Chem301 Ch4 USD

  1. Saturated hydrocarbons
    also called alkanes:
  2. Names of Alkanes
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    Find the longest chain
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  4. Number of isomers per alkane
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  5. Industrial uses for petroleum fractions
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  6. Hybridization of Carbons: the hybridization of carbon in alkanes is___________.
  7. The ideal bond angles for this set ofhybrid orbitals is_____.
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    Which is the most stable?
    Which is the least stable?
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  9. What factors affect stability?
    • Ring Strain
    • Angle Strain
    • Steric Strain
    • Torsional Strain
  10. Ring Strain
    The term applied to the strain of cycle sysytems. It is composed of Angle strain  and Steric (specifically torsional) strain.
  11. Angle Strain
    Is the potential energy stored in a molecule due to the deviation of the bond angles from their ideal values.
  12. Steric Strain
    results from the electron-electron repulsion of atoms (or groups of atoms) that are too close together. Steric strain stores potential energy in a molecule by repelling groups together.
  13. Torsional Strain
    is steric strain that occurs when there are eclipsed or gauche interactions.
  14. Cyclobutane angles are ______.
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    6-(2-methylbutyl) undekane
  16. Names of substituents with carbon chains.
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  17. What is the most stable form of of an 8 Carbon chain?
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  18. Physical properties of some Unbranched Alkanes
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  19. Staggered  and eclipsed conformation
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  20. Staggered Confermation - Anti:
    • The conformation when the largest substitutes on the two carbons possess a dihedral angle of 180o.
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  21. Staggered Conformation - Gauche:
    • The conformation when the largest substituents on the two carbons possess a dihedral of 60o.
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  22. Conformation Analysis: Energy Costs
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  23. What does a flagpole intersection look like?
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  24. Cyclohexanes
    • Cyclohexane is considered to have ZERO ring strain in its optimal conformation, which is called the CHAIR conformation.
    • No angle strain - angles must be 109.5o.
    • No torsional strain - all adjacent C - H bonds must be staggered.
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    • Cyclohexane exits in other conformations but they are less stable. Consider one of these conformations, the BOAT conformation.
    • No angle strain - angles are 109.5o.
    • Torsional strain - 4 pairs eclipsing C - H.
    • Steric Strain - flagpole interactions from the proximity of the H atoms on the carbons puckered out of the plane.
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  25. Energy for different cyclohexane structures
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  26. Drawing a cyclohexane CHAIR conformation.
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  27. Drawing cyclohexane CHAIR Conformation: the substituents
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  28. Monosubstituted Cyclohexanes
    • The vast majority of cyclohexane molecules will exist in the chair conformation at any given moment.
    • When energy (45 KJ/mol) is available, cyclohexane can flip from one chair form to another.
    • If both versions of the CHAIR were equally stable, you would have a 50/50 mixture of axial/equatorial.
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    • The flipping a chair is actually the result of C - C single bonds rotating ONLY.Image Upload 23
  29. Monosubstituted Cycloalkanes:
    Comparison to NEWMAN projection GAUCHE and ANTI conformations
    • When the substituent is in the axial position, the 1,3-diaxial interactions are equivalent to GAUCHE interactions:
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    • When the substituent is in the equatorial position, it is equivalent to an anti interaction.Image Upload 25
  30. Larger groups will causemore steric crowding in the axial position.
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  31. Must be careful to consider 3D orientation, configuration, of each substituent.
    Consider 1-chloro-2-methylcyclohexane. What configuration will it adopt/prefer?
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    • First: notice that the chlorine atom remains UP in each chair configuration and the methyl group remains down.
    • Flipping does not result in a configuration (i.e. UP substituents remain UP and DOWN remain DOWN).
  32. Diamond
    • Fused six-membered rings locked in chair conformations.
    • Depiction below is a portion of diamond - it extends essentially infinitely in all three dimensions.
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  33. Possible Newman structures for propane
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  34. Draw Newman projection of the following compounds
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Card Set
Chem301 Ch4 USD
general terms and definitions text book "Organic Chemistry" University of San Diego/ Klein: copyright 2012 John Wiley & Sons, Inc. sigma bonds, pi bonds, ionic bonding, covalent bonding, basics, histories