Organic Chemistry: Radical Substitution(Alkanes)

Question 1

what is the condition needed for the radical substitution of alkanes?

Answer 1

ultraviolet light and high temperatures

Question 2

what is the first step of radical substitution?

Answer 2

initiation - radicals are formed from molecules

Question 3

what is the second step of radical substitution?

Answer 3

propagation - radicals react with molecules and a radical is always formed

Question 4

what is the third step of radical substitution?

Answer 4

termination - radicals react together to form molecules

Question 5

what is the general first step (initiation) of radical substitution?

Answer 5

Cl2 –> 2Cl°

Question 6

what is the general second step (propagation) of radical substitution,using ethane?

Answer 6

C2H6 + Cl°–> C2H5° + HCl
C2H5° + Cl2 – > C2H5Cl + Cl°

Question 7

what is the general last step (termination) of radical substitution?

Answer 7

Cl°+ Cl°–> Cl2
C2H5° + C2H5° –> C4H10
C2H5° + Cl° –> C2H5Cl

Question 8

what are the two main problems with radical substitution?

Answer 8

• the halogen can add to the same molecule more than once, further substitution as for example the bromine could add to any hydrogen on the propane molecule
• the halogen can add to more than one position on the molecule, different positions in a carbon chain as for example if you want 1-bromopropane and the bromine adds to the second carbon, this is not what you wanted

Question 9

what type of fission is radical substitution and why?

Answer 9

homolytic fission because each bonding atom receives one electron from the bonded pair, which breaks the covalent bond and forms 2 radicals