Effects Of Aromatic Amines Research Articles

Effect of Aromatic Amines on the Properties of Formaldehyde-Based Xerogels.

This study investigates the synthesis of formaldehyde-based xerogels using alternative aromatic precursors, with comparison to traditional resorcinol-formaldehyde analogues, in order to alter the chemical composition of the resulting gels. By replacing resorcinol with aromatic amine molecules, i.e., ammeline, melamine and melem, each expected to undergo similar reactions with formaldehyde as the substituted species, we found that for all substituted gels, at low additive contents, the gel structure was compromised and non-porous materials were formed, as opposed to the most abundant monomers, and therefore, these additives seem to act as impurities at low levels. Working towards higher additive contents, melem monomers exhibited low solubility (~5%), even at elevated temperatures, thereby limiting the range to which melem could act as a substitute, while melamine could be incorporated up to ~40% under acidic conditions, with enhanced microporosity over this range. Pure gels were successfully synthesised from ammeline, but their performance was inferior to resorcinol-formaldehyde gels, while melamine-formaldehyde analogues required acidic reaction conditions but shrank considerably on sub-critical drying, adversely affecting the gel properties and demonstrating their lack of potential as sorbents. This demonstrates the potential for the inclusion of aminated aromatics within resorcinol-based gel systems, however, only as partial substitutes and not complete replacements.

The effect of aromatic amines and phenols in the thiyl-induced reactions of polyunsaturated fatty acids

Thiols are well known for their role in cellular redox homeostasis, while aromatic amines and phenols are the best known classes of chain-breaking antioxidants. On the other hand, thiyl radicals are known to catalyse the double bond isomerization in PUFA. We investigated the role and interplay of 2-mercaptoethanol and diphenylamine in the parallel processes of peroxidation and cis–trans isomerization of linoleic acid (LA) during gamma radiolysis, both in solution and micelles. Both compounds, used alone were able to protect LA from oxidation; however pro-oxidant activity and enhanced isomerization was observed when they were used together, depending on the experimental settings. Instead, α-tocopherol protected LA from both oxidation and isomerization in the presence of thiols under any tested settings. The mechanistic scenario is discussed highlighting the role of diphenylaminyl radicals in promoting thiyl-radical-induced cis–trans isomerization in the presence of oxygen.

The effect of aromatic amines on the photopolymerization of 1,6-hexanediol diacrylate

The ability of aromatic amines to accelerate the photoinitiated polymerization of multifunctional acrylates in the presence of oxygen is shown to be dependent on the structure of the amine. For N, N-dimethylaniline, a rapid oxygen-scavenging process which proceeds by a radical-chain mechanism accounts for the large polymerization rate increase. Conversely, aniline cannot sustain an oxygen-scavenging process and inhibits the polymerization of air-saturated monomers. In general, the degree of rate enhancement and/or inhibition of the aromatic amines investigated is subject to the amine concentration.

Modulation of genotoxic and cytotoxic effects of aromatic amines in monolayers of rat hepatocytes.

Cultured rat hepatocytes exposed to 2-acetylaminofluorene (AAF), 2-aminofluorene (AF) or N-hydroxy-2-acetylaminofluorene (N-OH-AFF) for 3 hrs resulted in an increase in DNA repair measured as unscheduled DNA synthesis, with N-OH-AAF greater than AAF greater than AF. Cytotoxic effects were only seen with N-OH-AAF above 10(-6) M. alpha-Naphthoflavone increased the unscheduled DNA synthesis and cytotoxic effects of N-OH-AAF, whereas it decreased DNA repair and the covalent binding of AAF to cellular proteins. In contrast, very little effects of paraoxon were seen on the repair synthesis elicited by AAF, AF or N-OH-AAF. The addition of ascorbate reduced the covalent binding of AAF, the DNA repair synthesis caused by AAF and N-OH-AAF, and the cytotoxic effects of N-OH-AAF. The addition of pentachlorophenol or salicylamide all resulted in similar effects as ascorbate, through reduction of sulfation. Galactosamine, an inhibitor of glucuronidation, and the nucleophile GSH caused no or only minor effects of the activation of AAF, AF or N-OH-AAF as judged from the endpoints tested. These results are consistent with an arylnitrenium ion, a sulfate ester or a free radical as the arylamine metabolite causing cellular DNA damage, whereas the sulfate ester or a radical intermediate may be responsible for the cytotoxic effects of N-OH-AAF.

