Taylor Collins
“Dehydration of Methylcyclohexanols”
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Pre-lab and Observations
: Attached
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Results
:
Flask 1:
5.15 grams
Flask 2:
3.85 grams
Total:
9.00 grams
Percent Yield:
(9.00/17.13)*100=
52.5%
Balanced Reaction:
GC analysis:
4-methylcyclohexene was 80.8% of the product in the first fraction and 78.6% in
the second fraction.
The first fraction was comprised of 4.6% cis-4-methylcyclohexanol
and 10.8% trans-4-methylcyclohexanol.
The second fraction was comprised of .63% cis-
4-methylcyclohexanol and 6.3% trans-4-methylcyclohexanol.
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Discussion
:
The purpose of this experiment was to carry out the dehydration of 4-
methylcyclohexanol by heating the alcohol in the presence of phosphoric acid.
The
alcohol was a mixture of cis and trans isomers so it could exhibit the Evelyn effect which
was one of the main objectives to discover.
By protonating an alcohol, the acid catalyst
converts the poor leaving group—OH to a much better leaving group—+H2O.
Elimination of H+ and H2O from the protonated alcohol yields an alkene, with the
unprotonated alcohol serving as the reaction solvent. Markovnikov’s rule states that when
HZ adds to the carbon-carbon double bond of an unsymmetrical alkene, hydrogen adds
preferentially to the carbon atom that already has more hydrogens.
However, Zaitzev’s
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- Spring '08
- Staff
- Reaction, final product, Organic reaction, Phosphoric acid, trans isomers
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