Alcohols

Question 1

What is the functional group for alcohols

Answer 1

-OH
Hydroxyl group

Question 2

What is a primary alcohol

Answer 2

An alcohol with 1 alkyl group attached to the same carbon which the -OH is attached to

Question 3

What is a secondary alcohol

Answer 3

An alcohol with 2 alkyl groups attached to the same carbon which the -OH is attached to

Question 4

What is a tertiary alcohol

Answer 4

An alcohol with 3 alkyl groups attached to the same carbon which the -OH is attached to

Question 5

How can we sustainably make an alkene from an alcohol

Answer 5

Dehydrate an alcohol which is produced via the fermentation of glucose from plants in the presence of an acid catalyst

Question 6

What do we call the process of eliminating water from a molecule

Answer 6

Dehydration

Question 7

What is the benefit of dehydrating an alcohol which is produced via the fermentation of glucose from plants to produce an alkene rather than extracting them from crude oil

Answer 7

Crude oil is non-renewable therefore this process is not sustainable. Plants are renewable and so that process is sustainable

Question 8

How can we form an alcohol from an alkene

Answer 8

Hydrate the alkene in the presence of an acid catalyst

Question 9

Give an equation for the dehydration of ethanol to produce an alkene

Answer 9

Must be done in warm conditions (under reflux) and in the presence of concentrated sulfuric acid

Question 10

What is the mechanism by which the dehydration of alcohols to form an alkene occurs

Answer 10

Acid catalysed elimination

Question 11

What can alkenes which are produced by the dehydration of alcohols be used for. What is the benefit of this over an alternative method

Answer 11

Used to produce addition polymers without using monomers derived from crude oil.

Question 12

Outline the mechanism for the formation of ethene via the dehydration of ethanol

Answer 12

Elimination

Question 13

What can occur when we dehydrate secondary or tertiary alcohols to form an alkene

Answer 13

May form 2 different alkenes due to the ability for the double bond to occur on either side of the OH group

Question 14

When we dehydrate an alcohol, the mixture is impure. What are the components of this impure mixture

Answer 14

Alkene
Alcohol
Water
Acid

Question 15

How can we separate an impure mixture produced from the dehydration of an alcohol

Answer 15

Distillation

Question 16

What is distillation

Answer 16

The separation of chemicals by boiling point

Question 17

What can we do to further purify an impure mixture produced from the dehydration of an alcohol which has already been distilled

Answer 17

We can use a separation funnel to separate aqueous and organic layers
The addition of a drying agent ( to remove any H2O)

Question 18

What is the desired product from the dehydration of an alcohol

Answer 18

A pure alkene

Question 19

What are the 3 steps in producing cyclohexene from an alcohol

Answer 19

Distillation
Separation
Purification

Question 20

What alcohol is cyclohexene produced from

Answer 20

cyclohexanol

Question 21

What is the reagent and conditions required for the dehydration of an alcohol to form an alkene, and what is the name of the mechanism

Answer 21

Elimination
Reagent: Hot Concentrated sulfuric acid
Conditions:180 degrees C (under reflux),

Question 22

Outline step 1 in the production of cyclohexene from cyclohexanol

Answer 22

Step 1: Distillation:

• Add concentrated sulfuric acid and cyclohexanol to a round bottomed flask.
• Add several anti-bumping granules to allow for a smooth boiling process
• Use a heating mantle to warm the reactants up to 83C (B.P of cyclohexanol)
• Chemicals with B.P less than 83C will evaporate, enter the condenser ,cool down and condense back into a liquid
• Product is then collected in a conical flask, yet this product will still have small amounts of impurities such as unreacted cyclohexanol and water

