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O Chem 2 > Ethers, Epoxides And Sulfides > Flashcards

Ethers, Epoxides And Sulfides Flashcards

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1
Q

Describe ethers

A

Have functional groups R—O—R’

They may be symmetrical or asymmetrical

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2
Q

What is the hybridization of the oxygen atoms in ethers?

A

Sp3

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3
Q

Describe the structure and angle of ethers

A

Ethers have a bent structure like water and C—O—C bond angle is about 110 degrees

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4
Q

Describe the polarity of ethers

A

Ethers contain a highly polar C—O despite not having the hydroxyl group of alcohols

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5
Q

Why are ethers useful as a solvent?

A

An ether e.g. tetrahydrofuran(THS) provides a strongly polar solvent without the reactivity of a hydroxyl group

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6
Q

Describe the bonding in pure ethers

A

Pure ether cannot engage in hydrogen bonding as they lack OH groups but they have large dipole moments which have little affect on boiling point

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7
Q

How can ethers engage in hydrogen bonding?

A

Can engage in hydrogen bonding with other compounds with O-H or N-H groups

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8
Q

Describe all of the reasons ethers are solvents in general

A
  • They dissolve in a wide range of polar and no polar substances
  • They easily evaporate from their reaction products because of their low boiling point
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9
Q

Why are no polar substances tend to more soluble in ethers than alcohols?

A

Because ethers have no hydrogen bonding network to be broken up by the no polar solute

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10
Q

Compare the solubility of polar substances in ether and alcohol and the reason for this

A

Polar substances are nearly soluble in ether as they are in alcohols

Due to ethers having a large dipole moments as well as the ability to serve as hydrogen bond receptors

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11
Q

The non bonding pairs effectively ________ cations

A

Solvate

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12
Q

Why are small anions not as soluble in ethers even nearly as much as they are in alcohols?

A

Ethers are not hydrogen-bond donors so do not solvate small anions well like alcohols

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13
Q

How do cations solvate in ethers?

A

Cations is strongly solvate strongly in ethers due to being solvated by the ethers lone pair of electrons

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14
Q

Evaluate how soluble are ions are in ethers

A

Ions are moderately soluble in ethers as cations are strongly soluble but anions do not solvate well

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15
Q

For what reagents can alcohols not be used to solvate?

A

Alcohols cannot be used as solvents for reagents that are more strongly basic than the alkoxide ion

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16
Q

Why can alcohols not be used as solvents for reagents that are more basic than the alkoxide ion?

A

This is because the hydroxyl group quickly protonates the base, destroying the basic reagent

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17
Q

What ethers are commonly used for solvents for organic reactions?

A

THF, Dioxane and DME

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18
Q

Why can ethers be used as solvents for very strong polar bases?

A

Ethers are nonhydroxylic and are normally unreactive towards strong bases like Grignard reagents that require polar solvents

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19
Q

What are Criwn Ether complexes?

A

These are cyclic polyethers that specifically solvate metal cations by complexing the metal in the center of the ring

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20
Q

Different crown ethers solvate different cations depending on…

A

Depending on the relative sizes of the crown ether, the cation and the number of bijding sites of the cation

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21
Q

Complication by crown ethers often allow polar inorganic salts to…

A

Dissolve in no polar organic solvents

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22
Q

Generally cyclic ethers behave like ______ ______. This is because…

A

Cyclic ethers

The chemistry of the ether functional group is the same whether it is an open chain or a ring

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23
Q

Cyclic ethers are examples of….

A

Heterocyclic compounds containing a ring, in which a ring atom is not carbon

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24
Q

What are epoxies?

A

Epoxides are 3 membered ring ethers, they make up one of the cyclic ethers that behave differently than open chain ethers

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25
Q

Compare the reactivity of epoxides with ethers and give a reason

A

Epoxides are more reactive than ethers due to the strain of having a 3 membered ring

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26
Q

How are epoxides named?

A

Formed by adding oxide to the name of the equivalent alkene.

E.g. 2 carbon epoxides ring- ethylene oxide

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27
Q

What peroxy acid is commonly used to synthesize ethers?

