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1.2 Organic Chemistry > Ethers > Flashcards

Ethers Flashcards

1
Q

What are ethers?

2

A

A class of organic compounds containing an O atom bonded by a single bond to two alkyl and or aryl groups

The two alkyl/aryl groups can be the same or different

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2
Q

What is the O in ethers bonded to?

A

To two alkyl and/or aryl groups

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3
Q

What type of bond is found between the O and the alkyl/aryl groups in ethers?

A

A single group

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4
Q

What is an alkyl group?

A

Its an alkane with a hydrogen atom missing from its chain

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5
Q

What is the general formula of an alkyl group?:

A

Cn H(2n+1)

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6
Q

What is the smallest alkyl group?

A

The methyl group (CH3)

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7
Q

What is an aryl group?

A

A simple aromatic compound with one of its hydrogen atoms missing (this missing atom allows the molecule to attach to a carbon chain)

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8
Q

Give an example of an aryl group.

A

Tolyl group (derived from toluene - a benzene ring with the substitution of a methyl group)

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9
Q

How are ethers named if both of their groups are alkyl groups?

A

The ether is usually named as alkyl aklyl ether

The alkyl groups are listed in alphabetical order

If the two alkyl groups are the same then it’s a dialkyl ether

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10
Q

Give an example of a dialkyl ether.

A

Dimethyl ether (an O singly bonded to two methyl groups - CH3)

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11
Q

When naming an ether with two alkyl groups, how do you decide the order of naming the alkyl groups?

A

The alkyl groups are listed in alphabetical order

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12
Q

How do you name an ether which has two of the same alkyl groups?

A

Dialkyl ether

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13
Q

How is an ethyl group written in an ether?

A

CH3 CH2

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14
Q

How do you go about naming intermediate ethers?

A

You treat the ether group as an alkoxy group

The root name is defined by the more complex group i.e. longer chain

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15
Q

What is the formula for methoxy?

A

CH3O

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16
Q

What is the name given to CH3CH2O?

A

Ethoxy

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17
Q

What exactly is an intermediate ether?

A

An ether where there is one complex group

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18
Q

What exactly is a complex ether?

A

An ether where there is two complex group

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19
Q

How do you name a complex ether?

A

Ether is treated as a chain substituent and given the prefix oxa

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20
Q

What three factors affect boiling point?

3

A

Relative strength of intermolecular forces; coulombic forces > dipole forces > induced dipole forces

B.p increases with increasing molecular mass i.e. number of C atoms and FGs present

Molecular symmetry or lack thereof - b.p. decreases with branching

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21
Q

List the intermolecular forces in order of increasing strength.

A

Ionic > H-bonding > Dipole-dipole > induced dipole - induced dipole

22
Q

What is the relationship between a compound’s molar mass and boiling point?

A

Boiling point increases with molecular mass i.e. the number of C atoms anf FGs present

23
Q

What is the relationship between molecular symmetry and boiling point?

A

Boiling point decreases with branching

Symmetrical molecules with no branching have higher boiling points

24
Q

How do the boiling points of ethers compare to that of alcohols with an equal number of C atoms?

A

Ethers have lower boiling points than these alcohols

25
Q

When will ethers undergo H-bonding?

A

The O of ethers will undergo H-bonding with H2O

26
Q

Are ethers soluble in water?

A

Only some ethers are soluble in water

27
Q

Which ethers are soluble in water?

A

Ethers that contain up to 3 carbon atoms due to their H-bond formation with water molecules

28
Q

What state are ethers in at room temperature?

2

A

Most are colourless volatile liquids with pleasant ether smells

Dimethylether and ethyl methyl ether are gases at ordinary temperature

29
Q

Describe the density of ethers.

A

Ethers are less dense than water -> float on water

30
Q

Describe the flammability of ethers.

A

Ethers are highly flammable - must not be used in presence of flame

31
Q

How are ethers synthesized?

A

By reacting alkyl halides (or other substrates which are good leaving groups) with an alkoxide ion in a substitution reaction

32
Q

What is an alkyl halide?

2

A

Haloalkanes

Alkane with one or more halogen

33
Q

What is an alkoxide ion?

A

The conjugated base (deprotonated form) of an alcohol

34
Q

Are alcohols nucleophiles or electrophiles?

A

Alcohols are weak nucleophiles

35
Q

Since alcohols are weak nucleophiles, what does this make alkoxide ions?

A

This makes them good nucleophiles

36
Q

Explain in your own words the substitution reaction that needs to take place to synthesise an ether.

A

A deprotonated alcohol is reacted with a haloalkane to form an ether

37
Q

What type of alkyl halide doesn’t work well to form an ether?

A

Secondary alkyl halides don’t work well

38
Q

How can the synthesis of an ether using a secondary alkyl halide reaction be improved?

A

A polar aprotic solvent such as dimethyl-sulphoxide (DMSO) can be used

39
Q

What type of alkyl halide cannot be used to form ethers?

A

Tertiary alkyl halides even with DMSO

40
Q

What can readily be given from an elimination reaction using a tertiary alkyl halide?

A

An alkene can be formed

41
Q

How are alkoxide ions formed from alcohols?

A

The alcohol is deprotonated by using a super strong base such as sodium hydride

42
Q

Why are ethers widely used as solvents?

A

Ethers are inert - very unreactive

43
Q

Most ethers are inert, what ethers are exceptions to this statement?

A

Epoxides

44
Q

What are epoxides?

A

Ethers that are highly reactive due to ring strain

45
Q

What is cleavage of a molecule?

A

The splitting of chemical bonds

46
Q

What is required for cleavage of ethers?

A

Harsh conditions e.g. strong acids

47
Q

What are the two steps in ether cleavage?

A

Protonation by a strong acid to generate a good leaving group

Then a substitution reaction by a decent nucleophile

48
Q

What happens when an ether is exposed to the air for a long time?

A

The ether may contain organic peroxides due to air oxidation which can be a safety hazard as they are explosive

49
Q

How are peroxides detected in ethers?

A

Using a dip-stick

50
Q

How are peroxides removed from ethers?

A

By shaking with aqueous ferrous sulfate (FeSO4)

1.2 Organic Chemistry (15 decks)

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