endo,endo-Tetra-cyclo-[6.2.1.1(3,6).0(2,7)]dodeca-9-en-anti-11-yl 4-bromo-benzoate.

The title compound 1-OPBB, C(19)H(19)BrO(2), contains a dechlorinated and hydrogenated isodrin backbone with an anti-4-bromo-benzoate substituent at one of the methano bridges. The dihedral angle between the CO(2) ester plane and the benzene ring plane is 8.5 (2)°. In the crystal, the ester groups stack over benzene rings: the mol-ecules pack as conformational enanti-omers, with nearest parallel benzene ring planes separated by a perpendicular distance of 3.339 (1) Å. The nearest benzene-ring centroids are 5.266 (1) Šapart. Possible structural correlation with enhanced solvolytic reactivity is investigated.

Bicyclo-[2.2.1]hept-2-en-7-yl 4-bromo-benzoate.

The structure of the title compound, C(14)H(13)BrO(2), which contains a norbornenyl group and a 4-bromo-benzoate ester at the single C-atom bridge, has been redetermined [see McDonald & Trotter (1965 ▶). Acta Cryst.19, 456-463] to modern standards to establish high-precision geometrical data to compare with norbornyl and other tetra-cyclic 4-bromo-benzoates. Possible structural evidence is sought to help explain solvolytic reactivities.

Bicyclo-[2.2.1]hept-7-yl p-bromo-benzoate.

The title compound, C(14)H(15)BrO(2), contains a sterically unencumbered norbornyl group. The dihedral angle between the plane of the carboxyl-ate group and the mean plane of the adjacent benzene ring is 5.3 (2)°. The dihedral angle between the plane of the carboxyl-ate group and the norbornyl methano C-O bond is 4.5 (1)°, the methano C atom deviating by 0.141 (2) Šfrom this plane. In the crystal, mol-ecules pack as pairs of enanti-omers, with a distance of 3.747 (1) Šbetween the centroids of nearest parallel benzene rings.