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Organic Chemistry > Alcohols. > Flashcards

Alcohols. Flashcards

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1
Q

What is the starting material if you want to produce a primary alcohol?

A

An aldehyde.

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2
Q

What is the starting material if you want to produce a secondary alcohol?

A

A ketone.

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3
Q

What can be used to reduce carboxylic acids?

A

Lithium aluminium hydride.

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4
Q

What is normally used to reduce primary and secondary alcohols?

A

Lithium aluminium hydride. LiAlH4.

Sodium borohydride. NaBH4.

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5
Q

Can sodium borohydride be used to reduce carboxylic acids?

A

No.

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6
Q

If an ester is reduced to an alcohol, what kind of alcochol is formed?

A

A primary alcohol.

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7
Q

What is the reagent of choice for reducing esters?

A

LiAlH4. But NaBH4 can be used.

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8
Q

If an epoxide is reduced to an alcohol, how many carbons are added to the chain?

A

2.

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9
Q

How can a dialdehyde be reduced to a diol?

A

Dialdehyde can be reduced to a diol Using H2 in the presence of Nickel. It can be reduced by sodium borohydride and Lithium Aluminum hydride.

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10
Q

If a carboxylic acid and an alcohol react, what is produced?

A

An ester.

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11
Q

What will a primary alcohol oxidise into?

A

A carboxylic acid.

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12
Q

What reagent is needed to make a primary alcohol oxidise into an aldehyde?

A

PCC

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13
Q

What will a secondary alcohol oxidise into?

A

A ketone.

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14
Q

Can tertiary alcohols be oxidised?

A

No.

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15
Q

What is the oxidation number of chromium?

A

+6.

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16
Q

What gets oxidises alcohol in the liver?

A

NAD+.

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17
Q

Which enzyme turns ethanol to ethanal?

A

Alcohol dehydrogenase.

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18
Q

Alcohol to aldehyde is what kind of reaction?

A

Oxidation.

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19
Q

What inhibits aldehyde dehydrogenase?

A

Disulfiram.

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20
Q

Which enzyme helps turn pyruvic acid to lactic acid?

A

Lactic acid dehydrogenase.

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21
Q

What is the general formula of a thiol?

A

CnH2n+1SH.

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22
Q

If an alcohol is dehydrated, what is formed?

A

An alkene.

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23
Q

What is oxidation?

A

Gain of O, O2, or X2; loss of H2.

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24
Q

What is reduction?

A

Gain of H2 (or H-); loss of O or O2; and loss of X2.

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25
Q

Is the gain or loss of H+, H2O, HX, etc oxidation or reduction?

A

Neither.

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26
Q

What is the best oxidation reagent for turning a secondary alcohol into a ketone?

A

Na2Cr2O7/H2SO4.

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27
Q

What will oxidise a primary alcohol to a carboxylic acid?

A

Chromic acid/Sodium dichromate.

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28
Q

Why will chromic acid not form aldehydes?

A

Because it is too strong a reagent.

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29
Q

What can oxidise primary alcohols to aldehydes and secondary alcohols to ketones?

A

PCC. Pyridinium Chlorochromate.

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30
Q

What will the chromic acid test, test for?

A

Primary and secondary alcohols.

31
Q

Why can the chromic acid test not test for tertiary alcohols?

A

Because tertiary alcohols do not react.

32
Q

What is alcohol dehydrogenase?

A

It is a catalyst for biological oxidation reactions.

33
Q

What is the oxidising agent for biological oxidation reactions?

A

NAD+. Nicotinamide adenine dinucleotide.

34
Q

In biological oxidation, what is ethanol oxidised to?

A

Acetaldehyde, then acetic acid, which is a normal metabolite.

35
Q

In biological oxidation, what is methanol oxidised to?

A

Methanol oxidizes to formaldehyde, then formic acid, which is more toxic than methanol.

36
Q

In biological oxidation, what is ethylene glycol oxidised to?

A

Ethylene glycol oxidises to oxalic acid, which is toxic.

37
Q

What catalyses enzymatic oxidation?

A

Alcohol dehydrogenase.

38
Q

What is the oxidising agent in enzymatic oxidation?

A

NAD+.

39
Q

R-OH, is a strong or weak nucleophile?

A

Weak.

40
Q

R-O-, is a strong or weak nucleophile?

A

Strong.

41
Q

Is OH- a good leaving group?

A

No.

42
Q

What is the best way to make OH- a good leaving group?

A

By making it H2O.

43
Q

What is a tosylate ester?

A

Alcohols can be converted into a tosylate ester which is an excellent leaving group.

44
Q

What is the symbol for tosylate?

A

OTS.

45
Q

Why is the tosylate ion so stable?

A

The tosylate ion is a particularly stable anion, with its negative charge delocalised over three oxygen atoms.

46
Q

When a tosylate replaces an alcohol what is the general reaction?

A

SN2.

47
Q

What are the 2 methods of dehydrating an alcohol?

