3.3 halogenoalkanes

primary halogenoalkane

secondary halogenoalkane

tertiary halogenoalkane

what type of reactions do halogenoalkanes undergo (2)

nucleophilic substitution

elimination

what is substituted in nucleophilic substitution

swapping a halogen atom for another atom

what nucleophiles are using in nucleophilic substitution

electron pair donators

e.g :OH^- :NH₃ CN^-

what do nucleophiles always have

a lone pair

the mechanism of nucleophilic substitution

which halogenoalkanes are the fastest to substitute and why

iodoalkanes as they are most reactive

hydrolysis

splitting of a molecule by a reaction with water

what forms when aqueous sliver nitrate is added to a halogenoalkane

silver halide precipitate

nucleophilic substitution with aqueous hydroxide ions

product, reagent, conditions

product - alcohol

reagent - KOH or NaOH

conditions - aqueous solution, warm

reagent - nucleophile :OH^-

mechanism of 1-bromopropane with KOH

nucleophilic substitution with cyanide ions

product, reagent, conditions

product - nitrile

reagent - KCN dissolved in ethanol/water

conditions - heat under reflux

nucleophile, :CN^-

mechanism of 1-bromopropane with KCN

nucelophilic substitution with ammonia

product, reagent, conditions

product - amine

reagent - NH₃ dissolved in ethanol

conditions - heating under pressure

nucleophile :NH₃

mechanism of 1-bromoproane and NH₃

what is an elimination reaction

removal of a small molecule from the organic molecule

elimination of halogenoalkanes with alcoholic hydroxide ions

product, reagent, conditions

product - alkenes

reagent - KOH NaOH

conditions - in ethanol, heat

base, :OH^-

mechanism of 1-bromopropane and KOH

what type of reaction do primary halogenoalkanes lean to

nucleophilic substitution

what type of reaction do tertiary halogenoalkanes lean to

elimination

uses of chloroalkanes and chlorofluoroalkanes

solvents

why is the formation of ozone beneficial

absorbs UV radiation

how are chlorine atoms formed in the upper atmosphere

when UV radiation causes C-Cl bonds in CFCs to break

what do chlorine atoms do

catalyse the decomposition of ozone and contribute to the hole in the ozone layer

equation for the decomposition of ozone layer

Cl radical is regenerated so can destroy thousands of ozone moleules

what has happened to the use of CFCs now

banned

developed chlorine free compounds HFCs

CH₂FCF₃ is used for refrigerators and air conditioners

why is the C-F bond not affected by UV light

it is stronger than the C-Cl bond