Abstract
Geometry optimized INDO calculations have been performed on 4-aminopyridine (2) and protonated 4-aminopyridine (1) in order to compare their optimized geometries, π-bond orders, C(4)–NH2 rotational barriers, charge densities, and π-electron distributions. It had previously been shown that 4-aminopyridine falls far off a linear correlation of ΔG° and ΔS° for the protonation equilibria of a series of 4-substituted pyridines. The calculations support the concept that a very high rotational barrier in (1) could cause this deviation. The contribution of a quinonoid resonance hybrid (1b) to (1) was greater than (2b) to (2). The π-cloud in (1) is polarized toward the ring nitrogen, relative to (2), and the C(4)–NH2 rotational barrier in (1)(27.3 kcal mol–1) is larger than in (2)(14.7 kcal mol–1).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the Chemical Society, Perkin Transactions 2
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
