Halogenoalkanes Flashcards
(37 cards)
What is the general formula of the homologous series of halogenoalkanes?
CnH2n+1X
Why is the C-X bond polar?
Bc the halogen atom is more electronegative than the C atom
Why do C-X bonds become less polar as you go down the group?
Halogens become less electronegative as you go down the group
What intermolecular forces are present in halogenoalkanes?
van der Waals forces and permanent dipole dipole interactions
Why does boiling point increase as chain length of the halogenoalkanes increase?
Greater Mr so greater van der Waals forces between the molecules
Why does the boiling point increase as the halogen used goes down the group?
Greater Mr so greater van der Waals forces between the molecules
Are halogenoalkanes soluble in water?
No
What are halogenoalkanes soluble in?
Organic solvents
Why is free radical substitution a photochemical reaction?
Bc it’s brought about by light
What is a free radical?
An atom or a group with an unpaired electron
What is homolytic fission?
When a bond breaks equally
Why is free radical substitution a chain reaction?
For every reactive species you start off with, a new one is generated
What does free radical substitution do?
Forms halogenoalkanes
Explain the process of free radical substitution
Initiation - free radicals made by homolytic fission caused by UV light
Propagation - free radicals act as catalyst to form halogenoalkanes
Termination - the chain reaction is terminated bc free radicals come together to make non-free radicals
What is ozone?
It’s an allotrope of oxygen found in the ozone layer of the stratosphere
Why is ozone useful?
Absorbs UV light from the Sun
Why is UV light dangerous?
Can cause sunburn, cataracts in the eye, skin cancer, damage to plant tissue and reduce plankton populations in the ocean
Why is ozone depleting?
Halogen free radicals such as CFCs
What are CFCs used in?
Aerosols, solvents, coolants in refrigerators bc non-toxic and non-flammable
Why are CFCs dangerous?
Released into the lower atmosphere where they do not degrade they diffuse into the stratosphere where they’re made into free radicals and then cause ozone to deplete
What solutions have governments made to stop ozone depletion?
200 countries have signed the Montreal Protocol which pledges to wipe out ozone-depleting agents
Chlorine-free compounds being used like hydrofluorocarbons
What are primary halogenoalkanes?
2 hydrogens attached to the carbon with the halogen
What are secondary halogenoalkanes?
1 hydrogen attached to the carbon with the halogen
What are tertiary halogenoalkanes?
0 hydrogens attached to the carbon with the halogen
