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Tutorial topics: Introduction Viewing Basics Molecular Shapes (VSEPR) Conformations Ethane Butane Cycloalkanes Substituted Cyclohexane Sterochemistry SN2 Reaction SN1 Reaction Aromaticity

Conformations of Ethane In this tutorial, we will learn the relative stability of ethane conformations as a result of single bond rotation. The structure of ethane, C2H6, is shown below. The bond between the two carbon atoms is a single bond which is formed by two sp3 hybrid orbitals overlapping head to head. This symmetric cylindrical electron distribuation allows for "free" rotation around the C-C bond. Shown to the right of this structure are "live" ethane molecules animated to rotate around that bond, with the right one viewed from the left the molecule.   a single sigma C-C bond Ethane viewed from the top viewed from the left, with your eye looking down C-C bond As the C-C bond rotates, an infinite number of conformations (or conformers) is created. The two which are of most interest to us are shown below: Ethane Conformation A Rotate Me! Ethane Conformation A Rotate Me! It's now your turn to rotate the two conformers and examine their spatial properties. After that, answer the following two questions: 1) which is of lower energy and thus more stable? 2) What are the names we give to the two conformers? (hint: how are the hydrogens arranged on the front carbon relative to the back carbon?)