A

Dehydrate with concentrated H2SO4, then add H2.

Make a tosylate, then reduce it with LiAlH4.

48
Q

What are the limitations of H-X reactions?

A

Poor yields of alkyl chlorides from primary and secondary alcohols.

Elimination competes with substitution.

Carbocation intermediate may undergo a rearrangement.

Limited ability to make alkyl halides.

49
Q

What are characteristics of reactions with phosphorous halides?

A

Good yields with 1° and 2° alcohols.

PCl3 for alkyl chlorides (but SOCl2 better).

PBr3 for alkyl bromides.

P and I2 for alkyl iodides (PI3 not stable).

50
Q

What can thionyl chloride be used for?

A

Thionyl chloride (SOCl2) can be used to convert alcohols into the corresponding alkyl chloride in a simple reaction that produces gaseous HCl and SO2.

51
Q

What 2 reactions can vicinal diols undergo?

A

Pinacol rearrangement.

Periodic acid cleavage.

52
Q

What happens in the Pinacol rearrangement?

A

In the pinacol rearrangement, a vicinal diol converts to the ketone (pinacolone) under acidic conditions and heat.

The reaction is classified as a dehydration since a water molecule is eliminated from the starting material.

53
Q

What is the 1st step of the pinacol rearrangement?

A

The first step of the rearrangement is the protonation and loss of a water molecule to produce a carbocation.

54
Q

What is the 2nd step of the pinacol rearrangement?

A

There is a methyl shift to form a resonance-stabilized carbocation, which upon deprotonation by water, yields the pinacolone product.

55
Q

How can glycols become ketones or aldehydes?

A

Glycols can be oxidatively cleaved by periodic acid (HIO4) to form the corresponding ketones and aldehydes.

56
Q

What is the Fischer esterification?

A

Reaction of an alcohol and a carboxylic acid produces an ester.

Sulfuric acid is a catalyst.

The reaction is an equilibrium between starting materials and products, and for this reason, the Fischer esterification is seldom used to prepare esters.

57
Q

What is the best esterification reaction?

A

The esterification reaction that achieves better results by reacting the alcohol with an acyl chloride.

The reaction is exothermic and produces the corresponding ester in high yields with only HCl as a by-product.

58
Q

What is the Williamson ether synthesis?

A

Ethers can be synthesized by the reaction of alkoxide ions with primary alkyl halides in what is known as the Williamson ether synthesis.

59
Q

How does the Williamson ether synthesis happen?

A

There is an SN2 displacement reaction and as such the Williamson ether synthesis works better with primary alkyl halides to facilitate back-side attack.

60
Q

What happens is a secondary or tertiary alkyl halide is used for the Williamson ether synthesis?

A

If a secondary or tertiary alkyl halide is used, the alkoxide will act as a base and an elimination will take place.

61
Q

What are other oxidation reagents?

A

CuO, 300°C (industrial dehydrogenation).

Collins reagent.

Jones reagent.

KMnO4.

Nitric acid.

Swern oxidation.

62
Q

What is the collins reagent?

A

Cr2O3 in pyridine.

63
Q

What is the Jones reagent?

A

Chromic acid in acetone.

64
Q

Is KMnO4 and nitric acid, strong or weak oxidisers?

A

Strong.

65
Q

What is the Swern oxidation?

A

Swern oxidation: dimethylsulfoxide, with oxalyl chloride and hindered base, oxidizes 2° alcohols to ketones and 1° alcohols to aldehydes.

66
Q

What are the reagents in the Swern oxidation?

A

This reaction uses dimethyl sulfoxide (DMSO) as the oxidizing agent along with oxalyl chloride and pyridine.

67
Q

What kind of alcohols does the Swern oxidation react with?

A

Primary alcohols can be oxidised to the aldehyde.

Secondary alcohols can be oxidised to the corresponding ketone with this reaction as well.

68
Q

Why is the Swern oxidation a good reaction?

A

The by-products of this reaction can be easily separated from the products.

69
Q

How do primary, secondary and tertiary alcohols react with the Lucas reagent?

A

1° alcohols react slowly or not at all.

2° alcohols react in 1-5 minutes.

3° alcohols react in less than 1 minute.

70
Q

What happens when you react an alcohol with HCl?

A

Chloride is a weaker nucleophile than bromide.

Add ZnCl2, which bonds strongly with
 –OH, to promote the reaction.

The chloride product is insoluble.

71
Q

What is the Lucas reagent?

A

ZnCl2 in concentrated HCl.

72
Q

How do primary alcohols react with the Lucas reagent?

A

Primary alcohols react with the Lucas reagent (HCl and ZnCl2) by the SN2 mechanism.

Reaction is very slow. The reaction can take from several minutes to several days.

73
Q

How do secondary and tertiary alcohols react with the Lucas reagent?

A

Secondary and tertiary alcohols react with the Lucas reagent (HCl and ZnCl2) by the SN1 mechanism.

Organic Chemistry (9 decks)

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