Alcohols

Question 1

DEHYDRATION OF ALCOHOLS
What is the reagent, condition, mechanism, and equation?

Answer 1

Reagent: concentrated sulfuric acid catalyst
Condition: 150-200 C
Mechanism: Elimination
Equation: Ethanol —> ethene + water

Question 2

ALCOHOL PRODUCTION (HYDRATION OF ALKENES)
What are the conditions, equation, and reaction mechanism for this ?

Answer 2

Conditions: concentrated phosphoric acid catalyst, High T (300 C), High P (70 atm)
Equation: Ethene + steam —> ethanol
Reaction mechanism: Addition

Question 3

ALCOHOL PRODUCTION (FERMENTATION)
What are the conditions and equation for this reaction?

Answer 3

Conditions: yeast in anaerobic conditions, temperatures of 30-40 C
Equation: glucose —> ethanol + carbon dioxide

Question 4

What does the term biofuel mean?

Answer 4

A fuel produced from dead biological matter such as plants.

Question 5

Ethanol as a biofuel is produced from?

Answer 5

fermentation

Question 6

What does carbon neutral mean?

Answer 6

When there is no net emissions of CO2 to the atmosphere (same amount taken in and released)

Question 7

What are the advantages of ethanol as a biofuel?

Answer 7

• Production method is carbon neutral
• Biofuels are renewable so more sustainable than crude oil

Question 8

What are the disadvantages of ethanol as a biofuel?

Answer 8

• Expensive to take fuels from petrol engines
• Land used to make food is now used to make fuels which cause food shortages

Question 9

What are the processes that produce and remove carbon dioxide (show that production of biofuel is carbon neutral)

Answer 9

1. Production of CO2 from fermentation and combustion
2. Removal of CO2 by photosynthesis

Question 10

What is the equations for production of CO2 by fermentation and combustion?

Answer 10

C6H12O6 —> 2CH3CH2OH + 2CO2 (glucose —> ethanol + carbon dioxide)

2CH3CH2OH + 6O2 —> 4CO2 + 6H2O (ethanol + oxygen —> carbon dioxide + water)

Question 11

What is the equation for removal of CO2 by photosynthesis?

Answer 11

6CO2 + 6H2O —> C6H12O6 + 6O2 (carbon dioxide + water —> glucose + oxygen)

Question 12

OXIDATION OF PRIMARY ALCOHOLS
What are the reaction and reagent for this?

Answer 12

Reaction: primary alcohol —> aldehyde —> carboxylic acid
Reagent: acidified potassium dichromate (oxidising agent)

Question 13

OXIDATION OF PRIMARY ALCOHOLS
What are the conditions to convert aldehyde to carboxylic acid?

Answer 13

• Use reflux
• Use excess oxidising agent

Question 14

OXIDATION OF SECONDARY ALCOHOLS
What are the reaction and reagent, and conditions for this?

Answer 14

Reaction: secondary alcohols oxidised —> ketones
Reagent: acidified potassium dichromate
Conditions: excess oxidising agent, heat under reflux

Question 15

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What are the observations when tollens reagent is added to aldehydes?

Answer 15

produce silver mirror

Question 16

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What are the observations when tollens reagent is added to ketones?

Answer 16

no visible change/no silver precipitate formed

Question 17

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What are the observations when fehling’s solution is added to aldehydes?

Answer 17

from blue solution to brick red precipitate

Question 18

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What are the observations when fehling’s solution is added to ketones?

Answer 18

do not react/no visible change

Question 19

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What do fehling’s solution contain?

Answer 19

Blue Cu2+ (copper) ions

Question 20

TESTS TO DISTINGUISH BETWEEN ALDEHYDES AND KETONES
What do tollens’ reagent contain?

Answer 20

mixture of aqueous ammonia and silver nitrate

Question 21

OXIDATION OF ALCOHOLS
What is the observation for the dichromate ion in potassium dichromate?

Answer 21

orange dichromate ion turns to GREEN CHROMIUM ION