STRUCTURAL-ANALYSIS OF 2,2,4,4-TETRAMETHYL PENTANE

For the normal alkanes the structures of the most stable conformations are well known. They correspond to the all-trans configurations follo wing what is often referred to as the ''pentane rule''. However the br anched alkanes have received much less attention and their equilibrium structures are not predictable. The branched nonane isomer 2,2,4,4-te tramethyl pentane is a special case as the steric hindrance of the two equivalent tert-butyl groups is very great. The results of this work provide a quantitative evaluation of this intramolecular interaction, as well as a determination of the parameters necessary to establish th e structure of this molecule in its most stable form. The most signifi cant result is the opening of the central C-C-C angle by 15 degrees wi th respect to the usual tetrahedral value of 109.47 degrees.