Haloalkanes Flashcards
Nucleophile
An electron pair donor
Primary haloalkanes
Carbocation formed would be attached to one R group. Eg. Propan-1-ol
Secondary haloalkanes
Carbocation formed if halide was removed would be attached to two R groups, so in the middle of the chain. Eg. 2-chloropropanol
Tertiary haloalkane
If halide ion was removed, carbocation formed would be attached to three R groups, eg. 2-chloro, 2-methylpropane.
Reason haloalkanes are more reactive than alkanes
Contain weaker bonds, taking less energy to break so more easily compensated by formation of new stronger bonds.
Electronegativity
The degree of attraction an atom has for a pair of electrons in covalent bond.
Hydrolysis of a haloalkane, reactants, conditions and products.
Reactants: haloalkane and aqueous NaOH
Conditions: Heat under reflux
Products: sodium halide and alcohol
In practice, use AgNO3 (aq) to act as an indicator, turning, forming a precipitate once halide ions have been released, and ethanol as a solvent.
Reflux
The continual boiling and condensing of a reaction mixture to prevent the loss of components.
Curly arrow represents…
Movement of an electron pair
Mechanism of hydrolysis of haloalkanes
Nucleophilic substitution
Strength of bonds in haloalkanes
C-I bonds are the weakest and C-Cl are the strongest. Least electronegative do not from dipoles so take less energy to break.
Ozone layer
Layer high in he atmosphere where UV can interact with gases.
O3 = O2 + O
UV is absorbed by O3 and O2, breaking the bonds, thus it can also break down DNA and other molecules so destroys life, causes mutations etc.
CFCs and HCFCs
Chlorofluorocarbons and hydrofluorochlorocarbons
Used in refrigerants and fire extinguishers as are inert.
Photodissociation of CFCs
Produces chlorine radical CF3Cl -> CF3 + Cl*
Requiring UV light.
Homolytic fission
Cl radicals…
Act as a catalyst in the breakdown of ozone
Cl+O3->ClO+O2
ClO+O3->Cl+O2
Overall: 2O3-(Cl*)->3O2
