Aryl-amino radical

An illustration of the abiotic reactions that are believed to dominate the fate of aromatic amines in soils and sediments is given in Figure 12. In oxic environments, numerous reactants and reaction schemes have been suggested to account for the rapid disappearance of anilines and related compounds. Many of the products obtained from the oxidation of aromatic amines can be rationalized by examination of the reactivity of the aryl-amino radical, ArNHV Delocalization by resonance stabilizes the aryl-amino radical but makes the ortho- and para- positions of the ring subject to reactions (41, 46). 

Sulfonyl radicals are often represented simply as XS02 where the sulfur atom is understood to be bonded to two oxygens as well as to X the moiety X may be an alkyl, aryl, amino or alkoxy group. The unpaired electron does not reside on one particular atom but rather it extends over all atoms of the S02 group. It should be noted that in recent literature some authors refer to alkanethiyl peroxyl radicals, the adduct of alkanethiyl (RS ) to molecular oxygen, as RS02 rather than RSOO and the fact has already caused some inconvenience. 

A study of the effect of the structure and size of the amine radical (butylamine, dibutylamine, hexylamine, piperidine, aniline) on its reactivity in the nucleophilic replacement of tosyloxy groups in cellulose tosylate has shown (29) that this reactivity depends primarily on the basicity of the amine. TTiis assumption was confirmed by a study of the interaction of cellulose toxylates of different degrees of substitution (DS from 0.3-1.7) wit iminodiacetic and anthranilic acids 30, 31). TTie degree of substitution of the reaction products with respect to the N-carboxyalkyl(aryl)amino groups was found to be lower than that of the corresponding N-alkyl(aryl)araino derivatives. 

In weakly alkaline solution, hydrogenation with a platinum catalyst (20°, atmospheric pressure) is limited to the sugar radical, and 1-arylamino-l-deoxy-2-ketoses are then readily converted to the two epimeric 1-aryl-amino-l-deoxy-glycitols. However, both epimeric aminoglycitols have actually been isolated in only one experiment. According to the experimental conditions, one of the two possible isomers is usually formed to the almost complete exclusion of the other reaction product. As Weygand explained, such behavior is to be expected, since the enol form of the aminoketose can... 

Although the hot aniline molecules undergo the aryl-amino C—N bond cleavage (Scheme 2), this reaction is inefficient for anilines in the excited states. In contrast, the anilino-alkyl C—N bond homolysis has been observed for several aniline derivatives. For example, methyl radical (Me") and anilino radical (PhN Me) have been detected as the products of the photoirradiation of tetramethylphenylenediamine (25) and N,N-dimethylaniline (lb), respectively, in 3-methylpentane at 77 K124,125. 

From the effect of solvent (Table 15) it is evident that the reactions discussed are nitrene reactions hydrogen-rich solvents suppress ring contraction and give rise to solvent dimer (bibenzyl) and/or a yellow nitrene dimer. The structure of the dimer is not known, but one possibility is shown in 144. A similar (colorless) dimer was obtained from 9-phenanthridylnitrene at 500 ° 7). Xhe two dimers formed from 137 and 141 in cyclohexane have nearly identical IR spectra. How could a hydrogen-rich solvent promote dimeriztion There is evidence from aryl azide decomposition in solution that amino radicals are formed first, and these dimerize and dehydrogenate as shown for 1-naphthylnitrene in [Eq. (48)] 82). 

Thermolysis studies of arylamines have shown that homolytic fission of the N—At bond occurs, giving aryl and amino radicals, the former undergoing dimerisation to the corresponding biaryl while the amino radical abstracts H, forming ammonia. 

The terminal amino group of 2-hydrazino-4-phenylthiazole is also the reactive center in reactions with activated aryl halides such as 288. A solution of the product (289) obtained from this reaction when shaken with PbOj gives a deeply colored radical, whose structure has been studied by ESR (Scheme 173) (532. 533). 

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