Ethers

Nanoplasmonic Research Group

Organic ChemistryChapter 8

Part I

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 ?)

• Trivial name: Describing two alkyl groups and appending “ether”

2-methoxypentanetrans-2-methoxycyclohexanol 1,3,5-trimethoxybenzene

• IUPAC system: the general for-mula “alkoxyalkane”

ethyl methyl ether diethyl ether (the prefixdis-is sometimes omitted)

diphenyl ether

Ethers (physical properties)• A relatively low boiling point: com-

pared to that of the analogous al-cohols: No hydrogen bonds amongst each other (page 236)

• Water-soluble: two lone pairs of electrons on the oxygen atoms makes hydrogen bonding with wa-ter 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

C- C+

Free radical reaction

We all know how to generate carbo-cation, 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-sili-con, carbon-boron, and other car-bon-heteroatom bonds

• The addition of the GR reagent to the carbonyl typically proceeds through a six-membered ring tran-sition state

Ethers in the GR (solvent!!)

• Acting as a Lewis base, ether stabi-lizes 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 Al-

cohols: Effective for making sym-metric ethers, why?

• Nucleophilic Displacement of Alkyl Halides by Alkoxide (Williamson ether synthesis: treatment of alco-hols with strong bases!!!)

• Electrophilic Addition of Alcohols to Alkenes