Question 23

What is the purpose of adding anti bumping granules during distillation

Answer 23

Allows for a smooth boiling process by preventing large bubbles from forming

Question 24

What is the boiling point of cyclohexanol

Answer 24

83 degrees C

Question 25

Why don't we use a Bunsen burner when distilling cyclohexanol

Answer 25

Cyclohexanol is flammable

Question 26

Outline step 2 in the production of cyclohexene from cyclohexanol

Answer 26

Step 2: Separation: - Add the products from step 1 to a separating funnel and add water to dissolve soluble impurities (creating an an aqueous solution) - Let the solution to settle, forming 2 layers - top layer being impure cyclohexene, bottom layer being an aqueous solution of water soluble impurities - Drain the aqueous layer off by releasing the bottom layer from the funnel

Question 27

When we heat cyclohexanol, what do we get

Answer 27

Impure cyclohexene

Question 28

Outline step 3 in the production of cyclohexene from cyclohexanol

Answer 28

Step 3: Purification: - Take the impure cyclohexene from step 2 and add back into a round bottom flask - Add the drying agent: anhydrous CaCl2/CaSO4, which will remove any aqueous substances still remaining - INVERT the flask and leave it for 20-30 mins - Keep adding the drying agent until there is no clumping, and there are only free moving grains of CaCl2/CaSO4 and the solution is clear, which means all the water has been removed from the sample

Question 29

What are the conditions required for the hydration of ethene to form ethanol

Answer 29

high temperature 300 °C high pressure 70 atm strong acidic catalyst of conc H3PO4

Question 30

Outline and name the mechanism for the formation of ethanol via the hydration of ethene

Answer 30

Electrophilic Addition

Question 31

What are the 2 ways of producing ethanol

Answer 31

Hydration of ethene (from crude oil) Fermentation of glucose

Question 32

What are the conditions for the fermentation of glucose

Answer 32

Yeast Anaerobic conditions Temperature of 30-40 degrees C

Question 33

Write the equation for the formation of ethanol via fermentation of glucose

Answer 33

Question 34

What is the role of yeast in the fermentation of glucose

Answer 34

Enzyme

Question 35

Sketch a graph showing how temperature effects the rate of fermentation of glucose

Answer 35

Question 36

After we have the obtained the products from the fermentation of glucose, what process do we use to obtain pure ethanol

Answer 36

Fractional distillation

Question 37

Why is fermentation done in anaerobic conditions

Answer 37

The presence of air can cause extra reactions to occur. O2 in air oxidises the ethanol produced to ethanoic acid (vinegar)

Question 38

What are 2 advantages of producing ethanol via the fermentation glucose

Answer 38

- Sugar is a renewable resource - Cheap equipment

Question 39

What are 2 disadvantages of producing ethanol via the fermentation glucose

Answer 39

- Ethanol made is not pure and needs purifying by fractional distillation - Depletes land used for growing food crops

Question 40

What are 2 advantages of producing ethanol via the hydration of ethene

Answer 40

*faster reaction *purer product

Question 41

What are 2 disadvantages of producing ethanol via the hydration of ethene

Answer 41

*high technology equipment needed (expensive initial costs) *ethene is non-renewable resource

Question 42

What is a biofuel

Answer 42

A biofuel is a renewable energy source made from dead biological matter

Question 43

Give an example of a biofuel

Answer 43

Ethanol

Question 44

What are 2 advantages of biofuels

Answer 44

- They are renewable so more sustainable than crude oil - Biofuels are almost carbon neutral

Question 45

What are 2 disadvantages of biofuels

Answer 45

- Expensive to convert existing petrol engines to take fuels with higher concentrations of ethanol - Land that could be used to grow food is instead used to make fuel which could cause food shortages in local communities - Loss of habitat/biodiversity to grow crops

Question 46

Give 2 reasons why biofuels not 100% carbon neutral

Answer 46

Fossil fuels are burnt to transport biofuels which releases CO2 Fossil fuels are used to make fertilisers to put the crops used to make biofuels, which releases CO2 Machinery is required to harvest the crop which releases CO2

Question 47

Write equations displaying how ethanol produced by fermentation is a carbon neutral process

