OChem2Ch13

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victimsofadown
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207257
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OChem2Ch13
Updated:
2013-03-15 02:30:31
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OChem2Test2
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OChem2Ch13
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  1. Alcohol nomenclature
    • Name as standard alkene/alkyne
    • Replace -e with -ol and indicate the position of the C containing the O
    • example - 2-hexanol
  2. Physical properties of alcohols
    • Boiling point much higher than similar MW hydrocarbons due to H bonding
    • Low MW alcohols miscible in water, pentanol+ are not
  3. dDeprotonating alcohols
    • Alcohol is on the acidic side, but not highly acidic
    • Strong Base: Need a strong base OR base that can't form equilibrium (NaH, the H2 will evaporate)
    • Na, Li, K: Also cause the H2 to evaporate
    • Phenol is much more acidic than other alcohols (conj base highly stablized)
    • NaOH will deprotonate phenol
  4. Factors affecting acidity of alcohol
    • 1. Resonance:
    • 2. Induction: highly electronegative groups
    • 3. Solvation effects: Solvent helps to stabilize (less substituted alcohol will be more stabilized - steric hinderence)
  5. Preparation of alcohols - substitution reactions
    • RCH2Cl + NaOH --SN2-> RCH2OH + NaCl
    • RC(CH3)2Cl + H2O --SN1-> RC(CH3)2Cl + HCl

    2° alkyl halides do not work well (SN1 too slow, SN2 favors elimination)
  6. Preparation of alcohols - addition reactions
    • CH3-CH=CH2 undergoes the following rxns..
    • Markovnikov
    • H2SO4,H2O: CH3-CH(OH)-CH3
    • 1)Hg(OAc)2,H2O 2)NaBH4: CH3-CH(OH)-CH3
    • Anti-Markovnikov
    • 1)BH3*THF 2)HOOH, NaOH: CH3-Ch2-Ch2-OH
  7. Oxidation vs reduction
    • Oxidation: addition of bonds to O OR removal of bonds to H (oxidation # increases)
    • Reduction: addition of bonds to H OR removal of bonds to O (oxidation # decreases)
    • Oxidation #: Count e- around atom vs valence (which atom is more electronegative?)
  8. Preparations of alcohols - reduction (not COOH)
    • Ketone --red-> 2° alcohol
    • Aldehyde --red-> 1° alcohol
    • Formaldehyde --red-> methanol

    • Reducing agents:
    • Will reduce C=O and C=C:
    • H2 in presence of catalyst
    • Selective.  Will reduce C=O and leave C=C:
    • NaBH4 in EtOH, MeOH, or H2O
    • LAH is much more reactive than NaBH4 but VERY water sensative (no protic solvents), requires 2 steps
  9. Carboxylic acid/Ester reduction
    • RCOOH
    • 1) LAH, ex 2)H2O: R-CH2OH
    • NaBH4: no rxn
    • RCOOR
    • 1) LAH, ex 2)H2O: R-CH2OH + HOR
    • NaBH4: no rxn
  10. Diol nomenclature
    • Must include chain with both OH groups
    • Name as alkane -e +diol
    • Example - 2,3-hexanediol
  11. Making diols
    • From diketones:
    • H2,Pt: diol
    • 1)LAH 2)H2O: diol
    • 1)NaBH4 2)MeOH: diol

    • From alkene
    • OsO4,NMO: cis diol [syn addition]
    • 1)RCO3H 2)H2O: trans diol [anti addition]
  12. Preparation of alcohols - Grignard reagant
    • R-X --Mg->  R-Mg-X
    • Ph-Br --Mg-> Ph-Mg-Br
    • *C-Mg bond gives C a negative charge which attacks the C=O of ketones/aldehydes
    • Product is an alcohol + R group.  VERY IMPORTANT
    • Water must be added separately (even moisture will destroy the gignard reagant).
    • ketone: 3° alcohol + R (same C)
    • aldehyde: 2° alcohol + R (same C)
    • Ester: 3° alcohol + R + R (same C)
    • Carboxillic acid: WILL NOT WORK (protic)
  13. Protection of OH group
    *Grignard can't form if OH is on the attempted reagent

    • 1. Remove the H from OH group, replace with "protecting group" that will allow Grignard reagent to form
    • RO-H --TMSCl,Et3N-> RO-TMS
    • 2. Form Grignard reagent, perform rxn
    • 3. Deprotect, converting protecting group to -OH again
    • RO-TMS --H30+ OR F--> RO-H

    *F- typically donated by TBAF
  14. Reactions of alcohols - substitutions
    • 1°OH
    • HBr: 1°Br + H2O (SN2)
    • HCl, ZnCl2: 1°Cl + H2O (SN2)
    • SOCl2,py: 1°Cl (SN2)
    • PBr3: 1°Br (SN2)

    • 2°OH
    • 1)TosCl, pyrimidine 2)NaBr: 2°Br (inversion of config) (SN2)
    • SOCl2,pyrimidine: 2°Cl  (inversion of config) (SN2)
    • PBr3: 2°Br (inversion of config) (SN2)

    • 3°OH
    • HX: 3°X + H2O (SN1)
  15. Reactions of alcohols - elimination
    • 3°OH
    • H2SO4: 2x bond where C-OH was (E1)
    • 1)TosCl,Et3N 2)NaOEt,EtOH: 2x bond where C-OH was (E2)
  16. Oxidation of alcohols
    • 1° Alcohol -> Aldehyde -> Carboxylic acid
    • 2° Alcohol -> Ketone
    • 3° Alcohol -> N/A

    H2CrO4 OR H2Cr2O7,H2SO4,H20 OR CrO3,H3O+ will perform a full oxidation

    PCC,CH2Cl2 can perform a single-step oxidation

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