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Purpose: To determine the major product in the acid-catalyzed dehydration of methycyclohexanols using GC analysis, demonstrating Zaitsev's rule.
Purpose: To determine the major product in the acid-catalyzed dehydration of methycyclohexanols using GC analysis, demonstrating Zaitsev's rule.
CHOOSE which reaction below to 'perform'
CHOOSE which reaction below to 'perform'
dehydration of 1-methylcyclohexanol OR 2-methylcyclohexanol
dehydration of 1-methylcyclohexanol OR 2-methylcyclohexanol
1-methylcyclohexanol
2-methylcyclohexanol
E1 Reaction Mechanisms
E1 Reaction Mechanisms
E1 = Unimolecular elimination, occurs in two steps, favored with weak bases (ex. water)
Dehydration of 1-methylcyclohexanol
Dehydration of 1-methylcyclohexanol
Dehydration of 2-methylcyclohexanol
Dehydration of 2-methylcyclohexanol
Both reactions above have the same major product: 1-methylcyclohexene.
This can be predicted by Zaitsev's rule.
Hold on a sec, who's this Zaitsev guy and how did he get his own rule?
Hold on a sec, who's this Zaitsev guy and how did he get his own rule?
Klein, Organic Chemistry, 3rd ed. Figure 7.13
Zaitsev's Rule
Zaitsev's Rule
More highly substituted alkenes are more stable
Substitution patterns are determined by the number of carbon atoms (highlighted in green) directly attached to the alkene C's
Many many elimination reactions were carried out with a small base, each consistently favoring the more highly substituted alkene.
Are there exceptions to Zaitsev's Rule?
Are there exceptions to Zaitsev's Rule?
You betcha! We don't see those exceptions in this lab, but for your curiosity...
The size of the base can play a role, but only in E2 reactions
E2 = bimolecular substitution, occurs in one step
E2 mechanism occurs with strong base
Smaller bases form more substituted alkenes (Zaitsev product)
Larger bases form less substituted alkenes (Hofmann product)
Learning Objectives
Learning Objectives
Observe microscale distillation apparatus to collect products of a dehydration reaction
Use gas chromatography (GC) to determine percent composition of products, exemplifying Zaitsev’s rule
Apply IR Spectroscopy to determine reaction success
Interpret permanganate tests to determine presence or absence of alkene
Recommended Background Reading on Organic Reactions
Recommended Background Reading on Organic Reactions
Chapter Sections in McMurry, Organic Chemistry, 8th ed. or Klein, Organic Chemistry, 3rd ed.
Elimination Reactions: McMurry 11.7-11.10 or Klein 7.1, 7.6 – 7.7, 7.9, 7.11
Dehydration of Alcohols: McMurry 17.6 or Klein - 12.9
Oxidative Cleavage of Alkenes: McMurry - 7.9 Klein - 8.12, Klein text doesn’t specifically cover oxidative cleavage with KMnO4
How to do this remote lab
How to do this remote lab
On the pages that follow, read the captions, check out the photos, and watch videos
There is no sound on videos, aside from background music, for accessibility reasons
Click the pink button(s) at the bottom of each page to move on to the next step
Feel free to make mistakes
Click on the 'Home' menu on the top right to jump back or forward to main parts of the lab
Record observations and data
TAs provide starting volume - or students use this random number generator to get a unique 'starting volume' (725 - 775 uL)
Recalculate the theoretical yield of methylcyclohexene (mg) from your unique 'starting volume'
Remote lab purposes only:
This theoretical yield is your maximum product yield, from which you'll subtract 'product loss'
Keep track of product loss, given throughout the procedure this series of websites, and add them up to include a "total product loss" in your notebook
Calculate your 'actual yield' = (theoretical yield) - (total product loss)
Calculate the percent yield = [(actual yield) / (theoretical yield)] x 100%
Recall your starting alcohol (1-methyl or 2-methyl) to gather appropriate reaction results...
Record observations from chemical tests
Analyze the IR spectra of the starting material and products
Note: 1-methyl- and 2-methylcyclohexanol have the same IR spectrum, so only one is provided :)
Calculate the retention times of GC standards, then select your alcohol to get the GC results for your reaction.
Calculate the retention times and area of sample peaks, then calculate the percent composition.
"Clean Up" then review any parts of the experiment you like :)
Assessment components - to-do list
Assessment components - to-do list
Exp 5 Pre-lab quiz - take on Canvas before lab
Prepare your notebook per the Exp 5 Lab Notebook Templates on Canvas
After 'performing' this remote lab and gathering data, upload your Exp 5 Lab Notebook pages to Canvas
Complete the Exp 5 Lab Report (abstract and in-lab questions) per instructions on the last page of the Exp 5 document
You have the OPTION to work on this lab with ONE partner and submit the lab report to GradeScope together
one student uploads, select "add Group Member" - MAX group of TWO
It is 100% OK to complete this report individually
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