Answer 47

Question 48

Give an example of a crop used to make biofuels

Answer 48

Sugar cane

Question 49

What 3 things can alcohols be oxidised to form

Answer 49

Aldehydes Ketones Carboxylic acids

Question 50

What can primary alcohols be oxidised to form

Answer 50

Aldehydes then carboxylic acids

Question 51

What can secondary alcohols be oxidised to form

Answer 51

Ketones

Question 52

What is the only way to oxidise a tertiary alcohol

Answer 52

Tertiary alcohols are not easily oxidised. Cant be oxidised using dichromate, only by burning them yet this doesn't produce any useful products so no point

Question 53

What is the conditions and reagent required for the oxidation of primary alcohols to produce a carboxylic acid

Answer 53

Reagent: potassium dichromate(VI) solution and dilute sulfuric acid Conditions: use an excess of dichromate, and heat under reflux (can then distil to separate products)

Question 54

What is the conditions and reagent required for the oxidation of secondary alcohols to produce a ketone

Answer 54

Reagent: potassium dichromate(VI) solution and dilute sulfuric acid Conditions: use an excess of dichromate, and heat under reflux

Question 55

How do we represent an oxidising agent when writing an equation for the oxidation of an alcohol

Answer 55

[O]

Question 56

If we want only an aldehyde when oxidising a primary alcohol, what can we do

Answer 56

Do not use an excess of dichromate, or heat under reflux

Question 57

What is the observation when primary alcohols are oxidised to form a carboxylic acid

Answer 57

The orange dichromate ion (Cr2O72-) reduces to the green Cr 3+ ion Orange to green

Question 58

What is the observation when secondary alcohols are oxidised to form a ketone

Answer 58

The orange dichromate ion (Cr2O72-) reduces to the green Cr 3+ ion Orange to green

Question 59

Write the an equation for the reaction using displayed formula showing the formation of a carboxylic acid from propan-1-ol

Answer 59

Question 60

Write the equation for the reaction using displayed formula showing the formation of a ketone from propan-2-ol

Answer 60

Question 61

What is the conditions required for the oxidation of primary alcohols to produce an aldehyde

Answer 61

Reagent: potassium dichromate(VI) solution and dilute sulfuric acid Conditions: Do not use an excess of dichromate, or heat under reflux

Question 62

How can we extract an aldehyde produced from the oxidation of a primary alcohol

Answer 62

We have to separate the aldehyde from the oxidising agent. We can distil the mixture since aldehydes have a lower boiling point than alcohol

Question 63

Other than aldehydes, carboxylic acids and ketones, what other product do we always form when oxidising an alcohol

Answer 63

Water

Question 64

What is the test for carboxylic acids

Answer 64

Addition of sodium carbonate. It will fizz and produce carbon dioxide if a carboxylic acid is present

Question 65

What 2 things can we use to distinguish between aldehydes and ketones

Answer 65

Fehling's solution Tollens reagent

Question 66

What is the role of both Fehling's solution and Tollens reagent reagent when distinguishing between aldehydes and ketones

Answer 66

They are oxidising agent They oxidise aldehydes but not ketones

Question 67

What does Fehling's solution consist of

Answer 67

Blue solution as it contains Cu2+

Question 68

What are the steps and positive test for the use of Fehling's solution to distinguish between aldehydes and ketones

Answer 68

If we add WARM Fehling's to: Aldehyde: Blue to brick red (Cu₂O is the red) Ketone: Remains blue

Question 69

What is the formula for tollens reagent

Answer 69

(Ag(NH3)2)+

Question 70

What are the steps and positive test for the use of tollens reagent to distinguish between aldehydes and ketones

Answer 70

If we add WARM tollens to: Aldehyde: Tollens is reduced to Ag which forms a silver mirror that coats the inside of the flask Ketone: No silver mirror formed

Question 71

What is the test for alcohols

Answer 71

Acidified K2Cr2O7 goes from orange to green in OH-

Question 72

Sketch the apparatus when filtering under reduced pressure (Buchner aparatus)

Answer 72