epoxide
- a three membered cyclic ether
- angle strain make epoxides particularly reactive
ether
a compound containing an oxygen atom bonded to two carbon atoms
-sp3 hybridized and sigma bonds, providing tetrahedra geometry
alkoxy group
an -OR group where R is an alkyl group
heterocycles
a cyclic compound whose ring contains more than one kind of atom
physical properties of ethers
weak dipole-dipole interaction; H-bond acceptors (not donors). Thus boiling points are lower than alcohols of similar molecular weight
Williamson ether synthesis
-SN2 reaction between a haloalkane and an alkoxide ion to produce an ether
acid catalyzed dehydration of alcohols
- best for primary, unhindered alcohols
- highest yields in forming symmetric ethers (start with one alcohol)
acid catalyzed additional of alcohol to Alkenes
-best for alkenes that form stable carbocations with primary alcohols
reactions of ethers
- like hydrocarbons, ethers are pretty unreactive, making them good solvents
- safety: very flammable solvent sand over time ethers react with oxygen to form hyper oxides, which are explosive
- ethers do not react under harsh acidic conditions
protecting group
a substituent that prevents a functional group from reacting while some other part of the molecule undergoes a desired transformation
-allow us to selectively transform parts of a molecule, while leaving protected functional groups intact
factors that make a good protecting group
- easy to add to the sensitive functional group
- resistant to the reagents used to transform parts of a molecule, while leaving protected functional groups
silyl ethers
- unlike alcohols, silyl ethers (R-O-Si) do not react with oxidants and non-aqueous acid and base
- can be formed and broken under very mild conditions
epoxides
cyclic ether where oxygen is one atom of a three membered ring - REACTIVE
internal nucleophilic substitution in Halohydrins reaction
- regioselective: -Br goes on the less substituted carbon, -OH goes on the more substituted carbon
- stereoselective: -Br and -OH add from the opposite face of the double bond (anti)
acid catalyzed ring opening
regioselective: -Nu goes on the more substituted carbon, -OH goes on the less substituted carbon
stereoselctive: -Nu performs backside attack, adding from the opposite side of the epoxide (anti)
nucleophilic ring opening
- regioselective: -Nu goes on the less substituted carbon, -OH goes on the more substituted carbon
- stereoselective: -Nu performs backside attack adding from the opposite side of the epoxide (anti)
sulfide
the sulfur analog of an ether; a molecule containing a sulfur atom bonded to two carbon atoms
