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Dehydration and Gas Chromatography of Methylcyclohexanols.

Extracts from this document...

Introduction

Hurst

Chase A. Hurst

CHM 215 11

Dr. Daniel Ketcha

October 28, 2004

Dehydration and Gas Chromatography of Methylcyclohexanols

Introduction

The experimental confirmation of the “Evelyn Effect” was performed in this report.  This effect, first described by David Todd of Pomona College in 1994, describes the formation of 1-methylcyclohexene and 3-Methylcyclohexene (structures shown below) derived from the dehydration and distillation of a mixture of cis-2-methylcyclohexanol and trans-2-methylcyclohexanol (structures shown below) when reacted with phosphoric acid.  

Figure 1.  Stereochemical Structures of Methylcyclohexanols.

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This reaction was carried out according to the following mechanisms.

Figure 2.  Reaction Mechanism of Dehydration of cis/trans-2-methcylohexanol Mixture.

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Procedure

150 mmol (≈ 18.419 g) of 2-methylcyclohexanol (cis - trans mixture) was placed into a 50 mL round bottom flask.  Mixed in this flask was 5 mL of 85% phosphoric acid, 3 drops of sulfuric acid (to quicken reaction), and a few acid resistant boiling chips.  A simple apparatus for distillation was assembled and two 10 mL graduated cylinders were used to collect the distillate.

The contents of the 50 mL round bottom flask were gently brought to a boil and the temperature of the vapor was approximately 115 °C.

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Middle

Figure 3.  Organic Distillate Gas Chromatograms*.

Organic Distillate Sample 1

Organic Distillate Sample 2

image12.jpgimage00.png

image00.pngimage13.jpg

*Arrow indicates 1-methylcyclohexene calculated from standard gas chromatograph of pure 1-methylcyclohexene with retention time of 2.6 minutes.

Table 2.  Organic Distillate Gas Chromatograph Calculations.

Organic Distillate Sample 1 Area and Retention Time Calculations

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Organic Distillate Sample 1 Total Area

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% Composition of Constituents in Organic Distillate Sample 1

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Organic Distillate Sample 2 Area and Retention Time Calculations

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Organic Distillate Sample 2 Total Area

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% Composition of Constituents in Organic Distillate Sample 2

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Table 3.

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Conclusion

Even accounting for this error, however, it seems unlikely that this jeopardized the validity of the experimental results.  While the product yields were significantly lower than those predicted by Todd the results were significant enough in order to see the appearance of the “Evelyn Effect.”  

Furthermore examining the physical/chemical properties of both 1-methylcyclohexene and 3-methylcyclohexene it is apparent that 1-methylcyclohexene is slightly more stable than 3-methylcyclohexene.  This property can be deduced by examining the boiling points of the two isomers.  The boiling point of 1-methylcyclohexene is 110 °C while the boiling point of 3-methylcyclohexene is slightly lower at 104 °C.  The slightly larger amount of heat energy required to boil 1-methcycyclohexene (6 °C) than 3-methylcyclohexene shows that the latter is slightly more stable.  In this context it becomes apparent that 3-methylcyclohexene is more apt to convert to 1-methylcyclohexene; the more stable of the two isomers.  



[1] Density given in g/mL

a Mixture of cis/trans isomers

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