N-H bonds in anilines

The broken bonds (boldface=dissociated atom) AfH°(R), kcal/mol (kJ/mol) BDEs (boldface = recommended data reference in parentheses) Methods (reference in parentheses)  

4-Methoxy-N-phenyl- benzenamine 4-CH30CsH4NHPh 85.1 355.9 Correlation 2000DEN/DEN 

N-(4-phenoxy)phenyl- 2-naphthalenamine 2-CioH7NHC6H4(4 -C6HsO) 83.5 349.5 Correlation 2000DEN/DEN 

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The initial step of the cycle forming 23 was supported by separate stoichiometric reachons involving similar Ir(I) complexes that oxidatively added the N—H bond of aniline (see Section 6.5.2). It should be noted that norbornene does not form stable adducts with electron-rich Ir(I) complexes such as those used in this catalysis (R. Dorta and A. Togni, unpublished results). 

The pATa of the aminium ions is generally lower than those of the corresponding amine. The greater acidity of the aminium ion can be attributed to the greater amoimt of s character in the lone-pair orbital of the amine radical, (CH3)2N , which is sp -hybridized compared, with the more basic lone pair orbital in (CH3)2NH, which is sp -hybridized. In contrast, the pA a of the anilinium radical is much higher than that of the protonated aniline. The basicity of the anilinium radical is comparable with that of (CH3)2NH+ , reflecting the sp -hybrid character of the N-H bonds in the two species. The low basicity of the parent aniline results from... 

In infrared depletion spectroscopy of the neutral aniline/pyrrole205 complex, both spectroscopic observation and theoretical calculations indicate the presence of a hydrogen bond between one of the N—H bonds of aniline and the n system of pyrrole, as illustrated in 129. 

Photodissociation of the N—H bond of anilines could occur, albeit with low quantum yield in most cases, and form hydrogen atoms and aminyl radicals (equation 3)113. 

The absolute value of 7(15N-H) in some enamines (148) was found to be about 91 Hz, (Table XXXII, note g), larger than in aniline (about 83 Hz), and comparable to those for urea, some amides and their vinylogues. This has been explained in terms of an increase in the s-character of the N-H bond in such structures in comparison with aniline. 

BDEs ofN-X bonds 7.1 N-H bonds 7.1.1 N-H bonds in non-anilines Table 7.1.1 N-H BDEs in Non-Anilines ... 

Photolysis of 2-, 3- and 4-fluorophenylazide (39a,b,c) in aniline gives the products (40), (41) and (42) in the yields shown in Scheme 8. " With 2,6-difluoro- and 2,3,4,5,6-pentafluorophenyl azide, however, ring expansion to azepine products analogous to (42) is suppressed, and the corresponding unsymmetrical azobenzenes cf. 41) are formed in 50% and 55% yield, respectively. The azobenzenes are presumed to arise from insertion of a singlet nitrene into an N-H bond of aniline, followed by oxidation of the resulting hydrazine. 

The NH/tt interactions in other complexes were also reported. The MP2 calculations of aniUne complexes with ethylene, propene and 1-butene suggest an NH/tt interaction between the N - H bond of aniline and the double bond of the alkene for the propene and 1-butene complexes, with a CH/a-type interaction between the CH bond and the lone pair of nitrogen of anihne for the ethylene complex [103]. The MP2/6-311G -level optimized geometry of the pyrrole dimer shows that the dimer prefers the tilted T-shaped orientation, in which one monomer points toward the ring plane of the... 

The experimental evidences for this reaction are the same as in the case of phenols (see earlier). The BDE of N—H bonds of aromatic amines are collected in Table 15.5. They vary for the known amines from 387 kJ moh1 (aniline) to 331 kJ mol-1 (phenothiazine). 

The AES results indicate that the aniline coverage is more than two times greater than the maximum coverage based on van der Waals radii. The TPR results show this species is too stable to be a condensed multilayer. Hence, we conclude that aniline polymerized forming a very stable polymer layer. In addition, the absence of infrared bands corresponding to C=C stretches or ring vibrations indicated that the poly(aniline) film was formed with the phenyl rings parallel to surface. The infrared results also indicated that the poly(aniline) film had N-H bonds which were oriented perpendicular relative to the surface. 

A combined application of direct calorimetric measurements and thermochemical investigations has made possible to obtain a number of important thermochemical quantities characterizing the interaction of the N—H bond of the amine with the epoxy ring 53). Combustion and evaporation enthalpies of phenylglycidyl ether and its condensation products with aniline and butylamine have been determined. Standard enthalpies of the formation of these compounds, strain energies of the epoxy ring in the phenylglycidyl ether molecule and — AH values for the three-phase states, which are most important for the determination of the true thermodynamic reaction characteristics, have been estimated. 

The effect of adsorbing aniline is shown in Fig. 19. The surface OH band at 1.365 u disappears, and the N—H band of aniline at 1.52 u shows a slight shift from the position of this band in dilute solutions of CC14 (1.50 u). Yaroslavskii and Terenin attributed the disappearance of the OH band to the formation of hydrogen bonds, 0—H N. The disappearance of the surface OH bands has also been observed in other experiments. 

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