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Iodination of alkanes using iodine (I2) is usually an
Chapter 5, Problem 57SP(choose chapter or problem)
Iodination of alkanes using iodine \(\left(\mathrm{I}_{2}\right)\) is usually an unfavorable reaction. (See Problem 4-17, for example.) Tetraiodomethane \(\left(\mathrm{Cl}_{4}\right)\) can be used as the iodine source for iodination, in the presence of a free-radical initiator such as hydrogen peroxide. Propose a mechanism (involving mildly exothermic propagation steps) for the following proposed reaction. Calculate the value of \(\Delta H\) for each of the steps in your proposed mechanism.
Equation Transcription:
Text Transcription:
(I2)
(Cl4)
\Delta H
CI4
H2O2
HCI3
I3C-I
HO-I
Questions & Answers
QUESTION:
Iodination of alkanes using iodine \(\left(\mathrm{I}_{2}\right)\) is usually an unfavorable reaction. (See Problem 4-17, for example.) Tetraiodomethane \(\left(\mathrm{Cl}_{4}\right)\) can be used as the iodine source for iodination, in the presence of a free-radical initiator such as hydrogen peroxide. Propose a mechanism (involving mildly exothermic propagation steps) for the following proposed reaction. Calculate the value of \(\Delta H\) for each of the steps in your proposed mechanism.
Equation Transcription:
Text Transcription:
(I2)
(Cl4)
\Delta H
CI4
H2O2
HCI3
I3C-I
HO-I
ANSWER:
Solution 57SP
Here, we are going to calculate the value of for each of the steps in your proposed mechanism.
Step 1:
Mechanism
Here, Bond dissociation energy of bonds broken :
HO-OH = 213 kJ/mol
I-CI3 = 188 kJ/mol
Bond dissociation energy for bonds formed :
HO-I = 234 kJ/mol
o = [Bond dissociation energy for bonds broken] -[Bond dissociation energy for bonds formed]
= +188 kJ/mol - 234 kJ/mol = -46.0 kJ/mol