3.3- halogenoalkanes

Define halogenoalkanes

Alkanes with 1/more halogens attached to it

Name this halogenoalkane

Trifluoromethane

Name this halogenoalkane

2-chloropropane

Name this halogenoalkane

1-bromo-1,1-dichloro-3-iodoethane

Describe the boiling point trend of halogenoalkanes

Increases down the group

Why do the boiling points increase down the group

\-down the group electrons increase

\-stronger van de waals between molecules

\-more energy needed to overcome forces

Define a nucleophile

Substance that is an electron pair donor

Give examples of nucleophiles

\-ammonia

\-hydroxide ions

\-cyanide ions

How do halogenoalkanes react with hydroxide ions

Via nucleophilic substitution

Conditions for nucleophilic substitution

\-warm aqueous sodium hydroxide

\-carried out under REFLUX

How do halogenoalkanes react with cyanide ions

Halogenoalkanes react with cyanide ions to make nitriles

Conditions for nucleophilic substitution with cyanide ions

\-warm ethanoic potassium cyanide

\-carried out under REFLUX

Describe trend of halogenoalkane activity

Reactivity increases down the group

What determines reactivity

Bond enthalpy

Describe reaction between hydroxide ions and halogenoalkanes

Elimination using ethanol solvent

Conditions for the reaction with hydroxide ions

\-warm ethanol in sodium hydroxide

\-carried out under REFLUX

How does UV radiation break down CFCs

Breaks C-Cl bonds, radicals are formed and catalyse the break down of ozone

Why are C-Cl bonds broken easiest in CFCs

Lowest bond enthalpy

How does CFCs destroy ozone

Breaks down to form chlorine radicals that catalyse the breakdown of ozone

What is an alternative to CFCs

HFCs and hydrocarbons