Halogenoalkanes

Question 1

Describe the bond polarity of halogenoalkanes

Answer 1

Halogens are more electronegative than carbons, the difference in electro negativity causes a polar bond.

Question 2

Bond enthalpy of halogenoalkanes

Answer 2

Bonds get weaker down the group as size of the halogen increases so the attraction between the electrons and the halogen decrease. This makes halogenoalkanes at the bottom are more reactive.

Question 3

What is a nucleophile

Answer 3

A negatively charged ion or a delta negative atom with a lone pair of electrons which donates a pair of electrons

Question 4

3 nucleophiles of nucleophillic substitution

Answer 4

OH-, NH3, CN-

Question 5

Condition of nucleophilic substitution

Answer 5

OH-: heat under reflux + aqueous conditions
CN-: heat under reflux + ethanolic conditions
NH3-: excess conc ammonia

Question 6

Conditions of elimination

Answer 6

NAOH/KOH dissolved in ethanol + heat

Question 7

What are CFCs

Answer 7

Compounds containing chlorine, fluorine and carbons but no hydrogen.

Question 8

What is the problem with CFCs

Answer 8

They catalyse the breakdown of ozone in the atmosphere

Question 9

equations for the breakdown of ozone

Answer 9

Cl. + O3 -> ClO. + O2
ClO. + O3 -> Cl. + 2O2

Question 10

Overall equation for the breakdown of ozone

Answer 10

2O3 -> 3O2

Question 11

What are the alternatives to CFCs

Answer 11

HFCs - do not harm the ozone layer as they do not contain chlorine but are greenhouse gases.
Hydrocarbons - they decompose quickly but are flammable and contribute to greenhouse gas emission