Aromatic Amines Anilines

3 Aromatic Amines (Anilines). The molecular ion peak (odd number) of an aromatic monoamine is intense. Loss of one of the amino H atoms of aniline gives a moderately intense M - 1 peak loss of a neutral molecule of HCN followed by loss of a hydrogen atom gives prominent peaks at mlz 66 and 65, respectively. 

---

One of the most important derivatives of benzene is nitrobenzene. The nitro group is —NOi. Nitrobenzene is important chiefly because it is readily converted into an aromatic amine, aniline, by reduction. One preparative procedure uses zinc as the reducing agent ... 

Primary aromatic amines (aniline, 3-toluidine, 4-anisidine and 3-chloroanilinc) react with 4 to give 2-[2-(arylamino)-l-cyanoviny]]benzimidazoles9 (see Houben-Weyl, Vol.E8c, p 314 with an experimental procedure).289... 

When aromatic compounds are reacted with hydrogen, the catalyst used determines which part of the molecule reacts. Thus, with the right catalyst, a nitro group can be converted to an amine without adding hydrogen to the ring. In this case the simplest aromatic amine (aniline) is produced. 

The first example of acid catalysis appeared in a 1934 patent in which it is claimed that surface catalysts, particularly hydrosilicates of large surface area , known at that time under the trade name Tonsil, Franconit, Granisol, etc. lead to a smooth addition of the olefine to the molecule of the primary aromatic amine . Aniline and cyclohexene were reacted over Tonsil at 230-240°C to give, inter alia, the hydroamination product, N-cyclohexylaniline [47]. 

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. 

Aromatic amines are of considerable importance commercially. The simplest aromatic amine, aniline. ChH5NH2, is used in the production of various dyes and chemicals for color photography. 

As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant. Pinene explodes sharply acetone and ethanol ignite, then explode ether evolves gas, then explodes after a few s delay. Small amounts of primary aromatic amines-aniline, toluidines, xylidines, mesidine-ignite on contact, while larger amounts exploded dangerously, probably owing to rapid formation of diazonium perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar reason). 

Phenols (p-cresol, guaiacol, pyrogallol, catechol) and aromatic amines (aniline, p-tolidine, o-phenyldiamine, o-dianisidine) are typical substrates for peroxidases [90 -109]. These compounds are oxidized by hydrogen peroxide or hydroperoxides under peroxidase catalysis to generate radicals, which after diffusion from the active center of the enzyme react with further aromatic substrates to form dimeric, oligomeric or polymeric products. 

Aromatic amines (anilines) may become activated in vivo to form reactive amines. These are nucleophiles and may attack DNA, forming covalent modifications. Aromatic nitro compounds can be metabolised to also form reactive amines. A-nitroso compounds result in the alkylation of oxygen sites in DNA bases (0-6 in guanine and 0-4 in thymidine) [8,10]. 

Aromatic Amines (Anilines) The molecular ion peak (odd number) of an aromatic monoamine is intense. Loss of one of the amino H atoms of aniline... 

The procedure has also been applied for the hydroxylation of aromatic amines. Aniline and its /V-alkyl-substimted derivatives show similar behavior under similar conditions to afford the meta-substi tuted aminophenols as the major hydroxylated product.627 Product formation was interpreted by the attack of protonated hydrogen peroxide on the anilinium ion protected by /V-protonation from oxidation or degradation. Indoles, indolines, and tetrahydroquinoline have also been successfully hydroxylated with H202 in HF-SbF5 with the hydroxyl group meta to the nitrogen function.559,628 Hydroxylation of tryptophane and tryptamine derivatives affords pretonine and serotonine derivatives in 42% and 38% yields, respectively.629... 

The largest group of organic molecular compounds, in which hydrogen bond formation plays no part, are the compounds, usually in the ratio 1 1, between on the one hand aliphatic and aromatic nitro compounds (nitromethane, tetranitro-methane, chloropicrin CC13N02, nitrobenzene, s-trinitrobenzene, picric acid), quinones, anhydrides (phthalic acid-and maleic acid anhydride) and ketones with on the other hand especially aliphatic and aromatic amines (aniline, pyridine), unsaturated aliphatic and aromatic hydrocarbons, ethers etc. 

The authors first considered the attachment of the aldehyde component to the SP using the AMEBA (acid-sensitive methoxy benzaldehyde) PS resin (100). 4-Carboxy-benzaldehyde and two different amines were reacted to produce the resin-bound intermediates 6.1 and 6.2 on a 100-g scale according to the reaction scheme shown in Pig. 6.9, with good yields resulting from an optimization of the reaction conditions. Resin-bound 6.1 was reacted with the standard olefin (cyclopentadiene, 6.3) and an aromatic amine (aniline, 6.9) and, after optimization of the reaction conditions, the desired tetrahydroquinoline 6.14 was obtained in good yield and purity after cleavage. 

Fierz-David and Ziegler (301) first applied this method to azo compounds. Ethyl acetoacetate and various aromatic amines (aniline, o- and p-toluidines, m-xylidine, o-anisidine, and chloroanilines) were convereted to acetoacetanilides and then coupled with diazotized sulfanilic acid. The azo dyes (38) were reduced with stannous chloride in hydrochloric acid to the corresponding aminoaceto-acetanilides (39), which in alkali formed the dihydropyrazines (40). Catalytic reduction of o-hydroxyphenylglyoxal phenylhydrazone in acetic acid over palladium has been shown also to give 2,5-bis(o-hydroxyphenyl)pyrazine (302). Reduction of chemical means has been shown to give... 

Aromatic amines—those in which nitrogen is attached directly to an aromatic ring—are generally named as derivatives of the simplest aromatic amine, aniline. An aminotoluene is given the special name of toluidine. For example ... 

During the five decades commencing 1840, chemists established a comprehensive chemistry of aromatic amines. Aniline was characterized by its feeble basicity and sensitivity to oxidants, the latter explaining why the colorless, odorless pure liquid darkens on exposure to air and light. It also takes on a characteristic odor. Methods of laboratory preparation... 

UVV spectrophotometry is one of the simplest and fastest methods for determination of aromatic amines and may serve also for identification purpose with the aid of diode array detectors. A study was carried out on the performance of direct phase (silica gel) and RP (Cis) columns, using a MeOH-O.l M NaC104 mobile phase, for the HPLC-UVD (at 256 nm) analysis of five aromatic amines aniline (la), 1- (8a) and 2-napththylamine (9a), di- (DPA) and triphenylamine (TPA). Good resolutions and separation factors were observed with the RP column for la vs. the other analytes and for 8a or 9a vs. DPA or TPA however, separation of the 8a-9a or DPA-TPA pairs was poor210. 

The presence of strong interactions between the amino lone-pair electrons and the aryl it electrons in the electronically excited states of aromatic amines (anilines) differentiates their spectroscopy and photochemistry from those of saturated amines and aromatic... 

As in pyrroles, the A-hydrogen in indoles is much more acidic (pK 16.2) than that of an aromatic amine (aniline has pK 30.7). Any very strong base will effect complete conversion of an A-unsubstituted indole into the corresponding indolyl anion, amongst the most convenient being sodium hydride, n-butyUithium or an alkyl Grignard reagent. 

Aromatic amines (aniline and substituted anilines) are used as intermediates in industrial and pharmaceutical chemistry [11], Because of their aromatic character, they strongly absorb in the UV range. A recent study has shown the great interest for the study of aromatic amines from azo-dyes reduction using UV spectrophotometry [12], On the opposite, aliphatic amines do not absorb directly (see Section 4.2). 

---