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Chem 281 > Chapter 11 Ethers and Alcohols > Flashcards

Chapter 11 Ethers and Alcohols Flashcards

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1
Q

What is the boiling point of an ether comparable to?

A

Hydrocarbons with the same number of carbons

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2
Q

What has a higher boiling point ethers or alcohols and why?

A

Alcohols because they have hydrogen bonds

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3
Q

What are the relative solubilities of hydrocarbons, ethers, and alcohols in water?

A

Ethers and alcohols have high solubility relative to hydrocarbons because they can hydrogen bond with water

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4
Q

What happens to the relative solubility of alcohols in water and why?

A

As alcohols get longer hydrocarbon chains they become more alkane like and therefore their solubility decreases

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5
Q

What is a way to make alcohols from alkenes?

List the steps and reagents

A

Acid-catalyzed Hydration of Alkenes

  1. (Acid/Water) The double bond takes the Hydrogen from the acid and becomes a carbocation with one H and one positive carbon
  2. (Water in eq) Water attacks the carbocation and bonds
  3. (Water in eq) Another water molecule deprotonates the H2O+
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6
Q

What are some alcohols that are infinitely soluble in water?

A

Methanol, Ethanol etc.

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7
Q

What are some features of acid-catalyzed hydration of alkenes into alcohols?

A
  1. Markovnikov Regioselective ie. Adds to most substituted carbon
  2. Possible carbocation rearrangement
  3. Syn addition (To same side)
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8
Q

What is a way to make alcohols from alkenes?

List the steps and reagents

A

Oxymercuration-Demercuration

  1. (Hg(OAc)2/H20, THF) OH is added to one carbon and Hg(OAc) is added to the other carbon (Anti addition)
  2. (NaBH4 or Strong base/ NaOH) This removes the Hg(OAc) and adds a Hydrogen where it ones
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9
Q

What are the 3 ways to make alcohols from alkenes and what selectivity are they?

A
  1. Acid-catalyzed hydration- Markovnikov
  2. Oxymercuration-demercuration-Markovnikov
  3. Hydroboration-Oxidation-Anti Markovinikov
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10
Q

What are some features of Oxymercuration-demercuration?

A
  1. Markovnikov Regioselective ie. Adds OH to most substituted carbon
  2. Anti Stereoselective ie. Added to carbons on opposite sides
  3. No possibility of carbocation rearrangement
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11
Q

What is a way to make alcohols from alkenes?

List the steps and reagents

A

Hydroboration-Oxidation

  1. (BH3, THF) H and BH2 are added to adjacent carbons
  2. (NaOH,H2O2) OH- attacks and knocks off the BH2 molecule
    via. SN2
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12
Q

What are the features of Hydroboration-Oxidation

A
  1. Antimarkovnikov regioselective
  2. Syn stereoselective
  3. No possibility of carbocation rearrangement
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13
Q

What type of mechanism should you NOT use to create an alcohol from an alkene when there is a T-butyl of isopropyl group and why?

A

Don’t use acid-catalyzed hydration because it will rearrange

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14
Q

What are the 3 main points to remember when reacting alcohols?

A
  1. Reactions happen because the -OH group is nucleophilic and weakly basic
  2. The H atom of the -OH is weakly acidic
  3. -OH group can be converted to a good leaving group
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15
Q

What is a good way to turn an -OH group into a good LG?

A

Pronate it with a strong acid

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16
Q

What should any nucleophile in acidic solution be?

A

A weak base

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17
Q

What do alcohols have acidities similar to?

A

Water

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18
Q

Rank the acidities and basicities of:

NH3
Terminal alkyne
H20
ROH
H2
RH
A

Most Acidic to least:

H20
ROH
Terminal alkyne
H2
NH3
RH

Most Basic to least:

R-
NH2-
H-
Deprotonated terminal alkyne
RO-
OH-
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19
Q

What was the general trend of the last slide?

A

H2O and ROH (alcohol) were stronger acids and weaker bases

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20
Q

What are 3 ways to convert alcohols to alkyl halides?

A
  1. H-X (Hydrogen halide)
  2. PBR3
  3. SOCL2
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21
Q

What might be a purpose of changing an alcohol to an alkyl halide?

A

We might do this to protect the alcohol if it is in acidic solution because otherwise, it will H-bond

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22
Q

What is the reactivity of alcohols ranked?

