Aniline identification

Other Methods. A number of chemical methods can also be used for identification of aniline (69). Table 5 gives the specifications for a typical commercial-grade aniline. 

The first triaryknethane dyes were synthesized on a strictiy empirical basis in the late 1850s an example is fuchsine, which was prepared from the reaction of vinyl chloride with aniline. Thek stmctural relationship to triphenylmethane was estabHshed by Otto and Fmil Fischer (5) with the identification of pararosaniline [569-61-9] as 4,4, 4 -triaminotriphenyknethane and the stmctural elucidation of fuchsine. Several different stmctures have been assigned to the triaryknethane dyes (6—8), but none accounts precisely for the observed spectral characteristics. The triaryknethane dyes are therefore generally considered to be resonance hybrids. However, for convenience, usually only one hybrid is indicated, as shown for crystal violet [548-62-9] Cl Basic Violet 3 (1), for which = 589 nm. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

Figure 12.14 Chromatographic analysis of aniline (a) Precolumn chromatogram (the compound represented by the shaded peak is solvent flushed) (b) main column chromatogram without cryotrapping (c) main column chromatogram with ciyottapping. Conditions DCS, two columns and two ovens, with and without ciyottapping facilities columns OV-17 (25 m X 0.32 mm i.d., 1.0 p.m d.f.) and HP-1 (50 m X 0.32 mm, 1.05 p.m df). Peak identification is as follows 1, benzene 2, cyclohexane 3, cyclohexylamine 4, cyclohexanol 5, phenol 6, aniline 7, toluidine 8, nittobenzene 9, dicyclohexylamine. Reprinted with permission from Ref. (20).

Primary aromatic amines (e.g., aniline) and secondary aliphatic-aromatic amines (e. g., 7V-methylaniline) usually form triazenes in coupling reactions with benzenedi-azonium salts. If the nucleophilicity of the aryl residue is increased by addition of substituents or fused rings, as in 3-methylaniline and 1- and 2-naphthylamine, aminoazo formation takes place (C-coupling). However, the possibility has also been noted that in aminoazo formation the initial attack of the diazonium ion may still be at the amine N-atom, but the aN-complex might rearrange too rapidly to allow its identification (Beranek and Vecera, 1970). 

In the preceding section we concentrated on the rate-limiting steps of diazotizations in aqueous sulfuric and perchloric acid. The results were the identification of dinitrogen trioxide and (solvated) nitrosyl ions as electrophilic reagents, aniline and anilinium ion as nucleophilic reagents and an interpretation of the influence of acidity. 

Chlorotrifluoromethyl aniline (no. 73.) was found in the sediment samples. This compound is used as a reactant with chloro-aniline (no. 72) in the preparation of 4,4 -dichloro-3-(trifluoromethyl)-carbanilide, a disinfectant. Two other related compounds also found in some of the sediments were chlorophenyl isocyanate (no. 74) and chloro(-trifluoromethyl)phenyl isocyanate (no. 75). This suggests that some of the 4,4 -dichloro-3-(trifluoromethyl)-carbanilide may, in fact, exist in the sediment extracts but is decomposed in the injection port of the gas chromatograph, since it is very doubtful that the easily hydrolyzable isocyanates exist as such in the sediments. To strengthen this hypothesis some 3,4,4 -trichlorocarbanilide [none of the 4,4 -dichloro-3-(trifluorome-thyl)-carbanilide was available] was analyzed by GCMS. The injection port temperature was 300°C. As expected, none of the parent compound eluted from the column. However, mass spectra were obtained for chlorophenyl isocyanate, dichlorophenyl isocyanate, chloroaniline, and dichloroaniline. The presence of the carbanilides themselves (no. 76, 77, 78) was confirmed with the help of HPLC and mass spectral identification. 

To investigate the methylation of aniline by methanol on basic zeolite CsOH/ Cs,NaY, the CF MAS NMR technique was combined with SF protocols (242 ). In the first period, these protocols allowed the observation of adsorbate complexes formed on solid catalysts under steady-state conditions. In subsequent periods, an identification of adsorbates acting as intermediates of the further reaction was carried out. 

Phenylhydrazinc, as hydrochloride solution plus sodium acetate, reacts with polyhydroxy aldehydes or ketones yielding osazones or diphenyl-hydrazones, yellow solids, of definite melting point and utilized in identification of sugars, e.g.. phenyl-d-glucosazone. CH OH (CHOH), C (NNHC6H5)CH (NNHCftH,) plus aniline C6H5NH plus NH,... 

Shale oils. The identification of shale oils is not always easy. In density, refraction and insolubility in aniline they closely resemble mineral oils, but differ from these in being partially attacked by fuming nitric acid. 

TNT forms charge-transfer, or 7r, complexes with polycyclic aromatic hydrocarbons, aromatic amines, and aromatic nitro compds a number of these are listed below in Table 2. The complexes with three amines (diphenylamine, diethyl-aniline, p-anisidine) have characteristic colors this forms the basis for a rapid and convenient thin-layer chromatographic analytical procedure (Ref 34) for the identification of very small amounts of TNT. (For a discussion of the many color reactions of TNT, and of composite expls containing it, see Vol 3, C405-L ff)... 

Figure 12. Identification of N-methyl aniline in the synthetic mixture by EIEIO (a) Selection of N-methyl aniline (b) EIEIO fragments of N-methyl aniline in the mixture.

While the melting points of the aniline glycosides, the so-called anilides, are too variable for identification purposes, the partially etherified sugars form anilides which have reliable melting points and such anilides are widely used for identification purposes. Sirupy 2,3,5-trimethyl-D-ribose, for instance, has been converted into a crystalline anilide,89 presumably aniline 2,3,5-trimethyl-D-ribofuranoside. An investigation of the configuration and properties of such derivatives would seem highly desirable. 

Fluorobenzene or Phenyl Fluoride, F.C6H5 mw 96.10, colorless liq with benz odor, sp gr 1.0252 at 20°/4, fr p -41.9°, bp 84.9°, nD 1.4677 at 20° nearly insol in w miscible with ale eth. Can be prepd by di-azotizing aniline in anhyd HF followed by controlled thermal decompn of the diazonium fluoride (Ref 3). Used as identification reagent for plastic or resin polymers and as insecticide intermediate Refs 1) Beil 5, 198, (108), [147] [520]... 

Two structures that easily accept protons, and thus make certain molecules bases, are NH and NH. For easy identification, many bases are written with these structures tacked onto the end of the molecular formula. For example, we write the bases dimethylamine, methylamine, and aniline as (CH3)2NH, CH3NH2, and... 

Identification of Trichloromethyl Chloroformate. This substance may. be identified by its reaction with an aqueous solution of aniline (3 100). Like phosgene and dichloromethyl chloroformate, a white crystalline precipitate of diphenyl urea forms, which may be confirmed by microscopic examination (rhombic prisms) or by a determination of its melting point (236° C.). 

Polyaniline filaments have been synthesized in mordenite and zeolite Y. 3 Aniline was sorbed from hexane solution into the dehydrated zeolites containing different levels of hydroxyl groups (an alternate route is the exchange of anilinium salt into the host, see ref. 93b). Oxidative polymerization was achieved by immersion of the loaded zeolites into an aqueous solution of peroxydisulfate, as demonstrated by spectroscopic identification and recovery of the encapsulated polymer (Figure 10). 

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