Other Aromatic Amines

Aromatic Amine Eutectics. There are several curing agents available that consist of eutectics of various aromatic amines. These perform very much as MPDA and MDA do. However, the eutectics are liquids with viscosity of approximately 2000 cP at room temperature. They are readily miscible with liquid epoxy resins at room temperature. 

The aromatic amine eutectics may crystallize on storage. They can be reliquefied by heating to 40°C with stirring. This liquefaction can be accomplished without sacrificing either the curing properties or the final physical and chemical properties of the cured resins. 

Solvent Solutions. Certain solvent solutions of aromatic amines have been noticed to polymerize epoxy resins at room temperature.11 The effect of the solvent is probably to allow sufficient mobility of the polymer chains for an adequate degree of crosslinking to occur before the viscosity becomes so high that the molecules are immobilized. The aromatic amine solutions are usually used with a cure accelerator to achieve practical cure rates at room temperature. 

However, the incorporation of the solvent in the cured resin will significantly lower the glass transition temperature and thermal resistance. When cured at room temperatures, these solutions give properties more similar to those of the polyamide curing agents, but they do have the advantage of low viscosity and adjustable cure rate. 

DADS melts at 135°C and is employed stoichiometrically with DGEBA at 33.5 pph. Fortunately, it is relatively unreactive so it can be mixed with epoxy resin at elevated temperatures. It can also be used in epoxy solutions to provide an adhesive formulation for manufacturing supported or unsupported film with long shelf life. Because of the low reactivity of the system, DADS is generally employed at a concentration that is about 10 percent greater than stoichiometry, or an accelerator, such as BF3-MEA, is employed at about 0.5 to 2 pph. When DADS is mixed with liquid DGEBA resin, it provides a pot life of 3 h at 100°C and requires a rather extended high-temperature cure to achieve optimal physical properties. 

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Although aminyl radicals are stable towards oxygen, they can oxidi2e other aromatic amines, phenols and thiols (10), and regenerate the diarylamine. Thus, mixtures of phenols and diarylamines frequendy show better antioxidant activity than either one alone. This is called synergism. 

MDA reacts similarly to other aromatic amines under the proper conditions. For example, nitration, bromination, acetylation, and dia2oti2ation (1 3) all give the expected products. Much of the chemistry carried out on MDA takes advantage of the diftmctionality of the molecule in reacting with multiftmctional substrates to produce low and high molecular weight polymers. 

Aniline and other aromatic amines are valuable industrial raw materials. They form an important starting point from which many of our dyestuffs, medicinals, and other valuable products are prepared. For example, you have used the indicator, methyl orange, in your laboratory experiments. Methyl orange is an example of an anQine-derived dye, although it is used more as an acid-base indicator than for dyeing fabrics. The structure of methyl orange is as follows ... 

On increasing the acidity still further (>0.1 m H2S04, i.e., H0< 1), the rate of diazotization of aniline passes through a minimum and then increases rapidly (region B in Fig. 3-1). The plot in Figure 3-1 is a somewhat schematic representation of the minimum, the position of which depends very much on the concentration of nitrous acid. Moreover, with other aromatic amines the plot is not exactly the same, but it can be explained by analogous arguments. 

The formation of a bis(guanidinate)-supported titanium imido complex has been achieved in different ways, two of which are illustrated in Scheme 90. The product is an effective catalyst for the hydroamination of alkynes (cf. Section V.B). It also undergoes clean exchange reactions with other aromatic amines to afford new imide complexes such as [Me2NC(NPr )2]2Ti = NC6F5. ... 

Note Other aromatic amines, e. g. 1- or 2-naphthylamine in acetic acid solution (Griess reagent), can be used as coupling agent instead of N-(l-naphthyl)-ethylenediamine ... 

In the previous analysis for the second quadrant amines, there was evidence that the presence of an aromatic ring (BzAM) increased competition with the deactivating intermediate(s) and significantly the amount of DHQ obtained. The study was thus extended to other aromatic amines aniline (AN), 2-ethylaniline (2-ETAN), 3-ethylaniline (3-ETAN) and N-ethylaniline (N-ETAN). These amines are not classified in the literature analysis of amine properties (16), although aniline and pyridine were studied by statistical analysis of their solvent properties and classified in the same sector (16). By analogy, we hypothesize that these model aromatic amines should be classified in the second sector. Thus, they may aid in an understanding of the specific role of the aromatic ring and the effect of an alkyl substituent. 

