alkanes

Question 1

what are alkanes?

Answer 1

saturated hydrocarbons containing single bonds as well as pi bonds with free rotation

Question 2

why do alkanes form tetrahedral shapes?

Answer 2

the four pi bond pairs around each carbon repel equally to make a bond angle of 109.5

Question 3

how and why does the BP in alkanes change with chain length?

Answer 3

1. it increases with chain length
2. stronger London forces in larger molecules
3. more energy required to break them

Question 4

why (by and large) do alkanes have a low reactivity?

Answer 4

high bond enthalpy and low polarity of pi bonds

Question 5

what is the formula for balancing combustion equations

Answer 5

0.5 x hydrogen; balance carbons and 0.5 x oxygen

Question 6

what are the dangers of incomplete combustion of alkanes?

Answer 6

carbon monoxide poisoning and pollution

Question 7

what are the industrial and commercial uses of alkanes?

Answer 7

combustion as fuel

Question 8

can you describe the radical substitution of alkanes?

Answer 8

Initiation - homolytic fission of bromine to form br radicals in UV
propagation - radicals react and form other radicals
termination - two radicals form a stable product

Question 9

what are the limitations of radical substitution in synthesis?

Answer 9

1. further substitutions can occur, forming other haloalkanes
2. difficult to control