haloalkanes Flashcards
what are haloalkanes
compounds containing carbon hydrogen and at least one halogen
are haloalkanes soluble in water and why
They are insoluble as C-H bonds are non polar and not compensated for enough by C-X polarity
do haloalkanes have a polar bond and explain why
Yes halogen has a higher electronegativity than carbon so the electrons in the bond are attracted towards halogen making the bond polar
What are nucleophiles
Electron pair donors
What intermolecular forces do haloalkanes form
London forces and permanent dipoles C-X
Explain the trend in boiling point as carbon chain length increases of haloalkanes
Higher boiling point as carbon chain increases and halogen higher group 7 so C-Cl has the highest bond enthalpy and C-I is the most reactive
What is nucleophilic substitution
When a haloalkane reacts with a nucleophile and it replaces the halogen
What happens during hydrolysis of a haloalkane
The halogen atom is replaced by an OH group, the C-X Bond is broken by heterolytic fission Producing an alcohol and a halide ion
What are cfc’s
Chlorine fluoro carbons
What is the problem with Cfc’s
Although they have a low boiling point so low reactivity and non toxic under normal conditions they catalyse the breakdown of ozone in the atmosphere via free radical substitution
The ozone layer provides protection from harmful uv radiation that causes skin cancer
Measuring rate of hydrolysis of primary haloalkanes
> Ionic equation – Ag+ + X- -> AgX(s)
Set up the three test tubes in a water bath of 60 containing ethanol and chloro bromo iodo, And an additional one of silver nitrate. After they reach a constant temp add 1cm3 of AgNO3 and start a timer.
- Iodo reacts fastest forming a yellow precipitate
- Then Bromo forming a cream precipitate
- Chloro reacts slowest forming a white precipitate
What can we conclude from the rate of hydrolysis experiment
Rate of hydrolysis increases as strength of carbon-halogen bond decreases
What is photo dissociation
CFCs forming radicals
CF2Cl2 -> CF2Cl. + Cl.
How does the chlorine radical breakdown the ozone layer into oxygen include all three steps
Cl. + O3 -> ClO. + O2
ClO. + O -> Cl. + O2
overall - O3 + O -> 2O2
Nitrogen oxide radicals formed during lightning strikes or as a result of aircraft travel also catalyse the breakdown of ozone show all three steps of the reaction
NO. + O3 -> NO2. + O2
NO2. + O -> NO. + O2
overall - O3 + O -> 2O2
Show the reaction for the formation and broke down of ozone
O2 -> 2O
O2 + O <-> O3
List three sources of CFCs in the atmosphere
Refrigerants, air-conditioning units and aerosol sprays
State two sources of nitrogen oxides in the stratosphere
Thunderstorms / lightning AND aircraft
What are the layers of the atmosphere?
Troposphere stratosphere ozone
How does HCCIF2 breakdown to form two radicals?
HCF2. + Cl.
Write an equation for the formation of C4H10O2 from C4H8Cl
C4H8Cl + 2OH- -> C4H10O2 + 2Cl-
