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Organic Chemistry > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

What is the functional group of alcohols?

What is this called?

A

-OH

The hydroxyl group

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2
Q

What is the general formula for alcohols ?

A

Cn H2n+1 OH

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3
Q

How do you classify an alcohol?

A

By the number of carbons attached to the carbon carrying the OH

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4
Q

What is the equation for the fermentation of glucose?

A

(Yeast)

C6H12O6 ———-> 2ethanol +2CO2

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5
Q

Give the conditions of the fermentation of ethanol

A 
Yeast provides enzymes as a catalyst 
35 degrees C so enzymes don’t denature 
Anaerobic respiration (oxygen free atmosphere)
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6
Q

What is the yield of ethanol from fermentation?

A

15%

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7
Q

What process is used to separate ethanol from the reaction mixture?

A

Fractional distillation

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8
Q

What are the conditions for the direct hydration of ethene?

A

Steam and concentrated H2SO4 or H3PO4

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9
Q

Give the details of a fermentation reaction

A

Rate: slow
Quality of product: impure
Raw material: sugar (renewable)
Type of process: batch

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10
Q

Give details on the hydration of ethene

A

Rate: slow
Quality: pure
Raw material: ethene from oil (finite)
Process: Continuous

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11
Q

Compare batch vs continuous processes

A

Batch: cheap equipment but expensive on manpower

Continuous: cheap on manpower, expensive equipment

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12
Q

What is a biofuel?

A

A fuel produced from renewable biological resources

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13
Q

Define carbon neutral

A

An activity that has no net annual carbon emissions to the atmosphere

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14
Q

Why is fermentation considered carbon neutral?

A

Photosynthesis absorbs 6 moles of CO2

Fermentation releases 6 moles of CO2

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15
Q

Is fermentation actually carbon neutral?

A

No: CO2 is produced in other processes involved eg transport and harvest

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16
Q

Is ethanol a biofuel?

A

Yes it is used as motor fuel when mixed with petrol

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17
Q

Mechanism for an alcohol to an alkene

Conditions??

A

Elimination

Heated with concentrated H2SO4

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18
Q

What is the name of the reaction turning an alcohol to an alkene?

A

Dehydration

Water is eliminated

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19
Q

What are the stages of an elimination reaction?

A

The alcohol oxygen’s lone pair is donated to a H+ provided by acid catalyst

Oxygen gains H+ and a positive charge

A hydrogen is lost from an adjacent carbon and the e- in the C-H bond move into the positively charged oxygen

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20
Q

What are the stages of separation for an impure organic liquid eg cyclohexene

A

Place impure organic liquid into a separating funnel and add a small amount (10cm3) of sodium hydrogen carbonate solution to eliminate XS acid catalyst

Stopper separating funnel and shake

Periodically invert and open tap to release pressure

Allow funnel to stand and layers to separate

Remove stopped and run off top and bottom layers into separate beakers

Discard aqueous layer

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21
Q

Why must you periodically open the tap of the separating funnel?

A

To release a build up of pressure coming from the acid catalyst reaction with the sodium hydrogen carbonate, creating CO2

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22
Q

Once you have separated the organic liquid, there may be a little water left. What do you do now???

A

Add a spatula of drying agent (eg Calcium Chloride or MgSO4) to organic liquid

Swirl and add drying agent until the liquid changes from cloudy to clear

Filter to remove drying agent

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23
Q

List the equipment for distillation reaction

A

Round bottom flask
Thermometer
Condenser
Heat

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24
Q

What is the distillate?

A

The product that evaporated and is condensed

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25
Q

Describe the method for distillation

A

Place mixture in round bottom flask attached to side arm with condenser, with a few anti-bumbing granules and heat

As product is formed it will evaporate, travel up the neck and down the condenser, where it will cool and drip into the collection vessel

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26
Q

How do we prevent the evaporation of the distillate?

A

Cool the distillate by placing the collection vessel in an ice bath

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27
Q

What is used to oxidise alcohols?

How is this presented in equations?

A

Acidified potassium dichromate

[O]

28
Q

What is observed when an alcohol is oxidised?

A

Colour change from orange to green

29
Q

What does the oxidation of a primary alcohol produce?

What if this is further oxidised?

A

Aldehyde

Carboxylic acid

30
Q

What does the oxidation of a secondary alcohol produce?

A

Ketone

31
Q

What does the oxidation of a tertiary alcohol produce?

A

Nothing

32
Q

Order alcohol, aldehyde, and carboxylic acid in order of boiling point (highest to lowest)

Explain

A

Carboxylic acid > alcohol > aldehyde

Carboxylic acid: has hydrogen bonds and is bigger than alcohol so there are more VdW forces

Alcohol: has hydrogen bonds

Aldehyde: it’s permanent dipole-dipole forces are weaker than hydrogen bonds

33
Q

Describe distillation to form an aldehyde (or ketone)!