Aluminum chloride-phosphorus oxychloride complex, 31, 88 Amberlite IR-4B resin, 32, 13 Amidation, of isocyanic acid with bromo-aniline and other aromatic amines, 31,8... 

Historically, bladder tumors have been associated with exposures in the aniline dye industry. However, conclusive evidence for any one particular exposure could not be obtained in these studies since the workers were exposed to many chemicals within the same work area. For example, Case et al. (1954) investigated the incidence of bladder tumors among British workers in the chemical dye industry. In addition to aniline, the workers were exposed to other aromatic amines, including a- and P-naphthylamine, benzidine, and auramine. Although exposures could not be quantified, there was insufficient evidence to suggest that aniline was a cause of bladder cancers. More recent studies indicate that P-naphthylamine, 4-aminodiphenyl, 4-nitrodiphenyl, 4,4-diaminodiphenyl, or o-toluidine may be involved in increased cancers in the dye industry (Ward et al. 1991 Benya and Cornish 1994). 

Baird, R., Carmona, L., and Jenkins, R.L. Behavior of benzidine and other aromatic amines in aerobic wastewater treatment, J. Water Pollut. Control Fed, A9(1) IG09-1615, 1977. 

A vapor pressure of 4.5><10 mm Hg at 20 °C has been reported (DCMA 1989). Prior to OSHA 1974 regulations, benzidine and 3,3 -dichlorobenzidine were manufactured in open systems that permitted atmospheric releases of suspended particles at the work site (Shriner et al. 1978), but no historical data were located specifically for 3,3 -dichlorobenzidine emissions (atmospheric or in water). The absence of data may be attributed to analytical methods used at that time that could not distinguish benzidine from its derivatives or many other aromatic amines (Shriner et al. 1978). Under OSHA regulations adopted in 1974, only closed manufacturing systems are permitted, and atmospheric emissions are presumably reduced because of this regulation. 

Aniline is a simple aromatic compound composed of an amino group attached to a benzene ring. Other aromatic amines are aniline derivatives. Some examples of aromatic amines are shown in Figure 13-2. 

Adapted from Cheever et al. (1980) Son et al. (1980) KuUcami et al. (1983) and Gupta et al. (1987) Brackets indicate postulated proximate or reactive metabolites of ort/zo-toluidine, based on data from the metabolism of other aromatic amines. 

Like other aromatic amines 4-chloro-ort/20-toluidine has been shown to undergo metabolic activation resulting in covalent binding to tissue proteins, DNA and RNA both in vivo and in vitro (Hill et al., 1979 Bentley et al., 1986a,b Bimer Neumann, 1988). 

Chloro-ort/70-toluidine undergoes extensive metabolism in rodents in vivo. Like other aromatic amines, it undergoes metabolic activation via initial formation of the 7V-hydroxy derivative. The further metabolic processing of this metabolite has not been investigated. 

Like other aromatic amines, 5-chloro-ori/20-toluidine undergoes an initial metabolic activation step, probably A-oxidation, to form a nitrosoarene that can bind covalently to haemoglobin. 

The high-temperature reaction of aromatic amines with aromatic nitro compounds in the presence of base affords primarily an azo compound [39,40]. Because two independent laboratories have reported reasonable results with this synthesis, the procedure is given here. To be noted is that, while the reaction as described here involves 2-naphthylamine, a known carcinogenic intermediate, it is given only for reference to the procedure. Evidently, other aromatic amines also undergo the reaction. 

Other aromatic amines, (I), and perfluoropolyaromatic amines, (II), were previously prepared by the authors (1,2), respectively, and were used in hole transport layers. 

Some other aromatic amines such as benzidine and 4-aminobiphenyl are also carcinogenic to the bladder by the same mechanism. These amines have industrial uses and have been implicated in bladder cancer in exposed humans. 

Both NAT1 and NAT2 N-acetylate benzidine and O-acetylate the N-hydroxy metabolite. Because NAT2 and, to a lesser extent, NAT1 both show variation in the human population, this influences susceptibility to the carcinogenic effects of arylamines such as benzidine. With other aromatic amines, such as the heterocyclic amines found as food pyrolysis degradation products, N-acetylation is not favored, N-oxidation being the primary route followed by O-acetylation. This seems to take place in the colon. 

Similar results are obtained with other aromatic amines such as aniline and />-iodoaniline yielding mercury diphenyl and mercury di-/>-iodopheny]. 

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