Chem 334 - Fall 1998 - Organic Chemistry
I 1. (3 points) Using the table of bond dissociation energies
in Appendix 3, calculate delta H for each of the following reactions.
Clearly identify the bonds made and the bonds broken for each
reaction.
a) CH3CH3 + Cl2 -> CH3CH2Cl + HCl
delta H = +100 + 59 - 80 - 103 = -24
b) CH3CH3 + Br2 -> CH3CH2Br + HBr
delta H = +100 + 46 - 68 - 88 = -10
c) CH3CH2CH3 + Cl2 -> (CH3)2CHCl + HCl
delta H = +96 + 59 - 81 - 103 = -29
d) CH3CH2CH3 + Br2 -> (CH3)2CHBr + HBr
delta H = +96 + 46 - 68 - 88 = -14
e) (CH3)3CH + Cl2 -> (CH3)3CCl + HCl
delta H = +93 + 59 - 79 - 103 = -30
f) (CH3)3CH + Br2 -> (CH3)3CBr + HBr
delta H = +93 + 46 - 68 - 88 = -17
2. (2 points) Write a chain reaction mechanism for the reaction below. Show all steps.
H2 + Cl2 -> 2 HCl
initiation:
Cl2 --> 2 Cl.
propagation:
Cl. + H2 --> HCl + H.
H. + Cl2 --> HCl + Cl.
termination:
2 Cl. --> Cl2
2 H. --> H2
H. + Cl. --> HCl