Topic 15: Alcohols

Question 1

Alcohols

Answer 1

-OH functional group

Question 2

Fermentation

Answer 2

Makes ethanol from glucose

Question 3

Hydration of ethene

Answer 3

Adding steam to an alkene to produce an alcohol

Question 4

Fermentation equation

Answer 4

C6H12O6 —> 2C2H5OH + 2CO2

Question 5

Fermentation conditions

Answer 5

Yeast, oxygen free environment, 30-40*C

Question 6

Fermentation advantage

Answer 6

Sugar is renewable
Cheap equipment

Question 7

Fermentation disadvantage

Answer 7

Batch process
Ethanol needs distilling to purify
High labour costs

Question 8

Hydration of ethene equation

Answer 8

C2H4 + H20 <===> C2H5OH

Question 9

Hydration of ethene conditions

Answer 9

CONC. H3PO4 or CONC. H2SO4
temp 300*C
pressure 70atm

Question 10

Hydration of ethene advantages

Answer 10

Continuous
Purer product

Question 11

Hydration of ethene disadvantages

Answer 11

Ethene is non renewable - from crude oil
High equipment cost
Low labour cost

Question 12

Biofuel

Answer 12

Fuel from plants

Question 13

Ethanol as biofuel

Answer 13

Photosynthesis takes in 6 CO2 when the glucose produced is fermented to ethanol and combust 6 CO2 produced so no net release of CO2 so carbon neutral

Question 14

Photosynthesis reaction

Answer 14

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 15

Ethanol combustion reaction

Answer 15

2C2H5OH + 6O2 —> 4CO2 + 6H20

Question 16

Ethanol as a fuel 100% carbon neutral

Answer 16

No
Transport produces CO2
Machines produce CO2

Question 17

Primary alcohol oxidises into

Answer 17

Aldehyde and further to carboxylic acid

Question 18

Tertiary alcohol oxidises into

Answer 18

Can’t be oxidised

Question 19

Secondary alcohol oxidises into

Answer 19

Ketone

Question 20

Oxidising agent for alcohols

Answer 20

Acidified potassium dichromate
K2Cr2O7

Question 21

Test for aldehyde and ketone and alcohols

Answer 21

Aldehyde, primary and secondary alcohols turns from orange to green when oxidised using acidified potassium dichromate. Ketones and tertiary alcohols wont.

Question 22

Oxidation reaction of primary alcohol equation

Answer 22

C2H5OH + [O] —> CH3CHO + H2O

Question 23

Oxidation reaction of primary alcohol further equation

Answer 23

CH3CHO + [O] —> CH3COOH

Question 24

Producing only aldehyde from primary alcohol

Answer 24

Heat and distil - will evaporate and condense into new flask

Question 25

Producing carboxylic acid from primary alcohol

Answer 25

Heat under reflux - will evaporate and condense back into original pear shaped flask then distil the carboxylic acid

Question 26

Oxidation of secondary alcohol equation

Answer 26

CH3CHOHCH3 + [O] ---> CH3COCH3 + H2O

Question 27

Test for aldehyde

Answer 27

Add Tollens reagent to aldehyde silver mirror will form wont with ketone as can't be further oxidised

Question 28

Test for aldehyde (other)

Answer 28

Add Fehling's solution orange ppt for aldehyde nothing for ketone stays blue

Question 29

Dehydration of ethanol equation

Answer 29

Ethanol ---> ethene + water

Question 30

Dehydration of ethanol what happens?

Answer 30

Hydroxyl group is removed along with a hydrogen from the adjacent carbon NOT the one attached to the hydroxyl group

Question 31

Dehydration of tertiary alcohol

Answer 31

Can't happen, no H to remove from adjacent C

Question 32

Conditions and type of reaction of dehydration of alcohol

Answer 32

conc. H2SO4 elimination reaction

Question 33

Mechanism of dehydration of ethanol

Answer 33

Partial charges on hydroxyl group Arrow from lone pair to H+ New molecule Arrow from adjacent CH bond to CC bond Arrow from CO bond to positive O attached to 2 H Creates ethene and water

Question 34

Hydration of ethene mechanism

Answer 34

Arrow from double bond of ethene to H+. New molecule Carbocation made Arrow from lone pair on water molecule to carbon New molecule Positively charged water attached to molecule Arrow from O-H bond to oxygen Makes alcohol and H+