MOLECULAR MECHANICS STUDIES (MM3) ON THE CONFORMATIONS OF SOME DERIVATIVES OF TRIPTYCENE

Several derivatives of triptycene have been studied, wherein the substituent at the bridgehead can be directed in or out relative to the benzene rings, or wherein one of the benzene rings is substituted to make it different from the others, and a substituent can take up different conformations, depending on which pair of benzene rings the tails of the substituent chooses to lie between. The equilibria between the different conformations gives one a way to measure interactions between various kinds of substituents. Experimental results of this kind from the literature have been compared with the results of molecular mechanics. In some cases the experimental results are well calculated with MM3, and in some cases they are not. The latter cases are instructive, because they show shortcomings in our molecular model, which again in some cases are understood, but in other cases show a further shortcoming in our knowledge of chemistry.