Dehydration of 2 Methylcyclohexanol Lab Report

Virtual Lab: Dehydration of 2-methylcyclohexanol

NC State Virtual Lab

Watch the NC State virtual lab https://go.ncsu.edu/vrlab-gc

A couple of the reaction mechanism arrows in the video are not exactly correct. Please use the mechanisms in this document as a guide. You can also view the lab on YouTube with speed and caption options. https://go.ncsu.edu/vrlab-gc-captions You can answer the questions as you follow along.

Introduction: In an E1 reaction, a good leaving group, and a beta-hydrogen are eliminated in a stepwise reaction to form an alkene. The good leaving group may be a weak base such as a halide ion or a neutral molecule such as water. In this experiment, 2-methylcyclohexanol will be heated in the presence of a strong acid, phosphoric acid, to promote the E1 reaction. Phosphoric acid first protonates the alcohol, converting it into a good leaving group (H2O). The water then leaves, forming the carbocation intermediate. In the final step of the mechanism a water molecule acts as a base and removes the beta-hydrogen, forming the alkene. The dehydration mechanism for cyclohexanol is shown below. 

https://lh5.googleusercontent.com/s0LKE6PXdtSTNzN492_mBLk3KCoUzxaLWV3q-NSOXuDh1hkI0YN3sTcC6GkW5OAw7fRtR-VfhG2DbugRRynWjljC6jBPHZdKp5kcbBEp511m3rQU11gsjEguWlH0xntdwLPhFEY

Figure 11.2 Mechanism for the acid catalyzed E1 reaction of cyclohexanol. (From Organic Chemistry by Bruice, 8th Ed.)

Questions

  1. Draw the beta hydrogens on the intermediate. Which hydrogen is more likely to be removed? Explain why. (3 points)
  2. Draw the complete mechanism to form the major product of the reaction. (2 pts)
  3. Draw the mechanism to form the minor product of the reaction. (2 points)

 

  1. How was the product separated/purified from the reaction? (1 point)
  2. What is the purpose of adding sodium sulfate to the reaction product? (1 point)
  3. What type of analysis is used to determine the ratios of the products. (1 point)
  4. What is the approximate retention time for the minor product. (0.5 pt)
  5. What is the approximate retention time for the major product. (0.5 pt)
  6. Draw the structure of the product with the higher boiling point. Explain how you arrived at your answer based on the retention times in the video. (2 points)
  7. Explain how IR could be used to determine if the starting chemical had converted to the product? (1.5 points)
  8. Explain how 1H-NMR could be used to determine if the reaction was successful? Be specific. (1.5 points)
  9. Consider the following dehydration reaction. Propose a mechanism for the reaction to produce the minor product. (2 pts)
  10. Consider the following reaction. Draw the major product and 2 of the minor products. Hint: rearrangement (2 points)
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