Distillation and Strong C-h Stretch

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Lab #24-
Preparation 4-Methylcyclohexene

The goals in this lab were to have a reaction occur with 4-methylcyclohexanol and an acid catalyst to form our product of 4-methylcyclohexene via an E1 reaction. This reaction is accomplished by removing the –OH group on 4-methylcyclohexanol via dehydration and to have a double bond form via a loss of a hydrogen on a β-Carbon.

Many techniques and skills were developed in this lab. Among them were dehydration, isolation, drying, and distillation. We used all of these techniques to get the product we were looking for. In addition to these experimental techniques we also verified our product via spectroscopy which is a new technique. Using IR spectroscopy we were able to specifically analyze the functional groups on our product.

Results and Discussions:

Reaction Equation:
Theoretical Yields: Based on limiting moles of product
-Based on C7H14O
24 mL C7H14O x (0.910 g C7H14O/1 mL C7H14O) x
(1 mol C7H14O/114.19 g C7H14O) = 0.191 mol C7H14O
0.191 mol C7H14O x (1 mol C7H12/1 mol C7H14O) = 0.191 mol C7H12 C7H14O is the Limiting Reagent
-The acids are not counted as reagents in this reaction and serve only as catalyst.

Theoretical Yield = mol of limiting reagent x M.W.
= 0.191 mol x 96.17 C7H12 = 18.39 g C7H12

Actual Yield: 10.27 g C7H12

Percent Yield: (Actual/Theoretical) x 100%
= (10.27/18.39) x 100%
= 55.83 %

Analytical Data:
-Boiling Point: The liquid had a boiling point between 101°C and 102 °C. According to Paula, Lampman, Kriz, and Engel, Introduction to Organic Techniques, 2004 3rd Ed. Experiment 24: Preparation of 4-Methylcyclohexene, pg 193 the boiling point of the compound should be between 100 and 105 °C. Our value is very close indicating a pretty pure substance. Impurities in the desired substance can alter the boiling point. - Looking at the liquid once distilled, the product was nearly completely clear with some cloudiness which was a good indication that our distillation removed nearly all the impurities that were in the solution prior to distillation leaving almost only our desired product in the bulb. - Br2 Test- Solution remained clear after the addition of multiple drops of Br2 indicating the electrophilic addition reaction to 4-methylcyclohexene. - KMnO4 Test- Solution turned brown after adding KMnO4 indicating a double bond in the ring prior to KMnO4 addition meaning we started with 4-methylcyclohexene.

- IR Spectroscopy

|Absorbance (cm-1) |Shape |Intensity |Group-Motion | |3024 |Sharp |Strong |C-H Stretch (Alkene) | |2921 |Sharp |Strong |C-H Stretch (Alkane) | |2825 |Sharp |Strong |C-H Stretch (Alkane) | |1657 |Sharp |Medium |C=C Stretch | |1444 |Sharp |Medium to Strong |C-H Bending (Alkane) | |1368 |Sharp |Medium |C-H Bending (Alkane) |

Side Reactions:

Procedure: Followed the procedure verbatim found in the lab manual- Pavia, Lampman, Kriz, and Engel, Introduction to Organic Lab Techniques 2004, 3rd Ed. Experiment 24: Preparation of 4-Methylcyclohexene, pg 193-197. -No special observations or non-ordinary results appeared. Everything went just as expected.

Summary: Reaction and flow diagram for preparation and isolation of...
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