Alcohols

Question 1

What are primary alcohols?

Answer 1

One carbon is attached to the carbon that has a hydroxyl group attached to it.

Question 2

What are secondary alcohols?

Answer 2

Two carbons are attached to the carbon that has a hydroxyl group attached to it.

Question 3

What are tertiary alcohols?

Answer 3

Three carbons are attached to the carbon that has a hydroxyl group attached to it.

Question 4

What is the mechanism for the dehydration of an alcohol to make an alkene?

Answer 4

elimination

Question 5

What conditions are needed for the dehydration of alcohols to make alkenes?

Answer 5

The alcohol is heated under reflux with concentrated sulfuric acid.

Question 6

Name and outline the mechanism for the dehydration of propane-2-ol using sulfuric acid.

Question 7

What are the products of the partial oxidation of primary alcohols?

Answer 7

aldehydes

Question 8

What conditions are needed for the partial oxidation of alcohols?

Answer 8

1. potassium dichromate
2. dilute sulfuric acid
3. warm gently and distil the products out as they are made

Question 9

What are the products of the full oxidation of primary alcohols?

Answer 9

a carboxylic acid

Question 10

What conditions are needed for the full oxidation of alcohols?

Answer 10

1. an excess of potassium dichromate
2. dilute sulfuric acid
3. heat under reflux and distil the product after the reaction has finished

Question 11

What are the products of the oxidation of secondary alcohols?

Answer 11

a ketone

Question 12

What conditions are needed for the oxidation of secondary alcohols?

Answer 12

1. Potassium dichromate and dilute sulfuric acid.
2. Heat under reflux

Question 13

How does potassium dichromate oxidise the alcohols?

Answer 13

The orange dichromate ion is reduced to a green chromium 3+ ion and this oxidises the alcohols.

Question 14

How is Tollen’s reagent used to test for aldehydes and ketones?

Answer 14

In the presence of an aldehyde, a silver mirror will form and in the presence of a ketone, there will be no change.

Question 15

What is Tollen’s reagent made out of?

Answer 15

aqueous ammonia and silver nitrate to form a complex ion. [Ag(NH3)2]+

Question 16

How does Tollen’s reagent work?

Answer 16

The silver ions are reduced to silver atoms and this causes the aldehydes to be reduced into carboxylic acids.

Question 17

How is Fehling’s solution used to test for aldehydes and ketones?

Answer 17

In the presence of an aldehyde, the blue solution will turn into a red precipitate.

Question 18

What is Fehling’s solution made out of?

Answer 18

Cu 2+ ions

Question 19

How does Fehling’s solution work?

Answer 19

The blue copper ions are reduced to form a red precipitate and the aldehydes are reduced into a carboxylic acid.

Question 20

How do you test for a carboxylic acid?

Answer 20

You add sodium carbonate and there will be fizzing as CO2 is produced.

Question 21

Why is there no reaction with the ketones?

Answer 21

The functional group does not contain hydrogen so the ketones can’t be oxidised.

Question 22

Write the equation for the production of ethanol from the fermentation of glucose.

Question 23

What conditions are needed for fermentation?

Answer 23

1. Yeast
2. No air
3. Temperatures of 30 to 40 degrees

Question 24

Why do the conditions need to be anaerobic?

Answer 24

So the ethanol isn’t oxidised into ethanoic acid.

Question 25

What are the advantages of fermentation?

Answer 25

1. Sugar is renewable 2. relatively cheap

Question 26

What are the disadvantages of fermentation?

Answer 26

1. the ethanol produced is not pure and needs to be purified 2. this is a batch process which is slow and expensive 3. uses land that could be used to grow crops

Question 26

Write the equation for the production of ethanol from ethene and steam.

Question 27

What conditions are needed for the hydration of ethene?

Answer 27

1. high temperatures of 300 degrees 2. high pressure of 70 atm 3. strong acid catalyst

Question 28

What are the advantages of the hydration of ethene?

Answer 28

1. the product made is pure 2. continuous process meaning that less manpower is needed to keep it going

Question 29

What are the disadvantages of the hydration of ethene?

Answer 29

1. ethene is not a renewable resource 2. expensive equipment needed 3. expensive to maintain high pressures

Question 30

Why can the use of ethanol as a biofuel be considered carbon neutral?

Answer 30

6 carbon molecules are taken in for photosynthesis and the production of glucose and 6 molecules of carbon dioxide are released in the combustion of ethanol. This means there is no net contribution to carbon dioxide emissions.

Question 31

Why might the use of ethanol as a biofuel not be considered carbon neutral?

Answer 31

Carbon dioxide is released when plants are watered, transportation and distilling the impure product.