A

Primary alcohol and potassium dichromate are dripped intk a WARM solution of H2SO4 (to make acidified potassium dichromate)

Aldehyde forked is immediately distilled off to prevent further oxidation

The boiling point of aldehyde is lower than that of an alcohol or carboxylic acid.

34
Q

How do you produce a carboxylic acid?

A

Oxidise a primary alcohol under reflux

35
Q

Why use reflux?

A

The vapour produced condensed and drips back into the reaction flask which prevents it escaping and will oxidise to form a carboxylic acid

36
Q

What do

a) secondary
b) tertiary

Alcohols oxidise to?

A

a) ketones

b) not easily oxidised

37
Q

Explain the colour changes during oxidation reactions

A

When potassium dichromate (orange) reacts with primary or secondary alcohols it is reduced to green chromium ions

38
Q

How can oxidation reactions be used to distinguish between primary, secondary and tertiary alcohols?

A

Primary and secondary will go from orange to green with potassium dichromate

Tertiary will not

39
Q

Give the general formula for aldehydes

How is it different to that of ketones?

A

Cn H2n O

It is the same

40
Q

How are aldehydes different to ketones

A

Ketones have the C=O bond in the middle of the C chain

Aldehydes have the C=O on the end

41
Q

What suffix is used for

a) aldehydes
b) ketones?

A

a) -al

b) -one

42
Q

When do you use number in the name of an aldehyde?

A

NEVER

43
Q

When can ketones be oxidised?

How and why is this avoided?

A

When reacted with a powerful oxidising agent causing C-C bonds to break and form a mixture of carboxylic acids

A milder oxidising agent must be used, which can oxidise an aldehyde but not a ketone

44
Q

What two mild oxidising agents can oxidise an aldehyde but not a ketone?

A

Tollen’s Reagent

Fehling’s solution

45
Q

a) When added to an aldehyde, what happens to Tollen’s reagent?
b) What about for a ketone?

A

a) Aldehyde oxidised to carboxylic acid
Silver ions reduced to silver
This produces a silver mirror

b)No observable change

46
Q

Give the ionic equation when
a) Tollen’s Reagent

b) Fehling’s Solution

is added to an aldehyde

A

a) Ag+ + e- —-> Ag

b) Cu2+ + e- —-> Cu+

47
Q

What is the colour change for aldehyde + Fehling’s Solution?

A

Forms a brick red PPT

48
Q

Test for alkene

A

Shake with Bromine water (orange to colourless)

49
Q

Test for carboxylic acid

A

Add sodium carbonate (effervescence)

50
Q

Are C=O bonds polar?

What does this mean for nucleophiles?

A

Yes

It is readily attacked by nucleophiles

51
Q

Name the mechanism for the reduction of an aldehyde/ ketone to an alcohol

A

Nucleophilic addition

52
Q

What is used as a reducing agent to turn an aldehyde to an alcohol?

What does this provide?

A

NaBH4

H- ions

53
Q

Name the reaction for nucleophilic addition

A

Reduction

54
Q

Describe the mechanism for nucleophilic addition

A

Lone pair on H- goes to C of C=O bond, leaving O with a single bond and negative charge

Lone pair on O- goes to H+, forming an OH group

55
Q

Mechanism for ketone/ aldehyde to hydroxynitriles

Conditions

A

Nucleophilic addition

KCN and DILUTE HCL

56
Q

How do you name hydroxynitriles?

A

Use a hydroxy- prefix and -nitrile suffix

The nitrile carbon is always number one in the chain

57
Q

Describe the nucleophilic addition to form hydroxynitriles

A

Lone pair on CN- goes to C of C=O bond, leaving O as negative with a single bond

Lone pair on O- goes to H+ from HCl

58
Q

Nucleophilic addition forms optical isomers. What ratio are they in and what is this called?

A

Equal

A racemic mixture

59
Q

Why are racemic mixtures optically inactive?

A

Equal amounts of enantiomers rotate a plane of polarised light in opposite directions equally and cancel each other.
Therefore polarised light is not rotated

60
Q

For nucleophilic addition, why is a racemic mixture formed?

A

The carbonyl group is planar

There is an equal chance of the nucleophile attack from either side (above or below)

61
Q

What is an anime functional group?

A

-CH2NH2

62
Q

How can a nitrile functional group be turned into an anime functional group?

What kind of reaction is this?

A

Catalytic hydrogenation

Reduction

63
Q

What is needed for the catalytic hydrogenation of nitriles?

A

Hydrogen

Nickel catalyst

64
Q

Are nitrile or amines more reactive?

A

Amines

65
Q

Mechanism for alkyl hydrogen sulphate -> alcohol

A

Hydrolysis

Warm
H2O

66
Q

Alkene to alcohol

A

Electrophilic addition / hydration

H2O
Conc H2SO4

67
Q

What kinda of IMF do aldehydes have

A

Dipole dipole

Organic Chemistry (12 decks)

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