1. Alkanes and Cycloalkanes Nanoplasmonic Research Group Organic Chemistry Chapter 2

2. Fully-saturated hydrocarbons: Alkanes & Cycloalkanes Nanoplasmonic Research Group How to READ their structures: NOMENCLATURE Physical Properties: Interaction & Conformation Physical Properties: Interaction & Conformation Chemical Properties: Reactions

3. How to READ them ? Systematic methods for naming compounds (IUPAC) RULES (see page 44 middle ~ page 45) 1.Find out the longest continuous chain 2. Number the substituents 3. Write the name as one word If 2 different chains of equal length are present, choose the one with the greater number of branch points If the first branch points occurs at the same carbon number on both ends, begins at the end that has the second nearest branch pints Put the substituents in alpabetical order: di-, tri-, tetra-, sec-, tert-, ignored when alphabetizing, iso-, neo- are included when alphabetizing

5. How to read substituents ? Methyl, ethyl, propyl, etc Iso, sec-, tert-, etc Fluoro, chloro, bromo, iodo

6. Physical Properties: Intermolecular Interaction Nonpolar due to the fact that C-C & C-H bonds are nearly purely covalent (no dipole moment) Interaction between alkanes –Induced dipole-induced dipole moment –Van der Waals attraction –M.W. dependence Van der Waals interaction –Permanent dipole-permanent dipole forces (Keesom) –Permanent dipole-induced dipole forces (Debye) –Induced dipole-induced dipole forces (London)

7. Conformations of alkanes A consequence of rotating one carbon atom with respect to the other carbon atom

8. Conformational Energy of Ethane

9. Conformational Analysis Summary Torsional energy –Higher energy associated with eclipsed conformation Torsional strain –Resistantce to rotating to an eclipsed conformation Steric strain –Repulsive interactions that occurs when atoms are forced closed together than their atomic radii allow Gauche: spatial relationship with a 60 torsion angle Interactions –H-H eclipsing (torsional strain): 1.0 kcal/mol –H-Me eclipsing (mostly torsional strain) 1.4 kcal/mol –Me-Me eclipsing (steric and torsional strain) 2.6 kcal/mol –Me-Me gauche interaction (steric strain) 0.9 kcal/mol

10. Why is staggered form lower in energy Hyperconjugation –Stabilizing overlap between sigma bond and antibonding orbitals that does not occur in the eclipsed conformer Electron-electron repulsion Conformational Energy of Butane

11. Naming Cyclohexane Find parent (ring or chain, depending on which is larger) Label point of attachment of alkyl, halo, etc Continue numbering so that the second substituent is the lowest possible number If 2 or more groups could potentially get the same number, use alphabetical order as a tie-breaker

12. Cyclohexane

13. Disubstituted Cyclohexane (I)

14. Disubstituted Cyclohexane (II) If 2 substituents are on cyclohexane the lowest energy conformation –Has both substituents equatorial (if possible) –t-Bu is NEVER axial Cis-Trans Isomerism –Do not interconvert each other (see page 59 bottom)

15. The relationships of the various types of isomers