A

Meta-chloroperoxybenzoic acid(MCPBA)

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28
Q

Explain the synthesis of epoxides

A

An alkene is reacted with peroxy acid to form an epoxides and a carboxylic acid. (An oxygen is donated from a peroxyacid to an alkene)

This reaction is done in the presence of an aprotic acid

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29
Q

Why is an aprotic acid used in the synthesis of epoxides?

A

An aprotic acid is used to prevent the opening the epoxides

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30
Q

State 2 ways epoxides can be converted to alcohols

A
  1. Reaction of epoxides with LiAlH4 and H2O to form the alcohol
  2. Reaction if epoxides with Grignard and organolithium reagents
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31
Q

Explain the reaction of epoxides with Grignard and orhanilithium reactions

A

Grignard and organolithium reagents attack epoxides to give ring-opened alcohols after protonation

Attack occurs on less substituted carbon of the ring

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32
Q

Explain the reaction of epoxides with lithium aluminum hydride and water

A

Epoxides are reduced to alcohols when treated with lithium aluminum hydride

The hydride is transferred to the less substituted cargo

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33
Q

What are oxetanes?

A

4 membered cyclic ethers

34
Q

Compare the reactivity of epoxides, ethers and oxetanes

A

Because the 4 membered ring causing strain which makes them more reactive than ethers but still less reactive than epoxides

35
Q

What is a furan?

A

A five membered cyclic ether, which are commonly named after an aromatic member of this group, furan

36
Q

Tetrahydrofuran (THF) …

A

Is a saturated five membered ring, is one of the most polar ethers

37
Q

What is a use for tetrahydrofuran(THF)?

A

An excellent nonhyydroxilic organic solvent for polar reagents

38
Q

Shaft are pyrans?

A

Pyrans/oxanes are six membered cyclic ethers

They are commonly name as derivatives of pyran- an unsaturated pyran e.g.

4-methylpyran

39
Q

How do dioxanes effect DNA?

A

They associate with DNA and cause a misreading of the genetic cause

40
Q

Why are most dioxanes dangerous?

A

Most dioxanes are toxic and carcinogenic

41
Q

What are dioxanes?

A

Heterocyclic ethers with two oxygen atoms in a sex membered ring

42
Q

What is the mist common dioxane?

A

Dioxane with two oxygens with 1,4-relationship

43
Q

List the ways in which ethers can be synthesized

A
  1. Williamson method
  2. Alkoxymercuration-demercuration reaction/ addition of alcohol across a double bond
  3. Bimolecular condensation of alcohols: industrial synthesis
44
Q

What mechanism does Williamson ether use?

A

Sn2 attack

45
Q

Explain the reasoning of how a Williamson ether synthesis works

A
  • First a strong base is added to deprotonate the alcohol, the alkoxide ion produced then attacks an alkyl halide
  • Secondary alkyl halides and tosylate are occasionally used, but elimination competes and the yield is often poor
46
Q

How to perform a Williamson ether synthesis?

A

Strong base is added to alcohol and the resulting alkoxide ion reacts with an unhindered primary alkyl halide or tosylate

47
Q

Why is an ether more volatile than an alcohol with comparable molecular formula?

A

Inter molecular hydrogen bonding in alcohols

48
Q

Ethers May be used as solvents because they react only with one of the following reactants?

Acids
Bases
Oxidising agents
Reducing agents

A

Acids

49
Q

The boiling point of ethyl alcohol is much higher than that of dimethyl ether though both have the same molecular weight. Why?

A

Ethyl alcohol shows hydrogen bonding

50
Q

The Williamson ether synthesis produces ethers by reacting which of the following?

A

Alkoxide and aldehyde

51
Q

The reaction given below is known as by which of the following reaction?

C2H5ONa + IC2H5 -> C2H5OC2H5+ NaI

A

Williamson synthesis

52
Q

What will be the reactant and the reaction condition for the given reaction?

CH3CH2OH +? -> C2H5OC2H5

A

H2SO4, 413K

53
Q

Name 3 ways ethers can be synthesized

A
  • Williamson method
  • Addition of alcohol across a double bond: Alkoxymercuration-demercuration reaction
  • Bimolecular condensation of alcohols: Industrial synthesis
54
Q

What is industrial ether synthesis used to make?

