O Chem 1

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Author:
napoleon
ID:
25530
Filename:
O Chem 1
Updated:
2010-07-15 16:30:23
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Chem CLO
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Description:
Organic Chemistry - Class 1
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  1. Acid:
    dissociates to give H+

    donates H+/proton

    e- acceptor
  2. Base:
    dissociates to give OH-

    accepts H+/proton

    e- donor
  3. Nucleophile:
    • unshared e- pair/ π bond
    • - /neg charge
    • "nucleus-loving"
    • lewis charge
  4. What makes a good nucleophile?
    • stronger -/neg charge, higher nucleophilicity;
    • basicity incr so does nucleophicity;
    • ↑basicity = ↑nucleophilicity
  5. Electrophile:
    • +/pos charge
    • "electron loving"
    • lewis acid
    • incomplete octet
  6. INDUCTION:
    • sharing e- through covalent b.
    • electronegative = electron withdrawing
    • not electronegative = electron donating
    • * alkyl gr --> electron donating
    • (alkyl -- alkane missing one H ; smallest methyl CH3-)
  7. e- donating gr =
    • give e- density to bond
    • = more basic = less acidic
  8. e- withdrawing gr =
    • take away e- density from bond
    • = less basic = more acidic
  9. RESONANCE:
    - more stable by spreading charge

    *delocalization: moving electrons b/w p-orbitals incr stability
  10. - Rules of Resonance -
    • 1. can only go through p orbitals
    • 2. can only move through lone pairs or π bonds
    • 3. + charges end up on the non-electroneg atoms
    • 4. - charges end up on electroneg atoms
  11. INTERMEDIATES
    - the more stable intermed, easier for rxn to occur

    - stabilize through induction

    - degree of substitution refers to the # of substituents on an atom
  12. 2 types of intermediates:
    • electron poor: carbocations - cabonium
    • radicals

    electron rich: carboanions
  13. HYDRIDE SHIFT
    move H- : to form more stable (more stable 2o subst --> 3o subst)

    • ONLY CARBOCATIONS
  14. METHYL SHIFT
    • (ONLY WKS W/ CARBOCATIONS)
  15. * Rules for determine R & S *
    • 1. Assign priority based on atomic #
    • - heavier isotope 1st
    • - same atom, move one out
    • - break apart multiple bonds

    2. Move the 4th group into back

    • 3. Go 1 → 2 → 3
    • CLOCKWISE R
    • COUNTER S

    4. If you had to do step 2, switch R → S or S → R
  16. Enantiomers:
    • - all chiral centers are opposites
    • - come in pairs
    • - > 1 chiral centers
    • - optical activity, same magnitude
    • opposite sign
    • - all other properties the same
    • - resolution way to separate them
    • - 50/50 mixture = RACEMIC MIXTURE
  17. Meso compounds:
    • - 1 line of symmetry & EVEN # OF CHIRAL
    • - no optical rotation
  18. Diastereomers:
    • - some but not all chiral centers are opposite
    • - 2 or more molecules
    • - separate via fractional distillation
  19. Substitution Rxn -- SN2
    substitution nucleophilic 2 bimolecular (2nd order)

    • [SN --> happens all at once]
    • SN2 --> chick (base) wants guy, girl sneaks in & kicks out other
  20. Principles SN2:
    • 1. reactivity based on steric hindrance
    • methyl > 1o > 2o > 3o

    2. solvent -- aportic (have Nu - want to remain unstable)

    • 3. Inversion of stereochemistry
    • R → S
    • S → R
  21. SN1
    unimolar (1st order)

    • [SN --> happens all @ once]
    • SN1 guy is (base) waits for guy to leave & go in
  22. Principles SN1:
    • 1. Based on stability of carbocation
    • 3o > 2o > 1o > methyl

    2. Solvent: protic

    3. Get RACEMIC mixture

    4. Shifts can occur
  23. Elimination rxn -- E1
    - incr bond order

    • E1--> waits to come off
  24. Principles of E1:
    • 1. Reactivity based on carbocation stability
    • 3o > 2o > 1o > methyl

    2. Polar protic (stabilize hylide/ leaving gr from attacking again)

    3. TRANS is more stable

    4. Shifts can occur

    5. Need β-hydrogen
  25. E2:
    occurs w/ alkyl halide ONLY

    • E2 --> all @ one time
  26. Principles E2:
    1. Reactivity based on sterics of base (more constituents is better, not always)

    • 2. Large base → least substituted
    • Small base → more substituted

    3. No shifts

    4. *Must be anti to the leaving gr
  27. How to favor E rxn over SN rxn...
    1. HEAT: ↑ heat gives reactants enough energy to overcome the increased Ea

    2. STRONG BASE: eliminations rxn use bases, not nucleophiles

    3. 3o OR 2o: Both E rxn prefer 3o substitution & are minimally affected by sterics
  28. E/SN Chart

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