1. In addition to your own group's results, also report the GC-MS results for both labs given above.
2. The Wednesday reactions gave the desired mono-bromo product but also gave greater amounts of dibromocyclohexenes. (Identify the GC peaks for the desired product and the dibromo products on the basis of the retention times and mass spectra.) The Thursday reactions gave the desired mono-bromo as the major product with little to no evidence for dibromocyclohexene formation. Explain why Wednesday gave lots of dibromo products whereas Thursday gave none.
3. Three different isomers of dibromocyclohexene show up in the GC-MS of the Wed reactions. Use the mechanism and resonance theory to deduce which isomers these are most likely to be.
4. The peak at 9:25 min in the Thursday reaction GC-MS shows M at 242 (with the 1:2:1 isotope pattern expected for two Brs) and M - Br at 161, 163, consistent with it being dibromocyclohexane. Which isomer of dibromocyclohexane is this most likely to be and how does it form?
5. Do the NMR spectra show evidence of the presence of benzoyl peroxide in the crude product? Identify peaks due to this compound.
6. Propose a mechanism for the reaction of NBS with HBr (eq 2) showing curved arrows. Hint: this is a two-step mechanism that starts with a proton transfer step.