Date of Award
Master of Arts
Masters Thesis-Open Access
The configuration of biphenyl has been treated in numerous articles and reviews (1, 5, 6, 7, 8, 16, 22, 23). In particular the configuration of 2,2'-bridged biphenyl derivatives has obtained attention. The synthesis of an optically active 2,2'-three-carbon-atom-bridged biphenyl possessing an ultraviolet absorption maximum at 250 mμ has been reported by Iffland and Siegel (15). These properties require first, a non-planar configuration for the molecule and second, significant inter-ring conjugation as demonstrated by ultraviolet spectra.
Several 2,2'-three-atom-bridged biphenyls have been prepared by Ahmed and Hall (2, 3) in order to obtain some measure of their specific rotation. The use of various 6,6' -substituents, larger than hydrogen, were employed to increase optical stability of the compounds studied.
Another approach to the problem was undertaken by Iffland and Chiang who utilized bulky 3,3'-substituents as buttressing agents upon the three-atom bridge (11). The resulting change in configuration and twist angle could then be studied with gradual changes in the size of the substituents. With chlorine as the buttressing agent the molecule revealed a configuration not unlike the unsubstituted compound.
The material initially prepared and identified as the 3,3'-diiodo analog failed to exhibit an absorption maximum in the 2.50 mμ region; this was considered dramatic evidence for a buttressing effect (11). However, reexamination of the synthesis of the diiodo compound demonstrated an error in the assignment of structure to the two products encountered (14). The ultraviolet spectrum of the true diiodo compound proved remarkably similar to that for the dichloro compound.
This work was undertaken before this assignment error was corrected and had as its objective the preparation of the analogous 3,3'dibromo compound to complete the 3,3'-dihalo-2,2'-three-atom-bridged biphenyl series.
Nader, "Preparation and Properties of 3, 3’ -disbubstituted-2, 2’ – Three-Carbon-Atom Bridged Biphenyls" (1963). Master's Theses. 4393.