What is the order of reactivity of hydrogen halides?

A

Alcohols: 3>2>1>Meth

Hydrogen Halides: HI>HBr>HCl HF doesn’t react

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23
Q

Will and Alcohol react with Na-X, why or why not?

What can you do to change this?

A

No, because the OH- is a bad leaving group

We can acid catalyze it to turn the OH into a good leaving group

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24
Q

What conditions are used to turn an alcohol into an alkyl halide and why?

A

Acidic, need to make the OH- into a good leaving group

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25
Q

How do meth and 1 alcohols to form alkyl halides?

List steps reactants and conditions

A

These reactions occur in Acid when it is not H-X

Meth/1- (Use Na or H with a halide AND the alcohol) SN2

Step 1. The Halogen splits and turns into a halide either by pronating the OH or losing the Na in which case it must be acid catalyzed

Step 2. If needed the acid pronates the OH group

Step 3. The halide attacks via SN2 and backside attacks knocking off the OH LG

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26
Q

How do 2,3, benzylic, and allylic alcohols to form alkyl halides?
List steps reactants and conditions

A

These reactions occur in Acid when it is not H-X

2,3, Benzylic, allylic (Halide and Alcohol) SN1

A carbocation intermediate is formed in this reaction

Step 1. The OH group is pronated-(Fast)

Step 2. The OH group leaves-(Slow)

Step 3. The halide attacks (Fast)

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27
Q

What do we make when we react PBr3 with 3 counts of alcohol?

A

Alkyl halides and H3PO3

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28
Q

What are the steps in PBr3 reacting with an alcohol? and what do we need?

A

We need PBr3 and 1 or 2 alcohol

Step 1: O attacks the electropositive Phosphorous knocking off a Br

Step 2: The Br- attacks and knocks off the +HOPBr2

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29
Q

What are characteristics of PBr3 reacting with alcohol?

A
  1. Happens with 1 and 2 alcohols
  2. No carbocation rearrangement, especially if below 0 degrees Celsius
  3. Adds a bromine
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30
Q

What are the steps in the reaction of SOCL2 and alcohol? and what do we need?

A

We need SOCl2, Pyridine, and a 1 or 2 alcohol

Don’t need to know mechanism, also we use pyridine to pick up extra Hydrogens

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31
Q

What are characteristics of SOCl2 reacting with alcohol

A
  1. 1 or 2 alcohol
  2. No carbocation rearrangement especially if below 0 degrees Celsius
  3. Use pyridine as a Hydrogen grabber
  4. Adds a chlorine
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32
Q

What are 3 good Leaving groups?

A
  1. Tosylate
  2. Mesylate
  3. Trifates
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33
Q

What is a problem with reacting a primary alcohol via SN2?

A

OH is a bad leaving group so we can convert it to a good one

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34
Q

What is the reaction to convert a primary alcohol into a good leaving group and what do we need?

A

We add Tosyl, mesyl, or trifyl chloride and use pyridine as a reactant to add these to make OTs, OMs, or OTf.

This will allow a nucleophile to attack via SN2

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35
Q

What happens to stereochemistry when we convert OH to a good LG with Ms, Ts etc.

A

Stereochem is retained, but when the nucleophile come in via SN2 and inverts the stereochemistry

36
Q

How do you show the inversion of stereochemistry at a given carbon at on a ring system?

A

Switch at the same carbon from the axial or equatorial to the corresponding axial or equatorial

37
Q

What are the ways to make ethers?

A
  1. Intermolecular dehydration of alcohols-Alcohol and Acid
  2. Williamson ether synthesis-Alcohol and Base
  3. Alkoxy-Demercuration-Alkyne with mercury, alcohol, and base
38
Q

Explain the steps and what is needed for dehydration of an alcohol to make an ether?

What is this synthesis good for making?

A

We need an alcohol, an acid, the exact alcohol as before, and heat

Step 1. The acid pronates the alcohol

Step 2. The alcohol attacks and the water leaves

Step 3. Water removes the H from the pronated ether

ONLY GOOD FOR SYMMETRICAL ETHERS

39
Q

How do we make 3 different ethers with one reaction?

