Unit 2

Question 1

What are some physical properties of E-Z isomerism? Explain:

Answer 1

In general the shape of E molecules means they can fit closer together meaning they have stronger intermolecular forces and higher melting points

Question 2

What is the effect of branching on boiling temperature?

Answer 2

When there is more branching there is a higher chance of it becoming spherical which has a smaller surface area than if it was straight chains, this smaller surface area gives a smaller area of contact so lower boiling temp.

Question 3

Describe the steps of Halogenation:

Answer 3

1. Initiation= Ultraviolet light has sufficient energy to break the Cl-Cl bond, meaning homolytic bond fission occurs forming radicals.
2. Propagation= Uses a radical as a reactant which forms a radical in the products meaning that the reaction continues (chain reaction)
3. Termination= Propagation continues until two radicals meet which stops it

Question 4

How to test for a Alkene?

Answer 4

Discolouration of brown bromine water.

Question 5

What is the other reaction used with electrophilic addition?

Answer 5

Hydrogenation= catalysed by nickel. very important because liquid vegetable oils contain polyunsaturated bonds and can be made saturated by the addition on hydrogen, making more solid fats.

Question 6

Describe how you can prepare alcohols from halogenoalkanes:

Answer 6

Halogenoalkane will react with hydroxide ions in nucleophilic substitution, this can be done under reflux.

Question 7

What are the effects of changing the halogen when preparing alcohols?

Answer 7

Bond strength dominates electronegativity meaning that iodo is fastest because it has the weakest bond with hydrogen.

Question 8

What is the test for halgenoalkanes?

Answer 8

Neutralise sodium hydroxide with nitric acid (would interfere)

Add sliver nitrate

to distinguish between colours (Dilute ammonia = chlorine, conc = bromine, no dissolve = iodine)