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O Chem 2 > Ethers, Epoxides And Sulfides > Flashcards

Ethers, Epoxides And Sulfides Flashcards

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
Compare the reactivity of epoxides with ethers and give a reason
Epoxides are more reactive than ethers due to the strain of having a 3 membered ring
26
How are epoxides named?
Formed by adding oxide to the name of the equivalent alkene. E.g. 2 carbon epoxides ring- ethylene oxide
27
What peroxy acid is commonly used to synthesize ethers?
Meta-chloroperoxybenzoic acid(MCPBA)
28
Explain the synthesis of epoxides
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
29
Why is an aprotic acid used in the synthesis of epoxides?
An aprotic acid is used to prevent the opening the epoxides
30
State 2 ways epoxides can be converted to alcohols
1. Reaction of epoxides with LiAlH4 and H2O to form the alcohol 2. Reaction if epoxides with Grignard and organolithium reagents
31
Explain the reaction of epoxides with Grignard and orhanilithium reactions
Grignard and organolithium reagents attack epoxides to give ring-opened alcohols after protonation Attack occurs on less substituted carbon of the ring
32
Explain the reaction of epoxides with lithium aluminum hydride and water
Epoxides are reduced to alcohols when treated with lithium aluminum hydride The hydride is transferred to the less substituted cargo
33
What are oxetanes?
4 membered cyclic ethers
34
Compare the reactivity of epoxides, ethers and oxetanes
Because the 4 membered ring causing strain which makes them more reactive than ethers but still less reactive than epoxides
35
What is a furan?
A five membered cyclic ether, which are commonly named after an aromatic member of this group, furan
36
Tetrahydrofuran (THF) ...
Is a saturated five membered ring, is one of the most polar ethers
37
What is a use for tetrahydrofuran(THF)?
An excellent nonhyydroxilic organic solvent for polar reagents
38
Shaft are pyrans?
Pyrans/oxanes are six membered cyclic ethers They are commonly name as derivatives of pyran- an unsaturated pyran e.g. 4-methylpyran
39
How do dioxanes effect DNA?
They associate with DNA and cause a misreading of the genetic cause
40
Why are most dioxanes dangerous?
Most dioxanes are toxic and carcinogenic
41
What are dioxanes?
Heterocyclic ethers with two oxygen atoms in a sex membered ring
42
What is the mist common dioxane?
Dioxane with two oxygens with 1,4-relationship
43
List the ways in which ethers can be synthesized
1. Williamson method 2. Alkoxymercuration-demercuration reaction/ addition of alcohol across a double bond 3. Bimolecular condensation of alcohols: industrial synthesis
44
What mechanism does Williamson ether use?
Sn2 attack
45
Explain the reasoning of how a Williamson ether synthesis works
- 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
How to perform a Williamson ether synthesis?
Strong base is added to alcohol and the resulting alkoxide ion reacts with an unhindered primary alkyl halide or tosylate
47
Why is an ether more volatile than an alcohol with comparable molecular formula?
Inter molecular hydrogen bonding in alcohols
48
Ethers May be used as solvents because they react only with one of the following reactants? Acids Bases Oxidising agents Reducing agents
Acids
49
The boiling point of ethyl alcohol is much higher than that of dimethyl ether though both have the same molecular weight. Why?
Ethyl alcohol shows hydrogen bonding
50
The Williamson ether synthesis produces ethers by reacting which of the following?
Alkoxide and aldehyde
51
The reaction given below is known as by which of the following reaction? C2H5ONa + IC2H5 -> C2H5OC2H5+ NaI
Williamson synthesis
52
What will be the reactant and the reaction condition for the given reaction? CH3CH2OH +? -> C2H5OC2H5
H2SO4, 413K
53
Name 3 ways ethers can be synthesized
- Williamson method - Addition of alcohol across a double bond: Alkoxymercuration-demercuration reaction - Bimolecular condensation of alcohols: Industrial synthesis
54
What is industrial ether synthesis used to make?
Used to make symmetrical ethers from primary alcohols
55
Review bimolecular condensation as a method for making unsymmetrical ethers
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
What happens when temperature is too high in industrial synthesis in ether?
Alkene forms
57
What conditions are needed in industrial synthesis of ether?
Sulfric acid( H2SO4) 140 degrees Celsius
58
Evaluate the bimolecular condensation of ether as a lab and an industrial method
Industrial method- a good method Lab synthesis- not good
59
How can ethers be cleaved and what are they cleaved?
Can be cleaved with HBr or HI to give alkyl bromides or alkyl iodine’s
60
How can ethers be converted to to alkyl bromides or alkyl iodide?
Cleaved with heating with HBr or HI and forms water
61
Hydrogen halides are most and least reactive
Hydrogen iodide- most reactive Hydrogen fluoride - is not reactive
62
What happens in phenyl ether cleavage with hydrogen halides?
Phenyl ether converted to phenol by hydrogen bromide / iodide and alkyl bromide/iodide
63
Why can phenol not react further with HI or HBr to ecome a hydrogen halide?
SN2 reaction cannot occur on a sp2 carbon
64
What happens when ethers are stored in the presence of atmospheric oxygen ?
They slowly oxidize to produce hydroperoxides and dialkyl peroxides
65
Why are hydroperoxides and dialkyl peroxides dangerous?
These are explosive
66
What is autoxidation?
The spontaneous oxidation by atmospheric oxygen
67
What are sulfides(thioethers)?
R—S—R’
68
How are sulfides prepared?
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
Describe the reaction mechanism to synthesize a sulfide(thioether)
Reaction occurs by Williamson ether synthesis which is an SN2 reaction
70
How are Sulfides/thioethers named?
Replacing the “ether” with “sulfide” in common name or “alkylthio” for “alkoxy” in IUPAC name E.g. methyl phenyl sulfide Methylthiobenzene
71
What are thiols?
They are sulfur analogues of alcohols
72
How are thiols named?
In the same way as alcohols but with the suffix -thiol used in place of -ol
73
What is the functional group of thiols?
The SH group, A.K.A. a Mercapto group
74
How are thiolates synthesized?
Are synthesized by the Williamson ether synthesis reaction using dithiolate as a nucleophile and reacting with a primary alkyl halide
75
What ethers and ether compounds can be synthesized by Williamson ether synthesis?
- 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
Describe the reaction to produce phenyl ethers using a phenol halides or tosylates
Phenyl halides nor tosylates can be used to synthesize phenyl ethers
77
Briefly describe the alkoxymercuration-demercuration reaction
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
What is the type of molecule formed from the first step of mercurial ether?
A mercurial ether
79
What are the reagents of alkoxymercuration-demercuration?
1. Alkene 2. Hg(OAc)2 and R-OH(alcohol) 3. NaBH4
80
What are the reagents in the first step of alkocymercuration-demercuration?
1. Alkene | 2. Hg(OAc)2 and ROH
81
What is another name for pyrans?
Oxans- six membered cyclic ethers
82
How common are oxetanes?
Not very common

O Chem 2 (22 decks)

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