Halogenoalkanes

Question 1

Polarity of halogenoalkane bonds

Answer 1

C-F extremely polar, not ionic 484
C-I almost non polar 238

Question 2

Boiling points of halogenoalkanes

Answer 2

As Mr increases the boiling points increases
So for same carbon chain length
CCl < CBr < CI
Due to stronger van Der waals forces from more electrons

Question 3

Solubility of halogenoalkanes in water

Answer 3

Insoluble/ slightly soluble in water

Question 4

How are halogenoalkanes formed

Answer 4

Free radical substitution
Using uv light

Question 5

What are the three stages in free radical substitution

Answer 5

Initiation (breakdown of diatomic halogen into free radicals)
Propagation (reaction of free radical with hydrocarbon chain x2 to regenerate free radical)
Termination (reaction of two free radicals)

Question 6

Ozone depletion

Answer 6

Cl• + O3 -> ClO• +O2
ClO• + O3 -> 2O2 + Cl•
Overall: 2O3 -> 3O2

Question 7

Nucleophic substitution reactions of halogenoalkanes

Answer 7

OH- aqueous NaOH, reflux, dissolved in small volume of ethanol, forms alcohol
CN- aqueous KCN,reflux, dissolved in small volume of ethanol, forms hydroxynitrile
NH3- concentrated NH3 solution, high pressure, dissolved in small volume of ethanol, forms amine
More likely for primary halogenoalkanes

Question 8

Elimination reactions of halogenoalkanes

Answer 8

OH- ethanolic NaOH, dissolved in small volume of ethanol
Hydroxide ions act as a base causing halogenoalkane to lose a hydrogen and halogen
Forms alkene and water
More likely for tertiary halogenoalkanes