Halogenoalakanes

Properties:

• Let X = halogen, C-X bond where C is partially (+) and X is partially (-), so has dipole-dipole and van der waals forces

• Boiling point: increases with increased chain length, and increases with halogen down the group (increased van der waals)

The C-X bond (where X = halogen)

• If the C-X bond is higher in polarity (C-F > C-I) then higher rate of reaction. So, can be attacked by reagents that are electron rich known as nucleophiles (an electron pair donor)

• If the C-X bond has lower enthalpy then higher rate of reaction. Iodo-compounds have C-I bond with lowest enthalpy less energy to break bond, so more reactive.

Define Nucleophile

Nucleophiles are negatively charged particles that have attracted towards slightly positive charge. For example, ^-:OH (hydroxide ion), :NH₃ (Ammonia), ^-:CN (Cyanide)

Formation of Alcohol from Halogenoalkane

• Conditions: Warm and aqueous

• Reaction mechanism: Nucleophillic substitution

• Form: Alcohol

• Reagent: KOH or NaOH

• Nucleophile: ^-:OH

The formation of a nitrile from Halogenoalkane

• Conditions: warm and alcoholic

• Reaction mechanism: Nucleophillic substitution

• Form: Nitrile

• Reagent: KCN (potassium cyanide)

• Nucleophile: ^-:CN

• KEY: There is an extra C when adding ^-:CN to carbon chain.

The formation of amine from Halogenoalkane

• Conditions: warm, Ethanolic and excess

• Reaction mechanisms: Nucleophillic substitution

• Form: Amine

• Reagent: Ammonia

• Nucleophile: :NH₃

• KEY: N is unstable when having 4 bonds so needs to react again

  • THE POSITIVE CHARGE ON THE INTERMEDIATE IS ON THE NITROGEN

Define Base

A proton acceptor

Formation of Alkene from Halogenoalkane

• Conditions: Hot and ethanollic

• Reaction mechanism: Elimination

• Form: Alkene

• Reagent: NaOH or KOH

• Base: ^-:OH

• KEY: The arrow travels from the base to the hydrogen adjacent to the halogen