Chapter 15: Haloalkanes 15.1-15.2)

Cn H2n+1 X X is a halogen atom

fluoro, -F chloro, -Cl bromo, -Br iodo, -I

C-X is a polar bond (halogens more electronegative than carbon) C-X bond polarity decreases down the group because the electronegativity of halogens decree from F -> I Polarity of the C-X bond attracts nucleophiles to the Cd+ atom

an atom or group of atoms that donates an electron pair to an electron-deficient centre usually electron rich and may be an negative ion

H20, NH3+, OH-, halogens

C-X bond enthalpy decreases down the group this means that iodo-, bromo-, and chloro- alkanes are the most reactive

a nucleophile replaces the halogen in the haloalkane, which is lost as a halide ion

NaOH (aq) KOH (aq)

• the OH- ion acts as a nucleophile, donating an electron pair to the d+ carbon atom • OH-nion attacks from the opposite side to the halide as to reduce repulsion • a new bond forms between the oxygen atom of the OH- ion and the carbon atom • the carbon-halogen bond breaks by heterolytic fission • an alcohol and a halide ion are formed

haloalkanes do not dissolve in water however in the presence of an ethanol solvent and aqueous silver nitrate, water acts as a nucleophile to form alcohol.

measuring and comparing the time for the silver-halide precipitate to form

idoalkanes (fastest) bromoalkanes chloroalkanes (slowest)

hydroxide, OH-, ions are nucleophiles with a lone pair of electrons on the oxygen atoms, which can be donated to from a new covalent bond. haloalkanes undergo nucleophilic substitution reactions with aqueous alkali, OH- (aq), to form alcohols.