Alcohols

Question 1

what’s general formula for alcohols

Answer 1

CnH2n+1OH

Question 2

what are the classifications of alcohols

Answer 2

primary
secondary
tertiary

Question 3

what does the classification of alcohols relate to

Answer 3

the number of carbon atoms directly attached to the carbon atom carrying the OH group

Question 4

name the 2 methods ethanol can be produced

Answer 4

1) fermentation of glucose

2) direct hydration of ethene

Question 5

what does fermentation of glucose do

Answer 5

this process converts sugars such as glucose into ethanol and co2 using the enzymes in yeast cells

Question 6

what 3 conditions are needed for the conversion of glucose into ethanol via fermentation

Answer 6

• yeast provides enzymes which is the catalyst
• 37° so enzymes do not denture
• absence of O2 (anaerobic respiration)

Question 7

what are the advantages of fermentation of glucose into ethanol

Answer 7

1) low energy input

2) sugar cane is a renewable source

3) ethanol made this way is said to be a biofuel ( derived from plants and animals )

4) it is said to be CARBON NEUTRAL ( the CO2 released when burnt is equal to CO2 taken in photosynthesis)

Question 8

give definition of carbon neutral

Answer 8

no net emissions of carbon dioxide to atmosphere

Question 9

is fermentation of glucose actually carbon neutral and why

Answer 9

no

bc addition CO2 will be made during burning fossil fuels for transportation and harvesting sugar cane crops

Question 10

give disadvantages of fermentation

Answer 10

1) low yield

2) product is impure (further distillation required)

3) slow rate of reaction

4) batch process

5) environmental issues with loss of habitats and deforestation for producing crops

6) the land could be used for food production

Question 11

what are the 3 conditions for direct hydration of ethene

Answer 11

• steam
• heat
• concentrated H2SO4 catalyst

Question 12

what are the advantages of direct hydration of ethene

Answer 12

1) high yield and purity

2) continuous process

3) fast rate of reaction

Question 13

what are the disadvantages of direct hydration of ethene

Answer 13

1) high energy input

2) ethene is obtained from crude oil which is a non renewable source

Question 14

what mechanism is direct hydration of ethene

Answer 14

electrophillic addition

Question 15

what reaction to alcohols undergo to form alkenes

Answer 15

alcohols are dehydrated to form alkenes in elimination mechanism

Question 16

what are the conditions to form alkenes from alcohols in elimination reaction

Answer 16

heat

concentrated sulphuric acid or phosphoric acid

Question 17

what is the oxidising agent for alcohols

Answer 17

acidified potassium dichromate (VI)

Question 18

what colour does acidified potassium dichromate (VI) change to when it acts as an oxidising agent

Answer 18

orange to green

Question 19

what bond is formed when alcohols are oxidised

Answer 19

a carbonyl bond c=o

Question 20

what are primary alcohols oxidised to and what conditions ?

Answer 20

aldehydes

distillation f

Question 21

what are aldehydes oxidised to and under what conditions

Answer 21

carboxylic acids

reflux apparatus conditions

Question 22

what are secondary alcohols oxidised to and under what conditions

Answer 22

ketones

under distillation apparatus

Question 23

rank aldehydes, alcohol and carboxylic acids by boiling point and why

Answer 23

aldehydes

alcohol

carboxylic acids

least aldehyde) permanent dipole-dipole forces between molecules are
weaker than hydrogen bond

middle alcohol) hydrogen bonds between the molecules

highest carboxylic acids) hydrogen bonds between the molecules and is a
bigger molecule so more van der waals forces between molecules

Question 24

what are the 2 oxidising agents to differentiate between aldehydes and ketones

Answer 24

tollens reagent (silver mirror )

fehlings solution (brick red ppt)