Nitroanilines analysis

An azo coupling reaction of monatomic phenols with diazotized 4-nitroaniline has been investigated. By HPLC, NMR, elemental analysis, UV and IR spectroscopy it has been shown that the azo derivatives of o-guaiacol, o- and m-cresols interact with an excess of diazonium in pH interval of 4,5-9,5 and form corresponding 4,4-di(4-nitrophenylazo)-2,5-cyclohexadien-1 -ones. 

The procedure of simultaneous extracting-spectrophotometric determination of nitrophenols in wastewater is proposed on the example of the analysis of mixtures of mono-, di-, and trinitrophenols. The procedure consists of extraction concentrating in an acid medium, and sequential back-extractions under various pH. Such procedures give possibility for isolation o-, m-, p-nitrophenols, a-, P-, y-dinitrophenols and trinitrophenol in separate groups. Simultaneous determination is carried out by summary light-absorption of nitrophenol-ions. The error of determination concentrations on maximum contaminant level in natural waters doesn t exceed 10%. The peculiarities of application of the sequential extractions under fixed pH were studied on the example of mixture of simplest phenols (phenol, o-, m-, />-cresols). The procedure of their determination is based on the extraction to carbon tetrachloride, subsequent back-extraction and spectrophotometric measurement of interaction products with diazo-p-nitroaniline. 

Li Y.S., Vo-Dinh T., Stokes D.L., Yu W., Surface-enhanced Raman analysis of p-nitroaniline on vacuum evaporation and chemically deposited silver-coated alumina substrates,Appl. Spectrosc 1992 46 1354-1357. 

The fundamentally important case p-nitroaniline (PNA), the high symmetry parent molecular unit of MNA, presents an excellent example for both experimental methodology and theoretical analysis. In the C 2 v symmetry for PNA and second harmonic generation, the measured principal component 3X is given by... 

More recently, a colorimetric-based LAL procedure has been devised. This entails addition to the LAL reagent of a short peptide, susceptible to hydrolysis by the LAL clotting enzyme. This synthetic peptide contains a chromogenic tag (usually para-nitroaniline, pNA) which is released free into solution by the clotting enzyme. This allows spectrophotometric analysis of the test sample, facilitating more accurate end-point determination. 

Crystal data (by X-ray diffraction analysis) and calculation of net 7r-electron population for 7V,7V-dialkyl-p-nitroaniline and for 3,5- and 2,6-dimethyl-4-nitroaniline indicate that... 

Fig. 3.61. HPLC-UV chromatogram at 230 nm for the analysis of the aromatic amines listed. (1) 1,4-Diaminobenzene (2) 2-chloro-l,4-diaminobenzene (3) 2,4-diaminotoluene (4) benzidine (5) 4,4 -oxidianiline (6) aniline and 4-nitroaniline (7) o-toluidine (8) 4,4 -methylenedianiline (9) 3,3 -dimethoxibenzidine (10) 3,3 -dimethylbenzidine (11) 4-chloroaniline and 2-amino-4-nitrotoluene (12) 4,4 -thiodianiline (13) p-cresidine (14) 2,4-dimethylaniline (15) 2-naphty-lamine (16) 4-chloro-o-toluidine (17) 4,4 -methylene-di-o-toluidine (18) 2,4,5-trimethylaniline (19) 4-aminobiphenyl (20) 3,3 -dichlorobenzidine (21) 4,4 -methylenbis (2-chloroaniline) and (22) o-aminoazotoluene. Reprinted with permission from M. C. Garrigos et al. [130].

The second aspect of our nitroaniline investigation concerns the analysis of (a) and Pvec in terms of the excited states contributions. The N-dependence of (a(0 0) is very similar for the three compounds and saturates for N = 20 (Fig. 9). Moreover, at most 10 excited states contribute significantly. For Pvec(0 0, 0), the On graphs (Figs. 10-12) exhibit some differences among the isomers. For -NA, 3 states present a dominant Oni state 3 (On = 0.96), state 6 (On = 0.62) and state 13 (On = -0.47). For the two other... 

This system resolved the aniline peak (retention time (rt) = 2.67 min) from the benzidine peak (rt = 2.27 min) as can be seen in Figure 2. Other potential interferences were selected for study by looking at the expected fragments from the reduction of various dyes. Reduced dye samples were spiked with aniline (rt = 2.67 min), -aminophenol (rt = 1.97 min), -phenylenediamine (rt = 1.93 min) and -nitroaniline (rt = 3 16 min). None of these materials interfered with the detection of the benzidine peak. To determine if other types of dyes might interfere with the analysis, two sets of filters were spiked at low and high levels separately with C.I. Direct Red 28 (13 7 yg and 137 yg), C.I. Direct Blue 53 formulation (o-tolidine-based) (21.2 yg and 212 yg) and C.I. Direct Blue 8 formulation (o-dianisidine-based)(23.3 yg and 233 yg). 

