Nitrogen proton affinities and amine basicity

TABLE 26. Force field (MMl) calculations of l,5-diazabicyclo[3.3.3]undecane 72 and 1,6-diazabicyclo[4.4.4]tetradecan 73 (distances in A, bond angles in degrees, relative energies in kcalmol1)111 

While all strain effects in monoamines are basicity weakening, it is possible to find cases in di- and polyamines where strain is relieved upon protonation, leading to increased basicity. This phenomenon is observed in 1,4-diaminobutane derivatives where an almost linear N... H—(N+) hydrogen bond in the mono-protonated derivatives leads to a stable, seven-membered ring structure. Thus, for example, the measured PA of l,6-diazabicyclo[4.4.4]tetradecane (73) is 228.3 kcalmol-1, about 11 kcalmol-1 higher than its monoamine analog 75, despite the similar, inwardly pyramidalized, nitrogen conformation of both neutral amines. 

TABLE 27. A comparison of selected torsional angles (degrees) of 3-phenyl-A-nitrosopyrrolidine, 81, as calculated by MM2 and measured by X-ray crystallography  

Cerioni has used MM2 calculations in a comparative analysis of 170 and 15N NMR spectra of a series of aliphatic and aromatic /V-nilrosamines119 (no computational details were given in this work). In particular, two groups of aliphatic (87-89 and 90-92) and 

and NMR spectra of N-nitrosamines Cerioni has used MM2 calculations in a comparative analysis of and NMR 

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