatic amine/polysulfide co-curing agent systems, 10 410... 

Four types of organic amines exist, as shown in Table 4.8 primary amines RNHj, secondary R2NH2, tertiary RsNH, and quaternary R4N (Appendix D). The hydrocarbon chain R is usually of length Cg-Cu, commonly a straight aliphatic chain, but branched chains and aromatic parts also occur. In general the amines extract metal complexes in the order tertiary > secondary > primary. Only long-chain tertiary and—to a smaller extent—quarternary amines are used in industrial extraction, because of their suitable physical properties trioctylam-ine (TOA, 8 carbons per chain) and trilauryl amine (TLA, 12 carbons per chain) are the most frequently used. For simplicity we abbreviate all amines by RN, and their salts by RNH L . 

We have found similar results with other isocyanates, that is, they react with moisture to form the amines which react with isocyanates and build molecular weight. SFC provides a quick check on this process. Furthermore, films crosslinked with a virgin HDI and one crosslinked with an aged material will exhibit very different physical properties. This example shows the utility of SFC for aliphatic isocyanates, but aromatics isocyanates can also be characterized using SFC (2). 

There have been many attempts to define solvent behavior in terms of one or more physical properties of the solvent, and not without some degree of success. However, it is essential to note that the properties of the coal also play an important role in defining behavior of a solvent, and it has been reported that the relative solvent powers of two solvents may be reversed from one coal type to another. Thus, two properties that have found some relevance in defining solvent behavior with coal (as well as with other complex carbonaceous materials, such as petroleum asphaltenes) are the surface tension and the internal pressure (Speight, 1994, p. 201). However, the solvent power of primary aliphatic amines (and similar compounds) for the lower-rank coals has been attributed to the presence of an unshared pair of electrons (on the nitrogen atom). 

The epoxy product cured with BF3-MEA is densely crosslinked and has excellent physical properties at high temperatures (150 to 175°C). When reacted with an unmodified epoxy resin, the resulting product is very hard and brittle. The chemical resistance, however, is only fair and somewhat less than that of epoxies that are cured with aliphatic amines. 

Aromatic amines. These include materials such as 4,4 -meth-ylenedianiline, m-phenylenediamine, and 4,4 -diamlnodiphenyl-sulfone. Aromatic amines are less reactive than aliphatic amines and usually require curing temperatures as high as 300 °F. Thus, they offer systems that have a long pot life at room temperature and cure to products with excellent physical and chemical property retention up to 300 F. 

These are widely used because the curing of the epoxies takes place at room temperature. High exothermic temperatures develop during the curing reaction that limit the mass of material that can be cured. The electrical and physical properties of these aliphatic-cured resins had the greatest tendency toward degradation of electrical and physical properties at elevated temperatures. Typical aliphatic amines used include diethylene triamine (DETA) and triethylene tetramine (TETA). 

Compared with aliphatic amine cures, the pot life of anhydride cures is usually long and exotherm is low. Elevated-temperature cures at up to 200°C are necessary and long post-cures are required to develop ultimate properties. Electrical and physical strength properties are good over a wide temperature range. Compared with amine-cured systems, anhydride cures offer better chemical resistance to aqueous acids, and less chemical resistance to some reagents. 

Tables 10.2 and 10.3 lists the physical properties of the aliphatic amines. The lowest molecular weight amine, ethylamine, boils at only 16.6 C and is thus available only as a compressed gas or as an aqueous solution. The other fifteen aliphatic amines have boiling points in the range of 32.4-213 C. The flash points of these amines are low with the highest being only 70 F for the tributylamine. These short-chain amines are readily soluble in water and most organic solvents. The solubility of amines decreases with increasing temperature, for example, triethylamine is completely soluble in water below 18 C but is only partially soluble above this temperature. The lower alkylamines have the characteristic ammonia odor which decreases with increased substitution onto the nitrogen atom.

This comprehensive reference book examines the physical and chemical properties, uses, and toxicity of organic solvents in the chemical and related process industries. It will afford the chemist, chemical engineer, researchers, and other workers in the chemical and allied industries the opportunity to review all the important chemical and physical properties of industrial solvents. The current environmental impact of recommended safe handling procedures and chemical reactivity solvents are also presented. The solvents are classified according to their chemical structure and include aldehydes, aliphatic and aromatic hydrocarbons, ethers, halogenated hydrocarbons, ketones, nitroparaffins, and monohydric and polyhydric alcohols. Also covered are acids, aliphatic and heterocyclic amines, esters, glycol ethers, and several miscellaneous solvents. 

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