Transcript Organic Chemistry Chapter 1

Organic Chemistry
Chapter 8
Part I
Ethers
Nanoplasmonic Research Group
Ethers and Epoxides (What ?)
• Ethers: Compounds that have two
organic groups connected to a single
oxygen atom
• Epoxides: Cyclic three-membered ring
ethers
Ethers (how to name ?)
• IUPAC system: the general formula
“alkoxyalkane”
2-methoxypentane
trans-2-methoxycyclohexanol
1,3,5-trimethoxybenzene
• Trivial name: Describing two alkyl
groups and appending “ether”
ethyl methyl ether
diethyl ether (the prefix
dis-is sometimes omitted)
diphenyl ether
Ethers (physical properties)
• A relatively low boiling point: compared
to that of the analogous alcohols: No
hydrogen bonds amongst each other
(page 236)
• Water-soluble: two lone pairs of electrons
on the oxygen atoms makes hydrogen
bonding with water molecule possible
(page 237)
• Lewis bases: can coordinate to
magnesium in Grignard reagents and
boron compounds
One quick question!!
• If you are given to synthesize C-C bond,
then how to make it ?
There are two options
C
C
Free radical reaction
C- C+
We all know how to generate carbocation,
but what about C-???
The Grignard Reagent (I)
• Nucleophilic carbon!!!!: carbanion
• Organometallic chemical reaction in
which alkyl- or aryl- magnesium halides
(Grignard reagents), act as nucleophiles,
attack electrophilic carbon atoms that are
present within polar bonds (e.g., carbonyl
group)
The Grignard Reagent (II)
• Important tool in the formation of
carbon-carbon bonds, carbon-silicon,
carbon-boron, and other carbonheteroatom bonds
• The addition of the GR reagent to the
carbonyl typically proceeds through a sixmembered ring transition state
Ethers in the GR (solvent!!)
• Acting as a Lewis base, ether stabilizes a
Grignard reagent
• Carbanions are strong bases: Thus, most
Grignard reactions occur in solvents such
as anhydrous diethyl ether or THF
Preparation of Ethers
• Intermolecular Dehydration of Alcohols:
Effective for making symmetric ethers,
why?
• Nucleophilic Displacement of Alkyl
Halides by Alkoxide (Williamson ether
synthesis: treatment of alcohols with
strong bases!!!)
• Electrophilic Addition of Alcohols to
Alkenes