Organic Chemistry Laboratory I - Chem 341

Quiz 9a

1. How might the ratio of alkenes obtained in the tert-butoxide-promoted elimination reaction change if the tert-butyl alcohol contains water? (2 pts)

Any water might react with the t-BuOK to form t-butanol and KOH. The presence of KOH would favor elimination to form 2-methyl-2-butene. Thus, the ratio of the two products would change, in this case reducing the amount of 2-methyl-1-butene formed.

2. Circle the major organic product from the following reaction. (2 pts)

3. Sketch the ¹H NMR spectrum for the following compound; label the peaks with corresponding protons and include the relative integration numbers for each signal. (3 pts)

1/2 pt for correct number of peaks, splitting patterns, integration number, and chemical shift

4. Circle the structure most consistent with the following ¹H NMR spectrum. (2 pts)

5. Why does excess of base used in the elimination reactions favor the E2 over the E1 mechanism? (2 pts)

The E2 elimination is kinetically second-order and is affected by the base and alkyl halide concentration; thus, it is accelerated by an increase in base concentration. However, the E1 reaction, is first-order and the rate only depends on the concentration of alkyl halide; thus, increasing the base concentration has little effect on the rate for the E1 mechanism.