Aniline, Polynltro Derivatives. As no info is available on the analysis of these compds, we asked the opinion of Mr, F. Pristera and Dr H. Walter, who had wide experience in analysis of polynitro derivs of toluene, phenol, etc. If the sample is a solid, its mp must be detd and if it is a liquid, its bp. Next comes the analysis by lR(if an apparatus is available). Experiments at PicArsn showed that IR spectrograms of various nitrated derivs of toluene permitted distinguishing, not only the degree of nitration but also the position of NOa groups (Refs 13 14). In later work spectrograms of o- and p-nitroanilines [See paper by F. Prist era et al published in Anal Chem 32, 497(1960)] showed distinct differences between these two compds. 

In this method, an ale soln of benzene-sulfonic acid(previously standardized with phosgene by weighing the pptd diphenyl-carbamide) is added from a burette to a sample of anilinefor its nitrated compd not higher than tetranitro-) until the appearance of a dirty-bluish coloration, when a drop of the reaction mixt is placed on a filter paper previously impregnated with amino-/S-naphthol indicatorfspot test). This method is not applicable for analysis of penta-nitroaniline(Ref 15)... 

We started the analysis of the sulfonyl group as an acceptor with the calculation of 4-methylsulfonylaniline (I), which is an analogue of p-nitroaniline (II), and their methylated derivatives (III, and IV, respectively). We have found that while the ground state dipole moments are comparable for the nitro and sulfone derivatives (Table I), the p coefficients are different in magnitude, and depend on the method of calculation (Table I). 

It has been known experimentally(4) that much of the second order susceptibility generally arises from the lowest singlet excited state. For any particular molecule, the recently introduced Missing States Analysis (MSA)(5,6). can show, via calculation, to what extent P is dominated by the first excited state. For instance, the P of p-nitroaniline has been shown by MSA to be heavily dominated by the first excited state, at least with a PPP (Pariser-Pople-Parr) Hamiltonian and standard basis. The result of these findings is that one can often approximate Equation (4) by including only one excited state in the sum, there-by arriving at a two-level model ... 

Selected data published by Patsias and Papadopoulou-Mourkidou [114] illustrate sorption s dependence on sample volume (Figure 2.36). Their research pursues development of an automated online SPE-HPLC methodology for analysis of substituted anilines and phenols. Recovery (%) was measured for numerous compounds on various polymeric sorbents, but the only data presented here are those in which a styrene-divinylbenzene polymeric sorbent was used for analysis of aniline, phenol, 4-nitroaniline, and 4-nitrophenol. Aqueous sample volumes of 5, 10, 25, 50, 75, 100, 125, and 150 mL were acidified to pH 3 before SPE. 

Different methods for the study of selective solvation have been developed [118, 120] conductance and Hittorf transference measurements [119], NMR measurements (especially the effect of solvent composition on the chemical shift of a nucleus in the solute) [106-109], and optical spectra measurements like IR absorption shifts [111] or UV/Vis absorption shifts of solvatochromic dyes in binary solvent mixtures [124, 249, 371]. Recently, the preferential solvation of ionic (tetralkylammonium salts) and neutral solutes (phenol, nitroanilines) has been studied particularly successfully by H NMR spectroscopy through the analysis of the relative intensities of intermolecular H NOESY cross-peaks [372]. 

In 1994, a review on the further development and improvement of the n scale was given by Laurence, Abboud et al. [227], They redetermined n values for a total of 229 solvents, this time using only two (instead of seven) solvatochromic nitroaromatics as indicator compounds, i.e. 4-nitroanisole and A,A-dimethylamino-4-nitroaniline, for good reasons see later and reference [227] for a more detailed discussion. A thermodynamic analysis of the n scale [and the t(30) scale] has been reported by Matyushov et al. [228]. Using six novel diaza merocyanine dyes of the type R-N=N-R (R = N-methylpyridinium-4-yl or A-methylbenzothiazolium-2-yl, and R = 2,6-disubstituted 4-phenolates or 2-naphtholate) instead of nitroaromatics as positively solvatochromic probe compounds, an analogous n azo scale was developed by Buncel et al., which correlates reasonable well with the n scale, but has some advantages for a detailed discussion, see references [333], Another n scale, based solely on naphthalene, anthracene, and y9-carotene, was constructed by Abe [338], n values are mixed solvent parameters, measuring the solvent dipolarity and polarizability. The differences in the various n scales are caused by the different mixture of dipolarity and polarizability measured by the respective indicator. The n scale of Abe is practically independent of the solvent dipolarity, whereas Kamlet-Taft s n and Buncel s n azo reflect different contributions of both solvent dipolarity and polarizability. 

Method A was used. 2.0 g of p-CD (1.8 mmol) was dissolved in 100 ml of distilled water, and the solution was filtered. p-Nitroaniline (PNA), 0.25 g (1.8 mmol), was dissolved in 40 ml of diethyl ether, and added all at once to the aqueous CD solution. The mixture was stirred, open to the atmosphere to allow evaporation of the ether, overnight, and then filtered. The yellow precipitate was washed with ether and dried. Yield, 1.4 g, for which CH and N analysis indicated the inclusion of 4-6 moles of water per mole of complex. The actual degree of hydration varied from preparation to preparation. Melting occured with decomposition near 288-289 °C. 

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