Hyperconjugation+Extra+Credit

Hyperconjugation not steric repulsion leads to the staggered structure of ethane Pophristic, Vojislava, and Lionel Goodman. "Hyperconjugation Not Steric Repulsion Leads to the Staggered Structure of Ethane." //Nature//. Nature Publishing Group. Web. 12 Mar. 2012. .
 * In the text book example of ethane, two methyl group will rotate around a central carbon
 * Alternates three times between the unstable eclipsed conformation and most stable staggered conformation
 * Usually the preferred conformation was attributed to steric hindrance
 * As ethane rotates toward the eclipsed conformation the electrons on the different C-H bonds experienced increased repulsion
 *  Instead, the author proposes stabilization of the staggered structure through rotation-induced weakening of the central C-C bond and hyperconjugation
 * Test removal of different interaction
 * Hyperconjugation
 * Electron transfer from an occupied to an unoccupied orbital leading to delocalization of charge
 * Steric Factor
 * Exchange
 * Uses Pauli exclusion principle which states that pairs of electrons not to occupy the same spatial region
 * Electrostatic
 * Also known as Coulomb interaction
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Different than exchange because works over long range
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Potential curves in terms of torsional angle
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">First curve with all interactions present representing the energy of the real system
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Second with the energy of the system with exchange repulsion absent
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Concludes that minima of both curves prefer the staggered configuration regardless of exchange repulsion
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Tests for hyperconjugation in terms of examining the internal rotation-induced change in nuclear electron attraction via molecular orbitals
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Potential energy measured in ∆Vne and split between σ and π contributions
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">In ethane only two types of hyperconjugation exist
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">vicinal (between methyl groups)
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Only π orbitals overlap
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">geminal (within a single methyl group)
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Natural Bond Orbitals are used to further analyze interactions
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Doubly Occupied
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Hyperconjugation is expressed by electron transfer
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Staggered conformation is lost on removal of all charge transfers
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Shows that vicinal charge transfer interactions are the ones that keep the molecule in the staggered conformation
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">No inversion of structure occurs on removal of coulombic and exchange repulsions