Halogenoalkanes Nucleophilic Elimination

Question 1

What is elimination

Answer 1

The removal of a small molecule and the formation of a carbon carbon double bond

Question 2

Conditions for elimination

Answer 2

Add potassium hydroxide in ethanol with no water present and warm

Question 3

Process of elimination

Answer 3

OH- acts as a base and removes a hydrogen from the carbon neighbouring the carbon bonded to the halogen resulting in double bond forming between the carbons and heterolytic bond breaking of the carbon halogen bond releasing the halogen ions and water to form an alkene

Question 4

When can there be a mixture of elimination products

Answer 4

If carbon chain is four or more carbon atoms in length and the halogen not attached to the terminal carbon a mixture of positional isomers may be formed

Question 5

What temperature is elimination favoured

Answer 5

Hotter temperatures

Question 6

When is substitution favoured

Answer 6

At lower temperatures

Question 7

Is elimination more or less likely with tertiary and why

Answer 7

More likely due to steric hindrance
-react in elimination reaction with hydroxide ions more often than primary as the hydroxide group is blocked by the bulky R groups(steric hindrance) and the hydrogen that’s exposed is the one that is attacked rather than the carbon in the centre, in primary the hydroxide ion is much less hindered

Question 8

Conditions that favour elimination

Answer 8

-ethanol solvent so no water
-higher temperatures
-concentrated solution of sodium hydroxide

Question 9

Conditions that favour substitution

Answer 9

-lower temps
-more water in ethanol solvent
-less concentrated solution of sodium hydroxide

Question 10

Substitution or elimination more likely in primary

Answer 10

Substitution

Question 11

Substitution or elimination in secondary

Answer 11

Both elimination and substitution