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Organic Chemistry > Ethers and Epoxides. > Flashcards

Ethers and Epoxides. Flashcards

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1
Q

What is the bond angle of water?

A

105 Degrees.

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2
Q

What is the bond angle of methanol?

A

108.5 Degrees.

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3
Q

What is the bond angle of dimethyl ether?

A

112 Degrees.

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4
Q

What is the bond angle of di tert butyl ether?

A

132 Degrees.

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5
Q

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

A

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

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6
Q

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

A

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

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7
Q

Do ethers have hydrogen bonding?

A

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

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8
Q

What is an ether?

A

R-O-R.

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9
Q

Are ethers soluble in water?

A

Yes.

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10
Q

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

A

A primary alcohol.

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11
Q

Epoxide + LiAlH4 gives what?

A

An alcohol.

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12
Q

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

A

The less substituted carbon.

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13
Q

Are ethers symmetrical or unsymmetrical?

A

They can be both.

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14
Q

What molecular geometry do ethers have?

A

Bent.

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15
Q

The oxygen on an ether has what hybridisation?

A

SP3.

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16
Q

What is a heterocyclic ether?

A

The oxygen is part of the ring.

17
Q

What is the Williamson Ether synthesis?

A

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

18
Q

What is a alkoxymercuration–Demercuration Reaction?

A

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

19
Q

Why are ethers good solvents?

A

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

20
Q

How can ethers be cleaved?

A

They can be cleaved by heating with HBr and HI.

21
Q

What is more reactive, HI or HBr?

A

HI.

22
Q

How does a phenyl ether cleavage work?

A

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.

23
Q

What are sulfides?

A

R-S-R.

24
Q

How are thiolates synthesised?

A

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

25
Q

How are epoxides synthesised?

A

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.

26
Q

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

A

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

27
Q

What are crown ethers?

A

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

28
Q

What are oxetanes?

A

These are four membered rings with one oxygen.

29
Q

What are furans?

A

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

30
Q

What are pyrans?

A

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

31
Q

What are dioxanes?

A

These are six membered rings with two oxygens.

32
Q

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

A

Cleavage and oxidation.

33
Q

Ether cleavage produces what?

A

An alcohol and an alkyl halide.

34
Q

Phenyl ethers cleave to give what?

A

Alkyl halides and phenols.

35
Q

Why does the reaction stop at the phenol stage?

A

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.

36
Q

What is one of the most common epoxidising reagents?

A

MCPBA

37
Q

What reagents will attack ethers and epoxides?

A

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

Organic Chemistry (9 decks)

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