Effect of aromatic amines on the activity of cobalt bromide oxidation catalysts

Effect of aromatic amines on the activity of cobalt bromide oxidation catalysts

The Effect of Aromatic Amines on the Catalyzed Decarboxylation of 3-Oxo-glutaric Acid

Equilibrium constants have been measured for the formation of MA species, where M is divalent manganese, cobalt, nickel, or zinc, and A2− is the 3-oxo-glutarate ion. Equilibrium constants have also been measured for the reactions [Formula: see text], where B is 2,2′-bipyridyl or 1,10-phenanthroline. These constants were obtained by pH measurements at 25 °C and an ionic strength of 0.60. The results are compared with those for similar systems, especially as regards the tendency to form ternary mixed complexes of the type MAB.The rates of decarboxylation of the various MA and MAB species have been measured. The resulting rate constants follow the Irving–Williams order for stability constants, except that in both MAB species the cobalt compound decomposed slightly faster than the nickel compound. The aromatic base, which had been found earlier to have very little effect in copper complexes, increased the rate constants appreciably with other metals, especially with manganese and zinc. Usually 1,10-phenanthroline has a larger effect than 2,2′-bipyridyl. Some possible explanations of the results are considered.

Effect of aromatic amines on the diffusion of hydrogen into steel during cathodic polarization in acids

1. Direct measurements of changes in the mechanical properties of steel specimens after cathodic polarization and measurements of the quantity of hydrogen diffusing through a cathodically polarized steel membrane were used to study the effect of the molecular structure of certain aromatic amines on their ability to inhibit hydrogen charging of steel, cathodically polarized in acid solutions. 2. A relationship between the inhibiting power of aromatic amines and the electron density around the nitrogen atom was established. The higher the electron density, the higher is the inhibiting power of a given amine. 3. The ability of the compounds studied to inhibit hydrogen charging is associated with their ability to form chemisorbed films on a cathode surface, which prevent discharging hydroxonium ions from reaching the metal surface.

Inhibition of the Oxidation and Polymerization of Methyl Methacrylate. II. Effect of Aromatic Amines1

Inhibition of the Oxidation and Polymerization of Methyl Methacrylate. II. Effect of Aromatic Amines¹

The effect of 2-aminofluorene and related aromatic amines on the protein and ribonucleic acid metabolism of liver slices

The effects of some aromatic amines on the protein and ribonucleic acid metabolism in liver and kidney slices from rats and guinea pigs were investigated. 1. 1. The incorporation of 14C-valine into protein by rat liver slices was markedly inhibited by 2-aminofluorene (AF) and 2-acetylaminofluorene (AAF), which have a carcinogenic effect on rat liver. 2. 2. The non-carcinogenic aromatic amines aniline and 1-aminonaphthalene (1-AN) did not inhibit the incorporation of 14C-valine into protein by rat liver slices under similar conditions. 3. 3. The bladder carcinogen 2-aminonaphthalene (2-AN), which like most other aromatic amines is metabolized by liver, inhibited the incorporation of 14C-valine into protein by rat liver slices at least as much as did AF and AAF. 4. 4. In slices from guinea pig, an animal which is refractory to the carcinogenic effect of AF and AAF, these compounds inhibited the incorporation of 14C-valine into protein even more than in rat liver slices. 5. 5. Substitution of fluorine in position 7 of the AF molecule, which increases the carcinogenicity of this compound in liver, rather decreased the inhibitory effect in rat liver slices. A similar picture was observed with guinea pig slices, although the difference in this case was less pronounced. 6. 6. A certain time of preincubation was needed for the inhibitory effects to become manifest. The incorporation of 14C-valine into protein by rat kidney slices was not inhibited by the above compounds. These facts suggest that the true inhibitors were metabolitic derivatives of the administered substances. 7. 7. The incorporation of 14C-adenine into ribonucleic acid by rat liver slices was inhibited by AF, FAF and 2-AN under the same conditions as the valine incorporation, although to a somewhat lesser extent.