Haloalkanes Flashcards
Define nucleophile
An electron pair donor
What does hydrolysis of haloalkanes produce?
An alcohol
Describe the process of hydrolysis of haloalkanes
The nucleophile OH-, approaches the σ+ carbon in the haloalkane from the opposite side as to the halogen to minimise repulision between the σ- halogen and the OH-.
The lone pair of electrons from the hydroxide ion is donated to the σ+ carbon atom.
A new bond is formed between the oxygen (oh the hydroxide) and the carbon atom.
The carbon halogen bond breaks by heterolytic fission producing a halide ion and alcohol.
what is used to produce OH - ions for hydrolysis of haloalkanes
water or hydroxide solution (e.g. aquesous NaOH)
During hydrolysis of a haloalkane what type of fission occyrs to break the carbon halogen bond?
Heterolytic fission
What can be done to speed up hydrolysis of a haloalkane?
Heating the reaction under reflux to speed it up.
What does the rate of hydrolysis depend on with different reactants?
The rate of hydrolysis depends on the strength of the carbon halogen bond in the haloalkane.
Describe why Iodoalkanes have a faster rate of reaction of hydrolysis in comparison to Chloro- or Bromo- alkanes
Iodoalkanes react faster as less energy is needed to break the C-I bond than the C-Cl or C-Br bonds.
Why do Fluoroalkanes not Hydrolyse?
the carbon fluorine bond is too strong and requires to much energy to overcome.
What happens to the rate of hydrolysis as the carbon halogen bond strength decreases?
Rate of hydrolysis increases
What is added to measure the rate of hydrolysis?
Aqueous silver nitrate AgNO3
an ethanol solvent is also used instead of water.
Describe what occurs when measuring the rate of hydrolysis for a reaction
Haloalkane is added to an ethanol solvent, AgNO3 is then added, the Ag+ ions react with the disaplced halide ions one hydrolysis has occured, producing a precipitate, time taken for the precipitate to form is measured and compared for other haloalkanes. Faster time = faster rate of reaction.
Why is ethanol solvent used instead of water for measuring the rate of hydrolysis of haloalkanes?
Haloalkanes are insoluable in water and mess up the measuring of the precipitate formed. Haloalkanes are soluable in ethanol.
What are organohalogen compounds
Compounds which contain at least one halogen atom joined to a carbon chain.
Desrcibe how CFC molecules destroy the ozone
CFCs are stable due to their strong carbon halogen bonds, however one in the atmosphere the Uv radiation provides enough energy to break down the CFCs by homolytic fission.
The halogen radicals formed are very reactive and break down ozone. In a propigation reaction, can be repeated over and over as halogen radical is reformed.