A

React 2 different primary alcohols with acid. This gives you a combination of all 3 R-O-R’, R-O-R, R’-O-R’

40
Q

What is a good way to make an ether with an ether connected to 1 carbon on one side and 3 carbons on the other side?

What are the steps?

A

Add a primary and tertiary alcohol in catalytic acid (H2SO4)

Step 1: The acid makes the 3 alcohol into a good LG and a carbocation forms

Step 2: The primary ether attacks and joins

41
Q

What are some characteristics reactants of the Williamson ether synthesis?

A
  1. It occurs via SN2 so the nucleophile (R-X) must be primary
  2. The substrate is R’OH
  3. R’OH can be 1, 2, or 3
42
Q

What are the steps of the Williamson ether synthesis? and what is needed

A

A primary Alkyl halide, a 1,2,or3 alcohol, and A BASE

Step 1. The base removes the H from the alcohol

Step 2. The alkoxide attacks the primary alkyl halide via SN2

43
Q

What bond must break in retrosynthesis of Williamson ether?

A

Break the bond that gives us a primary or methyl group for the R-X

44
Q

What can happen when there are an alcohol and halide on opposite ends of a chain?

A

If it reacts with a base the alkoxide end will attach and knock of the halide creating a ring

45
Q

What happens when you react a ring with adjacent halide and OH group with a strong base if they are trans and cis?

Why does this happen?

A

Trans-An epoxide forms

Cis-No reaction occurs

46
Q

What is an easy way to form an epoxide?

A

Use cyclohexane with adjacent trans halide and OH- then react with strong base

47
Q

What do ethers do to the solubility of a molecule in water?

A

Adding an ether makes a molecule more soluble in water

48
Q

What are the steps of alkoxy-demercuration?

What is needed?

A

An alkene, (Mercury and alcohol), (Strongbase/NaOH)

Step 1: Hg(OCCF3)2 and R’OH add via Markovnikov

Step 2: The base removes the Hg group

49
Q

What are the characteristics of alkoxy-demercuration?

A
  1. Markovnikov regioselective ie.OR gets added to ore substituted
  2. The is no possibility of a rearrangement
50
Q

What are 2 kinds of protecting groups that must often be added to form ethers?

A
  1. Tert-Butyl protecting group

2. Silyl protecting group

51
Q

Why are protecting groups used?

A

To protect a hydroxyl group

52
Q

What reactants do you need to add a t-butyl group to an alcohol to form a protecting group?

A

A primary alcohol, and (Acid/2-methyl-prop-1-en)

53
Q

What can be used to remove a t-butyl group?

A

Dilute aqueous acid (H+/H2O)

54
Q

What is a Grignard reagent?

A

R-Mg-X

55
Q

Why must a primary alcohol be protected when a Grignard reagent is being used?

A

Because the MGX is positive and the double bond is negative meaning it will react with the alcohol otherwise

56
Q

What does BrMg of Grignard reagents do?

A

It leaves and creates a - charged R group

57
Q

What is a silyl ether protecting group?

A

It is a useful protecting group for primary alcohols

58
Q

How do we add a silyl ether protecting group and what do we need?

A

We need TBSCL and a primary alcohol, we react these with (imidazole/aprotic solvent)

59
Q

How do we remove a silyl protecting group?

A

Bu4NF/THF or HF (aq)/THF

60
Q

What are the steps with a protecting group?

A
  1. Add the group
  2. Add the reagent
  3. Remove the group
61
Q

What is the only thing dialkyl ethers react with and what does this do to the ether?

A

They only react with acids which pronate the O and creates a salt

62
Q

How do you cleave ethers?

A

Heat dialkyl ethers with strong acid which breaks the C-O bonds and gives us water

63
Q

What would ether cleavage of diethyl ether reacting with 2H-Br lead to?

A

H20 and 2 Bromoethane

64
Q

What are the steps of ether cleavage and what is needed?

A

Use 2 counts of acid and the ether

Step 1. The ether takes an H off the acid

Step 2. The X of the acid attacks one side of the alkyl group and the oxygen takes up the nearest bond

Step 3. Oxygen removes another proton from the acid

Step 4. The X of the acid attacks the remaining alkyl group and the O is protonated while the bond breaks

65
Q

What is an epoxide?

A

A 3 membered ring with a central oxygen

66
Q

What are the ways to make epoxides?

