Ethers and Epoxides.

Question 1

What is the bond angle of water?

Answer 1

105 Degrees.

Question 2

What is the bond angle of methanol?

Answer 2

108.5 Degrees.

Question 3

What is the bond angle of dimethyl ether?

Answer 3

112 Degrees.

Question 4

What is the bond angle of di tert butyl ether?

Answer 4

132 Degrees.

Question 5

Are the boiling points of ethers closer to alkanes or alcohols?

Answer 5

The boiling points of ethers are closer to alkanes than alcohols.

Question 6

What are the major contributors in the bonds of ethers, dipole dipole or dispersion forces?

Answer 6

The dipole-dipole attractive forces are minor contributors. The dispersion forces are the major contributors to intermolecular attractions.

Question 7

Do ethers have hydrogen bonding?

Answer 7

Ethers do not have OH groups hence the reason for the lack of hydrogen bonding.

Question 8

What is an ether?

Answer 8

R-O-R.

Question 9

Are ethers soluble in water?

Answer 9

Yes.

Question 10

When a Grignard reagent reacts with ethylene oxide, what is produced?

Answer 10

A primary alcohol.

Question 11

Epoxide + LiAlH4 gives what?

Answer 11

An alcohol.

Question 12

When a Grignard reagent reacts with ethylene oxide the attack takes place on which carbon?

Answer 12

The less substituted carbon.

Question 13

Are ethers symmetrical or unsymmetrical?

Answer 13

They can be both.

Question 14

What molecular geometry do ethers have?

Answer 14

Bent.

Question 15

The oxygen on an ether has what hybridisation?

Answer 15

SP3.

Question 16

What is a heterocyclic ether?

Answer 16

The oxygen is part of the ring.

Question 17

What is the Williamson Ether synthesis?

Answer 17

This method involves an SN2 attack of the alkoxide on an unhindered primary halide or tosylate.

Question 18

What is a alkoxymercuration–Demercuration Reaction?

Answer 18

Use mercuric acetate with an alcohol. The alcohol will react with the intermediate mercurinium ion by attacking the more substituted carbon.

Question 19

Why are ethers good solvents?

Answer 19

Ethers are unreactive, which makes them ideal solvents for a lot of different reactions.

Question 20

How can ethers be cleaved?

Answer 20

They can be cleaved by heating with HBr and HI.

Question 21

What is more reactive, HI or HBr?

Answer 21

HI.

Question 22

How does a phenyl ether cleavage work?

Answer 22

An alcohol is formed on the phenyl group as Phenol cannot react further to become halide because an SN2 reaction cannot occur on an sp2 carbon.

Question 23

What are sulfides?

Answer 23

R-S-R.

Question 24

How are thiolates synthesised?

Answer 24

Thiolates are easily synthesized by the Williamson ether synthesis, using dithiolate as the nucleophile.

Question 25

How are epoxides synthesised?

Answer 25

Peroxyacids are used to convert alkenes to epoxides. Most commonly used peroxyacid is meta-chloroperoxybenzoic acid (MCPBA). The reaction is carried out in an aprotic acid to prevent the opening of the epoxide.

Question 26

How will ethers enable unstable molecules to be used as reagents?

Answer 26

Ethers will often form complexes with molecules that have vacant orbitals, enabling ‘unstable’ molecules to be used as reagents.

Question 27

What are crown ethers?

Answer 27

Crown ethers are macrocyclic ethers, which help to solvate metal cations, and thus allow inorganic salts to dissolve in organic solvents.

Question 28

What are oxetanes?

Answer 28

These are four membered rings with one oxygen.

Question 29

What are furans?

Answer 29

These are five membered rings with one oxygen and two double bonds.

Question 30

What are pyrans?

Answer 30

These are six membered rings with one oxygen and two double bonds.

Question 31

What are dioxanes?

Answer 31

These are six membered rings with two oxygens.

Question 32

What are the 2 types of reactions that ethers can undergo?

Answer 32

Cleavage and oxidation.

Question 33

Ether cleavage produces what?

Answer 33

An alcohol and an alkyl halide.

Question 34

Phenyl ethers cleave to give what?

Answer 34

Alkyl halides and phenols.

Question 35

Why does the reaction stop at the phenol stage?

Answer 35

The reaction stops at the phenol stage since the sp2 carbon of the C-OH bond does not allow the required SN1 or SN2 reactions to generate the second molecule of aryl halide.

Question 36

What is one of the most common epoxidising reagents?

Answer 36

MCPBA

Question 37

What reagents will attack ethers and epoxides?

Answer 37

Grignard and organolithium reagents also attack epoxides at the least hindered carbon to generate alcohols.