Chapter 11 Notes

Question 1

epoxide

Answer 1

• a three membered cyclic ether

- angle strain make epoxides particularly reactive

Question 2

ether

Answer 2

a compound containing an oxygen atom bonded to two carbon atoms
-sp3 hybridized and sigma bonds, providing tetrahedra geometry

Question 3

alkoxy group

Answer 3

an -OR group where R is an alkyl group

Question 4

heterocycles

Answer 4

a cyclic compound whose ring contains more than one kind of atom

Question 5

physical properties of ethers

Answer 5

weak dipole-dipole interaction; H-bond acceptors (not donors). Thus boiling points are lower than alcohols of similar molecular weight

Question 6

Williamson ether synthesis

Answer 6

-SN2 reaction between a haloalkane and an alkoxide ion to produce an ether

Question 7

acid catalyzed dehydration of alcohols

Answer 7

• best for primary, unhindered alcohols

- highest yields in forming symmetric ethers (start with one alcohol)

Question 8

acid catalyzed additional of alcohol to Alkenes

Answer 8

-best for alkenes that form stable carbocations with primary alcohols

Question 9

reactions of ethers

Answer 9

• 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

Question 10

protecting group

Answer 10

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

Question 11

factors that make a good protecting group

Answer 11

• easy to add to the sensitive functional group

- resistant to the reagents used to transform parts of a molecule, while leaving protected functional groups

Question 12

silyl ethers

Answer 12

• 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

Question 13

epoxides

Answer 13

cyclic ether where oxygen is one atom of a three membered ring - REACTIVE

Question 14

internal nucleophilic substitution in Halohydrins reaction

Answer 14

• 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)

Question 15

acid catalyzed ring opening

Answer 15

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)

Question 16

nucleophilic ring opening

Answer 16

• 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)

Question 17

sulfide

Answer 17

the sulfur analog of an ether; a molecule containing a sulfur atom bonded to two carbon atoms