Nature of transmission of polar substituent effects in γ-disposed bicyclo[2.2.1]heptane (norbornane) and adamantane ring systems as monitored by 19F NMR: A DFT- GIAO and – NBO analysis

William Adcock,Andrew Schamschurin,Julian F Taylor,Antigoni Kotali

doi:10.3998/ark.5550190.0010.504

Abstract

Nature of transmission of polar substituent effects in γ-disposed bicyclo[2.2.1]heptane (norbornane) and adamantane ring systems as monitored by 19F NMR: A DFT- GIAO and – NBO analysis

Highlights

Over the years we have reported systematic studies of polar substituent effects in several remotely substituted polycyclic alkanes utilizing 19F chemical shifts as sensitive electronic probes.[1]
Approximations are unavoidable in order to analyse 19F substituent chemical shifts (SCS) in terms that have proved useful in the case of chemical reactivity
Recently,[6] we presented computational studies (DFT-GIAO calculations) coupled with natural bond orbital (NBO) analyses of 4-substituted (X)bicyclo[2.2.2]oct-1-yl fluorides(1) and 3

Summary

Introduction

Over the years we have reported systematic studies of polar substituent effects in several remotely substituted polycyclic alkanes utilizing 19F chemical shifts as sensitive electronic probes.[1]. As stated previously[6], the basic philosophy behind this approach is that if there is good agreement between the theoretical and experimental relative shielding effects, confidence might be placed in an NBO analysis to provide molecular parameters which reveal the electronic interactions perturbing the local environment of the fluorine nucleus With this in mind, in order to validate the calculated 19F SCS of 9 and 10 we report the 19F SCS of a limited number of these larger systems (X=F, Cl, Br, I, OH, CH3, and Sn(CH3)[3]). A brief account was given in our earlier studies. 6

Results and Discussion

NO2 CN COOH COOCH3 CONH2

Conclusions