1 / 15

Organic Chemistry Chapter 2

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

gelsey
Download Presentation

Organic Chemistry Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Organic ChemistryChapter 2 Alkanes and Cycloalkanes Nanoplasmonic Research Group

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

  3. How to READ them ? • Systematic methods for naming compounds (IUPAC) • RULES (see page 44 middle ~ page 45) • 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

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

  5. 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)

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

  7. Conformational Energy of Ethane

  8. 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

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

  10. 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

  11. Cyclohexane

  12. DisubstitutedCyclohexane (I)

  13. DisubstitutedCyclohexane (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)

  14. The relationships of the various types of isomers

More Related