3.3.3 - Halogenoalkanes

Question 1

Boiling point trend of haloalkanes + reason

Answer 1

Increases down the group, more electrons = stronger VdW forces

Question 2

What is a nucleophile?

Answer 2

An electron pair donor

Question 3

Why does nucleophilic substitution occur?

Answer 3

Polar bond between carbon and halogen attacked by nucleophile.

Question 4

Conditions for nucleophilic substitution (2)

Answer 4

• Warm, aqueous NaOH/KCN
• Reflux

Question 5

Conditions for ammonia nucleophilic substitution (2)

Answer 5

• Heated
• Excess ethanolic ammonia

Question 6

Ammonia nucleophilic substitution mechanism

Answer 6

NH3 reacts with haloalkane carbon, hydrogen from NH3 taken by excess NH3 to form NH4 (diagram)

Question 7

Halogenoalkanes reactivity trend

Answer 7

Increases down the group, as bond enthalpy down the group decreases

Question 8

Elimination reaction conditions to form alkene (2)

Answer 8

• Warm ethanolic KOH
• Reflux

Question 9

Elimination reaction mechanism (think OH-)

Answer 9

OH attacks adjacent carbon, forms alkene + H2O + halogen ion (diagram)

Question 10

Difference between elimination and substitution (solvent)

Answer 10

Substitution - solvent is water
Elimination - solvent is ethanol

Question 11

Ozone decomposition overall reaction

Answer 11

Overall reaction - 2O3 - 3O2

Question 12

Decomposition of ozone with chlorine radical

Answer 12

Cl@ = intermediate catalyst
Cl@ + O3 = ClO@ + O2
ClO@ + O3 = Cl@ + 2O2

Question 13

Test for halogens

Answer 13

Add aqueous silver nitrate

Question 14

Test for halogens results

Answer 14

Chloride - white
Bromide - cream
Iodide - yellow