A

Used to make symmetrical ethers from primary alcohols

55
Q

Review bimolecular condensation as a method for making unsymmetrical ethers

A

A poor method for making unsymmetrical ethers(like ethyl methyl ether) due to being a random process producing different combinations of both alcohols that will be difficult to separate

56
Q

What happens when temperature is too high in industrial synthesis in ether?

A

Alkene forms

57
Q

What conditions are needed in industrial synthesis of ether?

A

Sulfric acid( H2SO4)

140 degrees Celsius

58
Q

Evaluate the bimolecular condensation of ether as a lab and an industrial method

A

Industrial method- a good method

Lab synthesis- not good

59
Q

How can ethers be cleaved and what are they cleaved?

A

Can be cleaved with HBr or HI to give alkyl bromides or alkyl iodine’s

60
Q

How can ethers be converted to to alkyl bromides or alkyl iodide?

A

Cleaved with heating with HBr or HI and forms water

61
Q

Hydrogen halides are most and least reactive

A

Hydrogen iodide- most reactive

Hydrogen fluoride - is not reactive

62
Q

What happens in phenyl ether cleavage with hydrogen halides?

A

Phenyl ether converted to phenol by hydrogen bromide / iodide and alkyl bromide/iodide

63
Q

Why can phenol not react further with HI or HBr to ecome a hydrogen halide?

A

SN2 reaction cannot occur on a sp2 carbon

64
Q

What happens when ethers are stored in the presence of atmospheric oxygen ?

A

They slowly oxidize to produce hydroperoxides and dialkyl peroxides

65
Q

Why are hydroperoxides and dialkyl peroxides dangerous?

A

These are explosive

66
Q

What is autoxidation?

A

The spontaneous oxidation by atmospheric oxygen

67
Q

What are sulfides(thioethers)?

A

R—S—R’

68
Q

How are sulfides prepared?

A

Sulfides are prepared by treating a primary or secondary alkyl halide with a thiolate ion (RS) which is the sulfur analog of an alkoxide ion

69
Q

Describe the reaction mechanism to synthesize a sulfide(thioether)

A

Reaction occurs by Williamson ether synthesis which is an SN2 reaction

70
Q

How are Sulfides/thioethers named?

A

Replacing the “ether” with “sulfide” in common name or “alkylthio” for “alkoxy” in IUPAC name

E.g.

methyl phenyl sulfide

Methylthiobenzene

71
Q

What are thiols?

A

They are sulfur analogues of alcohols

72
Q

How are thiols named?

A

In the same way as alcohols but with the suffix -thiol used in place of -ol

73
Q

What is the functional group of thiols?

A

The SH group, A.K.A. a Mercapto group

74
Q

How are thiolates synthesized?

A

Are synthesized by the Williamson ether synthesis reaction using dithiolate as a nucleophile and reacting with a primary alkyl halide

75
Q

What ethers and ether compounds can be synthesized by Williamson ether synthesis?

A
  • ethers
  • phenyl ethers can be produced by phenoxide ions reacting with a strong base and unhindered primarybalkyl halide
  • Thiolates when using dithiolate as the nucleophile and then reacting with a primary alkyl halide
76
Q

Describe the reaction to produce phenyl ethers using a phenol halides or tosylates

A

Phenyl halides nor tosylates can be used to synthesize phenyl ethers

77
Q

Briefly describe the alkoxymercuration-demercuration reaction

A

Adds a molecule of an alcohol across a double bond of an alkene to produce an ether

Alcohol= ROH

RO bonds to one carbon and H binds to the adjacent carbon

78
Q

What is the type of molecule formed from the first step of mercurial ether?

A

A mercurial ether

79
Q

What are the reagents of alkoxymercuration-demercuration?

A
  1. Alkene
  2. Hg(OAc)2 and R-OH(alcohol)
  3. NaBH4
80
Q

What are the reagents in the first step of alkocymercuration-demercuration?

A
  1. Alkene

2. Hg(OAc)2 and ROH

81
Q

What is another name for pyrans?

A

Oxans- six membered cyclic ethers

82
Q

How common are oxetanes?

A

Not very common

O Chem 2 (22 decks)

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