3.3.5 Alcohols

Question 1

Order of stability carbocation and why

Answer 1

Tertiary>secondary>primary
Tertiary has greater positive inductive effect

Question 2

Explain why ethanol has a higher boiling point than ethane

Answer 2

Contain hydrogen bonding which is stronger IMF than Van fer Waals

Question 3

Which type of cracking produces higher proportion of alkenes + conditions

Answer 3

Thermal
High temperatures + pressure

Question 4

Oxidisation reaction of primary alcohol

Answer 4

Reacts with Potassium dichromate [O] and sulphuric acid to form aldehyde + water (heat + distill off product)

Question 5

Oxidisation reaction of aldehyde

Answer 5

Reacts with potassium dichromate and sulphuric acid [O] (or Fehling’s solution/Tollen’s reagent) to form carboxylic acid

Question 6

Oxidisation reaction of secondary alcohol

Answer 6

Reacts with Potassium dichromate [O] and sulphuric acid to form ketone + water (heat or reflux)

Question 7

Oxidisation reaction of tertiary alcohols and ketones

Answer 7

Not easily oxidised unless you set fire to them
C-C bonds not easily broken

Question 8

Dehydration of alcohols

Answer 8

Elimination reaction
Alcohols reacted with hot, concentrated H2SO4 at 180°C to produce alkene and water

Question 9

One reason, other than incomplete combustion or heat transfer to the atmosphere, why the student’s value for the enthalpy of combustion of methanol is different from that in a Data Book.

Answer 9

Evaporation of alcohol
Experiment not done under standard conditions
Heat capacity of copper not taken into account

Question 10

What reagent is used to convert a carbonyl compound into an alcohol ?

Answer 10

NaNH4

Question 11

3 conditions necessary for fermentation

Answer 11

Yeast
Anaerobic
Warm

Question 12

2 advantages of fermentation over hydration of ethene

Answer 12

Renewable
Cheaper equipment

Question 13

Structure of potassium dichromate

Answer 13

K2Cr2O7

Question 14

How are alcohols produced industrially

Answer 14

Hydration of alkenes with acid catalyst

Question 15

Describe how ethanol is produced from ethene

Answer 15

Reaction with steam using phosphoric acid catalyst

Question 16

Describe how ethanol is produced by fermentation

Answer 16

Glucose from plant material is converted into ethanol and carbon dioxide

Question 17

Describe how ethanol produced industrially by fermentation is separated by fractional distillation + how it can be used

Answer 17

Liquids with different boiling points in mixture evaporate at different temperatures
Used as biofuel

Question 18

Explain the term biofuel

Answer 18

Fuels produced from natural products
Often plant biomass containing carbohydrates
Renewable + theoretically carbon neutral

Question 19

Describe how alkenes can be used to produce addition polymers without using monomers derived from crude oil

Answer 19

Double bonds of the alkene molecules are broken and new single bonds are formed between the carbon atoms of adjacent monomers