Halogeno-Alkenes

with Aqueous Alkali

• Nucleophilic Substitution

• Halogen replaced with OH-

• Forms alcohols

• OH- is the nucleophile

• More electronegative the halogen = less reactive due to bond strength

with Ethanoic Cyanide

• Nucleophilic Substitution

• KCN in ethanol.

• Halogen replaced by CN-

• Forms nitriles

• CN- is the nucleophile

with Ethanoic Ammonia

• Nucleophilic Substitution

• Excess Ammonia NH3 (Must be excess otherwise the primary amines that form can react further to form secondary amines)

• Heat + Pressure

• Forms amines

Reflux

Heating a volatile liquid by condensing it as it evaporates.

with Hydolysis

• Nucleophilic Substitution

• Adding Water

• Forms alcohols and Hydrogen Halides

• Less Nucleophilic: Slower than OH-

SN1

• Nucleophilic Substitution Mechanism

• For Tertiary and Secondary Halogenoalkanes

• Steps:

  • Electronegativity difference between C-Halogen bond creates heterolytic fission

  • Nucleophile immediately replaces halogen by bonding to carbocation

SN2

• Nucleophilic Substitution Mechanism

• Rates depends on 2 factors: Conc. of Hydroxide and Halogenoalkanes

• For Primary and Secondary Halogenoalkanes

• Steps:

  • Nucleophile donates electron pair to halogen

  • while Heterolytic fission is occurring between carbon and halogen

  • Intermediate: nucleophile bonds to and halogen breaks away from carbon at the same time

  • Halogen Halide is left over

with Ethanoic Alkali

• NaOH

• OH- accepts H+ forming H20

• C-Halogen bond breaks heterolytically

• Halogen and Na bond forming NaX

• Forms Alkenes

Use of Halogenoalkanes

• C-F & C-Cl bonds are inert:

  • Use in anesthetics

  • Teflon (durable under high heat)

• CFC (Chlorofluorocarbons):

  • non-flammable, non-toxic, inert

  • Aerosol Propellants, refrigerants

  • Can create FREE RADICALS in the atmosphere, which react and destroy ozone.

• HFC & HFE (hydrofluoro-carbons/ethanes):

  • Break down in the low atmosphere before destructing ozone