chloralkanes and CFCs
- Created by: Margaret Hobart
- Created on: 13-05-21 17:24
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- chloroalkanes and CFCs
- chlorination of alkanes
- free radicals are particles with unpaired e-
- formed when a covalent bond splits equally, giving one e- to each atom
- unpaired e- makes them reactive
- homolytic fission
- covalent bond breaks and both of the bonded atoms take one e- form bond
- it's now a free radical
- covalent bond breaks and both of the bonded atoms take one e- form bond
- heterolytic fission
- covalent bond breaks and one of the bonded atoms takes both of the e- from the bonds
- the atom that takes both is a (-) ion and the atom that loses is a (+) ion
- e.g. H3C-Cl-> H3C+ + Cl-
- covalent bond breaks and one of the bonded atoms takes both of the e- from the bonds
- Halogens react with alkanes in photochemical reactions
- UV radiation provides energy for initiation
- free radical substitution
- limitations
- in stage 1 you could have more than 1 free radicals colliding with chloromethane, substituting further H atoms
- in longer alkanes you can get a mix of mono-substituted isomers
- limitations
- 1. Initiation 2. Propagation 3. Termination
- initiation: produces free radicals
- propagation: free radicals are used up and created in a chain reaction
- termination: free radicals are used up
- e.g. chlorine and methane
- free radicals are particles with unpaired e-
- Chlorofluorocarbons
- all hydrogens have been replaced by Cl and F
- depletion of ozone
- chlorine free radicals are formed in the atmosphere
- Chlorine atoms catalyse the decomposition of ozone
- holes in ozone layer
- UV light breaks C-Cl bonds in CFCs
- Chlorine atoms catalyse the decomposition of ozone
- Cl?+ O3 -> ClO?+ O2
- ClO?+ O3 -> 2O2 + Cl? Overall: 2O3 ? 3O2
- chlorine free radicals are formed in the atmosphere
- chlorination of alkanes
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