Aromatic amine bands

Table 7.2 The list of Aromatic amines banded in Europe according to the EU Directive 2002/61/EC...

Characteristic strong C—N stretching bands in the spectra of aromatic amines have been assigned as in Table 3.4. 

The basicity of the aromatic amine iV-oxide can be substantially varied by the introduction of substituents on the aromatic ring. IR spectra of free N-oxides display a prominent band between 1200 and 1300 cm-1, attributable to the nitrogen-oxygen stretching frequency v(NO). The more activating the substituent, the lower the energy of the absorption. Upon coordination, v(NO) is decreased by up to 60 cm-1. IR data for pyrazole and pyridine derivatives are given in Table 42.281-286... 

Figure 6.31 Molecular structure of a typical electroactive aromatic amine, with a redox potential well into the band-gap region...

Here, we shall consider several macroscopic features of the plastic deformation of glassy epoxy-aromatic amine networks. Mostly, the tensile or compression deformation has an inhomogeneous character. Usually, diffuse shear zones (or coarse shear bands) are clearly seen at room temperature deformation. Shear zones start from the defects on the sample boundaries or voids (dust) in the bulk. At higher temperatures, the samples are homogeneously deformed with neck formation (DGER-DADPhS, P = 1) 34>. 

The latter mechanism is met in amine-vinyl monomer systems [41-46] (see Scheme 4). Due to the small n-acceptor ability of normal substituted vinyl monomers, an interaction in the ground-state level does not take place. The exciplexes assumed are detectable in aromatic amine-acrylonitrile (AN) systems by their emission spectra, as is shown in Fig. 1 for typical examples. The emission bands at 350 nm (by JV,JV-dimethyl-p-toluidine (DMT)) and 370 nm (by p-phenylene diamine (TMPD) result from the normal fluorescence of the isolated amine. As can be seen, the intensity of the exciplex emission is much higher in the DMT-AN system. This corresponds to the higher polymerization efficiency of that system (<)>[, by A. = 313 nm and 80 K 0.6 for DMT 0.15 for TMPD [46]). Mainly, the much higher dipole moment of DMT (1.1 D) is responsible for this result. The cation radicals [46] or neutral radicals [42] of the amines formed after PET and proton transfer have been detected by ESR measurements. As expected, the rate of photopolymerization of the systems discussed increases with increasing... 

Other aromatic amines with TICT-active amino groups include naphthyl-amines like DMANCN, which shows a well-separated dual fluorescence, and DANCA or related dyes which are used as fluorescence probes (sensing micropolarity) in biological investigations. In the latter case, only one (red-shifted) band (or two strongly overlapping bands) can be seen. 

The position, extinction coefficients and band half-widths of anilines and of polycyclic aromatic amines were studied by infrared spectroscopic measurements a long time ago34. One purpose was to understand the hybridization of the nitrogen atom bonded to unsaturated systems35,36. Infrared spectroscopic parameters of the NH2 group in substituted anilines were correlated with the Hammett sigma substituent constants37. 

NIR spectrophotometry in the region from 8000 to 4000 cm-1 was used to measure the kinetics of copolymerization of an aromatic bismaleimide (72) derived from an aromatic diamine (e.g. 5a), taking place at 160 to 180 °C. The following NIR spectral ranges were useful for this study primary amine first overtones (vn h) at 7000 to 6400 cm-1, double bond first overtone (vc=c-h) at 6100 cm-1, aromatic first overtones (vc-h) at 6000 to 5750 cm-1, aliphatic first overtones (vc-h) at 5750 to 5350 cm-1 and primary aromatic amine combination bands first overtones (vn h + <5nh2) at 5150 to 4800 cm-1. The process consisted mainly of a second-order Michael addition, as depicted in equation 14, and not the plausible imide opening to yield a maleic dianilide (119), as shown in equation 15. A Michael addition between maleimide moieties and secondary amine moieties present in the products (118) also takes place, however at a rate of about one fourth of that of the primary amine moieties. To improve the SNR of the measurements, usually the results of... 

Groups of aromatic amines may be distinguished by their difference absorption spectra, where spectra performed in neutral solution (pH 8) are compared to those taken in acidic solutions (pH 1.5). Thus, the difference spectra of the anilines show a slight hypsochromic shift of the bands from 290 to 280 nm and from 235 to 230 nm. On the other hand, the difference spectra of heterocyclic aromatic amines, such as pyridines, quinolines and isoquinolines, are characterized by the presence of strong negative bands, attributed to a hyperchromic effect caused by protonation268. 

M. J. Zeilmaker, H. J. van Kranen, M. P. Van Veen and J. Janus, Cancer Risk Assessment of Azo Dyes and Aromatic Amines from Tattoo Bands, Folders of Paper, Toys, Bed Clothes, Watch Straps and Ink, RIVM Rapport 601503019, 2000. http //www.rivm.nl/bibliotheek/rapporten/ 601503019.html... 

Such aromatic amines and diamines, as diphenylamine, iV-methyl-diphenylamine, triphenylamine, benzidine, p-phenylenediamine, etc., are known to have low ionization potentials (75) and to yield univalent positive molecular ions (semiquinones) under ultraviolet irradiation in rigid media (76), or by oxidation in solutions (77). These molecular ions possess characteristic absorption bands in the visible range. 

Figures 3.16(a) and (b) show the MIR spectra in two spectral regions for the TGDDM resin (Ciba MY721) and the aromatic amine hardener DDS as well as the mixture containing 27% DDS, which is typical of commercial formulations used in composite materials. The assignments of the significant bands in the spectra are given in Tables 3.2 for the TGDDM (MY721 resin) and 3.3 for DDS.

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