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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.
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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)
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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+
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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
- HydrogenationC=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
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Reactions of ethers
Unreactive to base or mild acid
- React to strong acid (SN2)
- CH3OCH3 --HX-> CH3X + CH3X + H2O
- Phenyl ethers can't do SN2 displacement
- PhOCH3 --HX-> PhOH + CH3X
- Autooxidation of ethers (not desired)
- OO inserted between CH bond at α position
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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
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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
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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)
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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
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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
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Sulfide
- Contain R-S-R'
- Named as ether (common), but using "sulfide" not "ether"
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