Chapter 12

Question 1

what covalent bonds are found in an alkane?

Answer 1

sigma bonds

Question 2

what is a sigma bond?

Answer 2

a direct overlap of the s orbitals

Question 3

what is the bond angle in all alkanes?

Answer 3

109.5 degrees

Question 4

effect of increasing chain length on boiling point

Answer 4

increasing carbon chain length increases the surface area
means more contact points for London forces
more London forces mean a stronger attraction between molecules which require more energy to overcome

HIGHER BP

Question 5

effect of increased branching on boiling point

Answer 5

increased branching means fewer contact points for London forces
fewer London forces means weaker attraction which requires less energy to overcome

LOWER BP

Question 6

why is there a lack of reactivity in alkanes?

Answer 6

the C-C and C-H bonds are strong
alkanes are all non-polar

Question 7

what is the mechanism by which alkanes react with halogens?

Answer 7

radical substitution

Question 8

what are the three stages of radical substitution?

Answer 8

initiation
propagation
termination

Question 9

what are the two limitations of radical substitution?

Answer 9

further substitution
substitution at different points along the carbon chain

Question 10

substitution at different points along the carbon chain

Answer 10

RS will produce a mixture of mono-substituted haloalkanes as the halogen can be bonded to any carbon along the carbon chain

Question 11

further substitution

Answer 11

RS can continue to occur as it is a chain reaction which can lead to all hydrogen atoms being substituted