Haloalkanes

Question 1

What is the general formulae of haloalkanes?

Answer 1

Cn H2n+1 X

Where x= halogen

Question 2

Why is a carbon-halogen bond polar?

Answer 2

Halogen atoms are more electronegative than carbon atoms so the electron pair is therefore closer to the halogen atom.

Question 3

What is a nucleophile?

Answer 3

An electron pair donor

Question 4

What are the 4 nucleophiles?

Answer 4

1. Hydroxide ions :OH-
2. Water molecules, H2O:
3. Ammonia, :NH3
4. Cyanide, :C-N

Question 5

What is nucloephillic substitution?

Answer 5

The nucleophile replaces the halogen in a substitution reaction producing a product with a new functional group.

Question 6

Describe what happens during the hydrolysis of a haloalkane.

Answer 6

1. A lone pair of electrons on the hydroxide ion is attracted and donated to the slightly positive carbon atom
2. A new bond is formed between these oxygen of the hydroxide ion and the carbon atom
3. The carbon-halogen bond breaks by heterolytic fission forming a new alcohol and a halide ion

Question 7

What can we predict about reaction rates from different carbon-halogen bonds?

Answer 7

1. C-I bond is the weakest so less energy is required for it to be broken so iodoalkanes react the faster than bromoalkanes
2. C-I > C-Br < C-Cl
3. Fluoroalkanes are unreactive as the bond strength is too high so requires a high quantity of energy

Question 8

What experiment can be used to measure the rate of reaction of primary haloalkanes?

Answer 8

• Add silver nitrate to the haloalkanes solution and record the time taken for the precipitate to form
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