Experiment 5
13
Experiment 5
Lab Report
How Can a Complex
Alkene be Synthesized?
R Br
?
R Mg Br
?
H
R' O
?
This is an individual report.
Title Page: (See Lab Manual Part III. p. 19)
The Questions of the Week:
State the Questions of the Week:
Weeks 1 & 2: How can a Grignard Reaction be Successfully Accomplished?
Consists of the Retrosynthetic analysis for the synthesis of 2-methyl-2-heptene, the synthesis developed
from it and a picture of the apparatus used for the Grignard reaction with the parts of the set up designed to help
exclude moisture labeled. (All of these can be drawn by hand or using ChemDraw).
Week 3 & 4:
What is the Outcome of the Dehydration of an Alcohol?
Present the structures and names of the proposed alkene products from our discussion of the likely mechanism.
Again structures can be drawn by hand or using ChemDraw.
Summary of Results: (See Lab Manual Part III. p. 20)
Data only:
A GC Analysis Table showing retention times for standards and the product component data from analysis of
your product mixture. Include yields and overall % yields for all three alkene products detected in the GC
analysis. (See MSWord form linked to the Experiment 5 page of the course website.)
A Yield Table showing (See Excel form linked to the Experiment 5 page of the course website.):
 The identity, mass and moles of the limiting reagent for the total synthesis.
 The theoretical yield (mass and moles) for each step of the synthesis.
 The mass and moles of 2-methyl-3-heptanol obtained and the % yield.
 The mass and moles of total alkenes obtained and the % yield for the dehydration step.
 The mass and moles of 2-methyl-2-heptene obtained and the % yield for the dehydration step.
 Overall % yield of total alkenes for all three steps of the synthesis.
 Overall % yield of 2-methyl-2-heptene for all three steps of the synthesis.
Discussion and Conclusions: (See Lab Manual Part III. p. 20)
1. What evidence do you have that you synthesized and isolated the target alkene?
2. The dehydration of 2-methyl-3-heptanol is an example of an acid-catalyzed E1 reaction whose mechanism
we discussed in class. You learned that these reactions proceed through a carbocation intermediate to give
predominantly the lowest energy alkene. Is the class experimental data consistent with our classroom
analysis? Explain why or why not?
3. Your retrosynthetic analysis was focused on the synthesis of 2-methyl-2-heptene; however, it led to the
isolation of a mixture containing 3 major alkenes. Use the expected E1 mechanism to explain how 3
different 2-methylheptenes could have been formed from this dehydration reaction.
4. What insights about the synthesis of organic compounds in general or alkenes in particular have you gained
from your experience in the multistep synthesis of 2-methyl-2-heptene?
Appendix: (See Lab Manual Part III. p. 24)
Include all items in the Experiment 5 section of your Data Binder.
Laboratory Report Due Date:
CHEM 212 Experiment 4
14
Alkene Synthesis
Your lab report for Experiment 5 is due by the end of your lab period during the last week of the semester (April
28-30, 2009). Notebooks and data binders are due at the final exam: 8:30 AM Tuesday May 5.