2- Naphthylamine intramolecular hydrogen bonds

What about jr-electron donor substituents on nitrosoarenes other than dimethylamino Pedley gives us the enthalpies of formation for three hydroxy derivatives the isomeric 4-nitroso-l-naphthol, 2-nitroso-l-naphthol and l-nitroso-2-naphthol, species 45-47 respectively. Of the three species, only the first cannot have an intramolecular hydrogen bond. By analogy to nitrophenols75 — there being no thermochemical data for the more related and hence relevant nitronaphthols—we expect that species 46 would be less stable than 45. After all, gaseous 2-nitrophenol is ca 20 kJ mol 1 less stable than its 4-isomer. We recall from the discussion of the isomeric naphthylamines that 1- and 2-naphthol are of almost identical stability. This suggests that species 46 and 47 should be of comparable stability. Both expectations are sorely violated by the literature results the enthalpies of formation of species 45, 46 and 47 increase in the order —20.3 4.9, —5.4 6.2 and 36.1 4.7 kJmol-1 respectively. If there is experimental error, where does the error lie ... 

Intramolecular hydrogen bonds in anilines62 and in naphthylamines affect the HNH angles and the a-character of the nitrogen bonding orbitals with the consequence of affecting the p.K a value of the NH2 group99. 

The crystal structure of l-(3 -methylphenylazo)-2-naphthylamine was determined by the X-ray diffraction method. No dynamic disorder was observed in the crystalline state, and the azo group was found to adopt trans-conformation with six-membered ring formed by the intramolecular hydrogen bond. In the solid state, CP MAS NMR spectrum of its acetamide derivative the doublet signals were found. The DFT computations were employed for the conformational analysis of 2-naphthylamines. 

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