Halogenoalkanes Flashcards
What order do the halogens go when naming halogenoalkanes?
Alphabetical order.
What happens to the boiling point of halogenoalkanes as you go down the group?
Increases.
Why doe boiling point of halogenoalkanes increase down the group?
*number of electrons increases
*more van der waals forces
*stronger forces
*require more energy to overcome
Why are halogenoalkanes attacked by nucleophiles?
They have a polar bond.
Why do halogenoalkanes have a polar bond?
The halogen is more electronegative that the carbon (pulls the electrons towards it).
What is a nucelophile?
An electron pair donor.
What are the three nucelophiles?
*ammonia
*cyanide
*hydroxide
What is the name of the mechanism when a nucleophile attacks a halogenoalkane?
Nucleophilic substitution.
What are the conditions of nucleophilic substitution with hydroxide?
*warm aqueous sodium hydroxide
*carried out under reflux
What does nucleophilic substitution with hydroxide form?
Alcohols.
What are the conditions of nucleophilic substitution with cyanide?
*warm ethanolic potassium cyanide
*carried out under reflux
What does nucleophilic substitution with cyanide form?
Nitriles.
What are the conditions of nucleophilic substitution with ammonia?
*heat with ethanolic ammonia
*excess ammonia
What does nucleophilic substitution with ammonia form?
Amines (+ammonia ion).
How do you know an amine has been formed?
They smell fishy.
What happens to the reactivity of halogenoalkanes down the group?
Increases.
What determines reactivity?
Bond strength/bond enthalpy.
Why does reactivity of halogenoalkanes increase down the group?
*C–X bond strength/enthalpy decreases
*easier to break
*more reactive
What are the conditions of elimination with hydroxide?
*warm ethanolic sodium hydroxide
*carried out under reflux
What does elimination with hydroxide from?
Alkenes.
How can you tell the reaction is substitution?
*aqueous sodium hydroxide
*solvent is water
*hydroxide ions acts as nucleophile
*forms alcohol
How can you tell the reactions is elimination?
*ethanolic sodium hydroxide
*solvent is ethanol
*hydroxide ion acts as base
*forms alkene
What is a base?
A proton acceptor.
What happens if a mixture of water and ethanol as the solvent is used?
Both substitution and elimination occur, forming both alkenes and alcohols.
What are the equations of chlorine radicals depleting the ozone?
*Cl° + O3 → O2 + ClO°
*ClO° + O3 → 2O2 + Cl°
What does chlorine act as in ozone depletions?
A catalyst.
Why is the C–Cl bond broken in the CFC?
It is weaker than the C–F bond.
What is the overall reaction of ozone depletions?
2O3 → 2O2
Why is ozone good?
It absorbs the harmful UV radiation.
What is used now instead of CFCs?
HFCs (contain no chlorine).
Draw the mechanism of bromoethane with a aqueous sodium hydroxide.
Draw the mechanism of bromoethane with ammonia.
Draw the mechanism of bromoethane with a cyanide ion.
Draw the mechanism of bromopropane with ethanolic sodium hydroxide.
