55100-40-8Relevant academic research and scientific papers
Nitrogen inversion barrier of 2-methyl-2-azabicyclo[2.2.1]heptane. The role of torsional strain in pyramidal inversion
Forsyth, David A.,Zhang, Weiyi,Hanley, John A.
, p. 1284 - 1289 (1996)
Low-temperature 13C NMR measurements indicate that the endo isomer of 2-methyl-2-azabicyclo-[2.2.1]heptane is about 0.3 kcal mol-1 more stable than the exo isomer. Rate constants for inversion from the endo to exo isomer were determined by NMR line shape analysis. The inversion barrier, ΔG?, of 7.2 kcal mol-1 is lower than that in model acyclic amines, despite an internal CNC bond angle that is less than the tetrahedral angle of 109.47°. Comparison with 7-methyl-7-azabicyclo-[2.2.1]heptane that has a small internal CNC angle and an unusually high barrier, as well as other cyclic and bicyclic amines, leads to the conclusion that torsional (eclipsing) strain plays a significant role along with angle strain in determining inversion barriers. Molecular mechanics calculations of the change in energy between pyramidal ground state and planar transition state account reasonably well for the observed barriers. New measurements of inversion barriers and their dependence on solvent are also reported for 2-methyl-2-azabicyclo[2.2.2]octane and l-methyl-4-piperidone.
NMR Studies of N-Methyl Derivatives of the 2-Azabicycloheptyl and -octyl Ring System; Kinetic Protonation in Determination of Invertomer Preferences
Belkacemi, Djaballah,Malpass, John R.
, p. 9105 - 9116 (2007/10/02)
The title compounds were studied by 1H, 13C, and 15N NMR spectroscopy.Since inversion at nitrogen is rapid on the NMR time scale even at low temperatures, kinetic protonation was used to estimate invertomer ratios at ambient temperature.Invertomer preferences appear to be consistent with the operation of steric factors.
