3.3 Alkenes and alcohols

Question 1

In electrophilic addition which would be the major product out of 1-bromopropane and 2-bromopropane and why?

Answer 1

2-bromopropane as it is attached to a secondary carbocation which is more stable than a primary carbocation.

Question 2

What is the step that takes ethyl hydrogen sulfate to ethanol and sulfuric acid?

Answer 2

Adding warm water or hydrolysis

Question 3

How are addition polymers formed?

Answer 3

Alkenes which have their double bonds broken form addition polymers

Question 4

What determines the properties of polyalkenes?

Answer 4

Their intermolecular forces.

Question 5

What is the only intermolecular force which acts on polymers?

Answer 5

Van der Waals forces

Question 6

What can be used to modify the properties of polymers and how do they work?

Answer 6

Plasticisers get between the polymer chains which weakens the intermolecular forces, making the plastic more flexible.

Question 7

What process turns alcohols into alkenes?

Answer 7

Dehydration by removing an water molecule from the alcohol

Question 8

What is added as a catalyst in the dehydration of alkenes?

Answer 8

Sulfuric acid (or phosphoric acid)

Question 9

Name and explain the first stage of producing cyclohexene from cyclohexanol

Answer 9

Distillation is where the mixture is heated in a round bottomed flask with carborundum boiling chips to 83°C. The cyclo- chemicals will boil. Then they are condensed using a condenser and collected in a flask.

Question 10

What do carborundum boiling chips do in the process of distillation?

Answer 10

They make the mixture boil calmly

Question 11

Name and explain the second stage of producing cyclohexene from cyclohexanol

Answer 11

Separation is where the remaining liquid is put into a separating funnel where the aqueous and oil layers will separate. The aqueous layer (water and cyclohexanol) will be drained.

Question 12

Name and explain the third stage of producing cyclohexene from cyclohexanol

Answer 12

Drain the cyclohexene into a round bottomed flask and add anhydrous CaCl₂ (a drying agent) and place a bung on the flask. After 20 mins of occasional swirling distill the liquid to get pure cyclohexene.

Question 13

What are the conditions for producing ethanol by the hydration of ethene?

Answer 13

300°C, 60 atm and a solid phosphoric(V) acid catalyst

Question 14

Why is an acid catalyst used in the process of hydration and dehydration?

Answer 14

Because acids are proton donors and protons (H⁺) are required in both processes

Question 15

What is the ideal temperature for fermentation of glucose to produce ethanol?

Answer 15

30°C-40°C

Question 16

What else is needed in the fermentation process?

Answer 16

Yeast and anaerobic conditions

Question 17

What needs to be done when fermentation is complete?

Answer 17

The ethanol needs to be purified

Question 18

What are 2 advantages and 2 disadvantages with using ethanol as a biofuel?

Answer 18

Pros: Renewable, carbon neutral
Cons: current engines need to be modified to use it, the land used to grow sugar for fermentation could of been used to grow crops for food

Question 19

What do oxidised primary alcohols produce?

Answer 19

Aldehydes and then to carboxylic acids

Question 20

What do oxidised secondary alcohols produce?

Answer 20

Ketones

Question 21

What are tertiary alcohols oxidised to?

Answer 21

They can’t be oxidised

Question 22

What is an aldehyde?

Answer 22

A carbon on the end of a chain with a double bond to an oxygen molecule

Question 23

What is a ketone?

Answer 23

A carbon chain where one of the inner carbons has a oxygen double bond

Question 24

What is a carboxylic acid?

Answer 24

A carbon chain with an oxygen double bond and a OH group on the last carbon

Question 25

What does heating under reflux mean?

Answer 25

Where you increase the temperature of an organic reaction with a condenser at the top so you don’t loose any volatile solvents, reactants or products.

Question 26

What are all alcohols oxidised with?

Answer 26

Potassium dichromate and sulfuric acid

Question 27

How are solutions tested to see if they are an aldehyde or a ketone?

Answer 27

They are mixed with an oxidising solution as aldehydes are easily oxidised whereas it’s much harder to oxidise a ketone. Cu²⁺ which is deep blue will turn brick red when oxidised.

Question 28

Which is more stable, primary or tertiary carbocations?

Answer 28

Tertiary