A
  1. Electrophilic Epoxidation-React an alkene with a peroxy acid aka peracid
67
Q

What do you need for electrophilic epoxidation?

A

An alkene and a (peracid/acid)

68
Q

What are common types of peracids and what is the structure of a peracid?

A

They are carboxylic acids with an extra O between the C and the OH

  1. MCPBA
  2. Peracetic acid
69
Q

What are the reactants and products of electrophilic epoxidation

A

Alkene + Peracid —————> Epoxide + Carboxylic Acid

70
Q

What stereochemistry happens during electrophilic epoxidation?

A

The stereochemistry is retained meaning if it is a trans of cis double bond the carbons will stay like that

It is syn (cis) addition

71
Q

What bond will form an epoxide if there are 2 double bonds?

A

The more electron dense ie. more substituted because alkyl groups push electron density into the double bond

72
Q

What about epoxides structure make them reactive compared to other ethers?

A

The highly strained ring means they are more reactive towards nucleophilic substitution

73
Q

What are the 2 ways to open an epoxide?

A
  1. Acid catalyzed-More substituted

2. Base catalyzed-Less substituted

74
Q

What are the steps of acid-catalyzed epoxide opening, what do you need, and what does it add?

A

An acid and an epoxide are needed

Step 1. Acid pronates epoxide

Step 2. Same water molecule that was an acid attack Carbon and the oxygen takes up a bond opening the ring

Step 3. Water removes proton from water on carbon

This adds an alcohol and the acid without an H

75
Q

What are the steps of base-catalyzed epoxide opening, what do you need, and what does it add?

A

A base and an epoxide are needed

Step 1. A base R-O- attacks one carbon and opens the ring

Step 2. The negative oxygen grabs a hydrogen off the base

This adds an alcohol and the base without an H

76
Q

What is a diol?

A

2 OH groups in a compound

77
Q

If an epoxide is unsymmetrical what does a base and an acid attack respectively?

A

Base-Goes to less substituted (Antimarkovnikov)

Acid-Goes to more substituted (Markovnikov)

78
Q

What happens if you add an acid to a protonated epoxide (ie. + on the O)

A

You get a R-O-H and the O is positive

79
Q

What is anti-dihydroxylation, and what is needed?

A

It is a 2 step procedure where 2 OH groups are added to create a diol via the ring opening of epoxides. An alkene ring, MCBPA and (acid/water) are needed

80
Q

What are the steps in Anti-Dihydroxylation?

A

Step 1. MCBPA creates an epoxide from the double bond

Step 2. Acid protonates the Oxygen

Step 3. Water joins the ring

Step 4. Water is deprotonated

2 OH groups are added anti

81
Q

How do you make cis-diols and trans-diols from a cyclohexene?

A 
Cis- 
Cold KMNO4 and OH-
or
1. OsO4 
2. NaHSO3 (Strong base)

Trans-

  1. MCPBA
  2. H+/H20
82
Q

What are 3 ways to make primary alcohols?

A
  1. OH- attacking an alkyl halide via SN2
  2. Girdans reactant: 1 Epoxide 2. Water
  3. Hydroboration of a terminal alkene
  4. (BH3/THF)
  5. (H2O2/NaOH)
83
Q

What are 3 ways to make a secondary alcohol?

A
  1. Terminal alkene (Acid/Water)
  2. Hydroboration of a middle alkene
  3. (BH3/THF)
  4. (H2O2/NaOH)
  5. Oxymercuration-demercuration of middle or side alkene
  6. Hg(OAc)2, H20
  7. NaBH4
84
Q

What are 3 ways to make a tertiary alcohol?

A
  1. Tertiary alkyl halide with acid and water
  2. 2-propene with acid and water
  3. Oxymercuration-demercuration of 2-propene
85
Q

What are 5 primary alcohol reactions?

A
  1. TSCl and pyridine=Terminal OTS
  2. Acid and heat=Termnal Alkene
  3. SoCl2=Terminal alkyl halide
  4. PBr3=Temrinal alkyl halide
    1. Base 2. R-X=Ether
86
Q

What are the 2 ways to make ethers?

A
  1. Williamson

2. Acid catalyzed with heat

87
Q

How do you cleave ethers?

A

Add acid, protonate and then attack with base

Chem 281 (2 decks)

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