Free radical substitution Flashcards
What happens during free radical substitution?
hydrogen atoms on alkanes/halogenoalkanes are replaced by halogen atoms
what happens on overall equation?
for every hydrogen replaces, one molecule of halogen is used and one molecule of hydrogen halide is released
how would you replace lots of hydrogen atoms?
use an excess of halogen atoms
how would you only replace one hydrogen atom?
use an excess of alkane
what are three stages of free radical substitution?
1) initiation
2) propagation
3) termination
what happens during initiation?
a halogen splits into two halogen free radicals under presence of UV light
what happens during propagation?
- production of more free radicals
for every hydrogen atom replaces, a pair of propagation reactions occur
what happens during step 1 of propagation reactions?
- alkane and halogen free radical reacts
- removes one hydrogen atom from alkane and produces a carbon based free radical
- also produces hydrogen halide
what happens during step 2 of propagation reactions?
- carbon based free radical reacts with halogen atom
- adds one halogen atom onto carbon based radical
- also produces a halogen free radical
why is another halogen free radical produced during step 2 of propagation reaction?
to continue chain reaction of producing free radicals
what happens during termination stage?
two free radicals collide to form a molecule and stops chain reaction
what are free radicals?
species with odd number of electrons
