Polyfluorobicyclo[2.2.1]heptanes. Part X. Crystal and molecular structure of endo-1-methoxycarbonyl-3H,4H-nonafluoronorbornane

Abstract

X-Ray crystallographic analysis has established that the major product obtained from endo-1H,2H,4H-nonafluoronorbornane (I) by a series of reactions, the first of which is an electrophilic displacement using methyl-lithium, is endo-1-methoxycarbonyl-3H,4H-nonafluoronorbornane (III). The displacement reaction, therefore, takes place predominantly at the 4-position. A minor (ca. 7%) constituent of the crystal may have been formed via displacement at the other bridgehead position. Crystals are orthorhombic, space group Pna2₁, with Z= 4 in a cell of dimensions a= 13.78(1), b= 9.78(1), c= 7.985(10)Å. The structure was determined by direct methods and refined by least-squares techniques to R 3.8% for 1 079 observed reflections. The norbornane skeleton shows small but significant deviations from the ideal C_2v symmetry due to the unsymmetrical nature of the substitution.