Infrared spectral studies on the orientation of the electron lone-pairs on nitrogen atoms

✍ Scribed by C.-Y. Chen; R.J.W. Le Fèvre

• Publisher: Elsevier Science
• Year: 1965
• Tongue: French
• Weight: 252 KB
• Volume: 6
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)84100-9

✦ Synopsis

In quinolizidine derivatives, infrared bands in the -1 2700-2800 cm region have been correlated with the presence of at least two g-hydrogen atoms oriented trans to the lone pair (1, 2, 3). c However a few exceptions e.g., 3-epialloyohimbone and 3-epialloyohimblne ( 4)] have already been reported. Recently, Haml~ et al (5) have attempted to rationalize such a "characteristic" absorption band in the infrared and also the "large" difference (0.93 p.p.m.) in proton magnetic resonant e (p.m.r.) chemical shifts of the a-hydrogen6 in axial and equatorial dispositions by proposing that in saturated cyclic nitrogen compounds in which the direction of the nitrogen lone pair is fixed; partial participation of the lone pair in a 6* C-pax orbital on the adjacent carbon takes place (see Fig. I), and that this generates some double bond character between Co and A with a simultaneous increase in electron density at the C, axial proton.