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2013-03-15 05:22:21

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  1. Ether nomenclature
    • Common name: name both R groups and add "ether" at the end
    • Systematic: the smaller of the two R groups is named as an alkoxy substituted group
    • Remove -yl and add +oxy  (ethyl -> ethoxy)
    • The item will actually be names as an alkane w/ a functional group.
  2. Physical properties of ethers
    • sp3 hybridized, 112° separation (more than HOH and HOCH3)
    • H-Bond acceptors but NOT donors
    • BP lower than alcohol, but higher than Hydrocarbons
    • Commonly used as solvents (fairly unreactive, polar, low bp)
  3. Crown Ethers - nomenclature, purpose, etc
    • #atoms in ring - crown - #O in ring
    • Used to transport ions into solution.  Each size stabilizes a different cation, freeing the anion to go into the solution (usually F-).
    • 12-Crown-4: Li+
    • 15-Crown-5: Na+
    • 18-Crown-6: K+
  4. Preparation of Ethers
    • Industrial preparation of diethyl ether:
    • etOH+ H2SO4 <--> EtOEt
    • Acid catalyzed dehydration (SN2)
    • Only works well for 1° alcohols
    • Only produces symmetrical ethers

    • Williamson ether synthesis:
    • ROH --1)NAH 2)R'X-> ROR'
    • Step 1 alkoxide is formed
    • Step 2 alkoxide is nucleophile in SN2
    • STERICS in Step 2! 1°RX > 2°RX (3°RX won't work)
    • USE THIS INFORMATION TO DETERMINE WHICH R to use as alcohol and which to use as alkyl halide

    • Hydrogenation
    • C=C bond --H3O+,H2O-> C-OH
    • C=C bond --H3O+,CH3OH-> C-O-CH3
    • Typically only works w/ methyl/ethyl ethers

    • Alkoxymercuration-Demercuration:
    • C=C --1)Hg(OAc)2,ROH 2)NaBH4-> CH-R
    • Markovnikov addition across 2x bond
  5. Reactions of ethers
    Unreactive to base or mild acid

    • React to strong acid (SN2)
    • CH3OCH3 --HX-> CH3X + CH3X + H2

    • Phenyl ethers can't do SN2 displacement
    • PhOCH3 --HX-> PhOH + CH3X

    • Autooxidation of ethers (not desired)
    • OO inserted between CH bond at α position
  6. Epoxide nomenclature
    Oxirane is what we focus on C-O-C in triangle

    • Systematic: Name as alkane, and name epoxide as a subs group.  
    • Use BOTH C as locants.  
    • Name comes DIRECTLY BEFORE alkane name.
    • eg - 4,5-dimethyl-4,5-epoxydiene

    • Common name: name the epoxide then name the substituent
    • eg- 1-hexyl-1,2,2-trimethyloxirane
  7. Preparation of epoxides
    • Using Peracids
    • alkene --RCOOOH-> epoxide
    • MCPBA is most common peracid used
    • If there are functional groups the arrangement (cis or trans) is RETAINED

    • From halohydrin
    • alkene --1)Br2,H2O 2)NaOH-> epoxide
  8. Ring opening reactions of epoxides
    • oxirane reactions.
    • Reagents, and f(x) in R-CH2-CH2-OH
    • 1)RONA 2) H2O --> -RO
    • 1)NaCN 2) H2O --> -CN
    • 1)NaSH 2) H2O --> -SH
    • 1)RMgBr 2) H2O --> -R
    • 1) LAH 2) H2O --> -H

    • +NUC- attacks at less substituted position
    • +Inversion of configuration (trans between NUC and OH)
  9. Acid catalyzed ring opening of epoxides
    • oxirane reactions.
    • Reagents, and f(x) in R-CH2-CH2-OH

    • Acid catalyzed ring opening
    • HX --> -X
    • H3O+, ROH --> -OR
    • H3O+, H2O --> -OH

    • 1° and 2° attack is at less substituted position
    • 3° attack occurs at MORE substituted position
  10. Thiols
    • Contain -SH group
    • Named as alcohol, but using "-thiol" not "-ol"
    • When named as a functional group it is "mercapto"
    • Unpleasant odor like skunk
    • R-Br --NaSH-> R-SH + NaBr (inversion of configuration) (SN2)
    • Will work on 1° or 2° substrates
  11. Sulfide
    • Contain R-S-R'
    • Named as ether (common), but using "sulfide" not "ether"

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