MECHANISMS: Nucleophilic Sub + Elimination

Question 1

Outline nucleophilic substitution reactions with haloalkanes and give the nucleophiles

Answer 1

nucleophiles:
ethanolic, heat KCN/HCN
KOH/NaOH, aqueous, warm
excess NH3, heat
(to make amines, alcohol and nitriles)

Question 2

explain why the carbon–halogen bond enthalpy influences the rate of reaction.

Answer 2

The carbon-halogen bond has to be broken during the reaction.

The harder the bond is to break (the higher the bond enthalpy) the slower the haloalkanes react.

Question 3

State a reagent that occurs in elimination and nucleophilic substitution and how does it act as a base and nucleophile?

Answer 3

reagent: KOH

elimination: alcoholic KOH, heat under reflux

nucleophilic substitution: aqueous KOH, heat under reflux

KOH acts as a base and nucleophile because KOH can attract the H+ in elimination to form an alkene and it can donate its pair of electrons to the delta positive C to make an alcohol in nucleophilic substitution.

Question 4

Outline the mechanism and reagents for elimination of haloalkanes to alkenes

Answer 4