Expt 2 Free Radical Halogenation

Reading Assignment - Lab Manual # 16, pp 127-132. Mohrig Technique 17.4c (pp 214-215).

Experimental Procedures

We will use the procedures as described in the lab manual, except for in part B we will use proton NMR instead of GC to determine the product ratio. Thus, the crude product after alumina filtration is transferred to an NMR tube, CDCl₃ added, and the proton NMR obtained.

Spectrum Analysis

After integrating the spectrum, you need to identify as many peaks as possible and pick out one that can be integrated to represent the relative amount of the 1-chloro product and another one to represent the 2-chloro product. Use the integration values of these peaks to determine the product ratio. (Remember that each integration value needs to be corrected for the number of hydrogens it represents.)

Assigned Questions for Lab Report.

Assigned questions are #3 and #6 in the lab manual and the following:

• An alternative mechanism to that written in the lab manual for chlorination using sulfuryl chloride involves the SO₂Cl radical breaking down to SO₂ and chlorine atoms (Cl∙), which then go on to abstract H from the alkane. Write out this alternative mechanism as well as the book mechanism in the background section of your report.
• It has been reported widely (based on the results of chlorination reactions using Cl₂ and light) that tertiary hydrogens are approximately five times more reactive (k_rel = 5.0) than primary hydrogens (k_rel = 1.0) in their reaction with chlorine atoms. Use this data to calculate the product ratio predicted for our experiment by the alternative mechanism detailed above.
• Use the product ratio as measured by NMR to reach a conclusion regarding the actual mechanism for chlorination using sulfuryl chloride.