3. reactions of alkanes

Question 1

breaking a covalent bond is called

Answer 1

bond fission

Question 2

heterolytic fission

Answer 2

bond breaks unevenly
1 bonded atom receives both electrons from bonded pair
positively charged cation X+
negatively charged anion Y-

Question 3

homolytic fission

Answer 3

bond breaks evenly
each bonding atom receives one electron from bonded pair
2 electrically uncharged radicals formed

Question 4

radicals are

Answer 4

particles that have an unpaired electron

shown in mechanisms with big dot next to molecular formula

Question 5

why are radicals very reactive

Answer 5

because of the unpaired electron

Question 6

what does a curly arrow show

Answer 6

the movement of an electron pair

Question 7

halogens can react with alkanes in what kind of reaction

Answer 7

photochemical reaction (started by light)

Question 8

what starts reaction between haloalkanes and alkanes

Answer 8

UV light

Question 9

free radical substitution

3 main stages

Answer 9

initiation reaction- free radicals produced
propagation reaction - free radicals used up and created in chain reaction
termination reaction - free radicals mopped up

Question 10

problem with free radical substitution

Answer 10

mixture of products (have to separate desired products from unwanted products)
can take place at any point along C chain = mixture of isomers

Question 11

how to reduce the chance of mixture of byproducts in radical substitution

Answer 11

excess of methane - greater chance of chlorine radical only colliding with methane not chloromethane