Reaction mechanisms

Question 1

Three steps in a radical chain reaction

Answer 1

Initiation - uv light causes homolytic fission forming 2 free radicals

Propagation - a radical reacts but another radical is produced so continuing the chain

Termination - when the radicals are removed from the reaction (by reacting with each other)

Question 2

Homolytic Fission

Answer 2

Occurs when the bond is not polar or only slightly polar. Electrons are shared evenly between both atoms so forms two electrically neutral, highly reactive free radicals.

Question 3

Heterolytic

Answer 3

Occurs when the bond is polar. One atom gets both electrons from the bond so an ion pair is formed (the slightly negative end will keep both electrons).

Question 4

Electrophiles

Answer 4

Electron loving so will have a positive charge or polarity which causes a slight positive charge. Will react with nucleophiles

Question 5

Nucleophiles

Answer 5

Nucleus loving so must be negatively charged or have at least on lone pair of electrons. Seeks out electron deficient areas to react with and form new bonds

Question 6

SN1

Answer 6

A two step nucleophillic substitution via a relatively stable carbocation (overall positive). This is then subject to nucleophillic attack. The initial creation of the intermediate is the rate determining step and the 1 in SN1 indicates that there is only one species involved,
In haloalkanes most likely to occur with tertiary as the carbocation will be more stable.

Question 7

SN2

Answer 7

A one step nucleophillic substitution where a five centred, overall negative, transition state is formed. The two stands for two species in the rate determining step.
In haloalkanes more likely to occur with primary.