Dehydration of Methylcyclohexanol

Abstract

In this experiment, the dehydration of 2-methylcyclohexanol and 4-methylcyclohexanol was carried out by heating the alcohols in the presence of phosphoric acid. Both alcohols were mixtures of cis and trans isomers, so either one or both may exhibit an Evelyn Effect.

Introduction

The purpose of this experiment was examining the Evelyn Effect by carrying out the dehydration of 2-methylcyclohexanol and 4-methylcyclohexanol and heating the mixture of the alcohols and the phosphoric acid. Alcohol and the alkene can be separated by using their boiling point differences

These are the chemicals that used in the experiment.

Molecular W. Boiling point Density

2-methylcyclohexanol 114.2 166 0.930

4-methylcyclohexanol 114.2 173 0.914

1-methylcyclohexene 96.2 110 0.813

3-methylcyclohexene 96.2 104 0.801

4-methylcyclohexene 96.2 102 0.799

Phosphoric acid (85%) 98.0 158 1.70

The mechanism of the 2-methlycyclohexanol:

Procedure

A 20 mmol of 2-methylcyclohexane was weighed and put into a 1* mL round-bottom flask. It was mixed with 0.70 mL 85% phosphoric acid and the mixture was put into a stir bar. It was clamped to a stable place. The reactants were heated in stirrer until they started to be distillated. The temperature was recorded at that moment. After the distillation had completed the product was separated two parts. Each one was 1 mL. Each one was washed with 1.5 mL of 5% sodium bicarbonate. The lower layer was separated by using Pasteur pipet. Each mixture was dried with anhydrous calcium chloride. The total mass of alkenes was measured and recorded. Using gas chromatography both fractions were analyzed.

Results and Discussion

The volume of 2-methylcyclohexanol: Volume of 2-methylcyclohexanol=20.0mmol×(〖10〗^(-3) mol)/1mmol×114.2gram/(1 mol)×1mL/(0.930 gram)≈2.46mL

The following table showed the measured mass in the experiment:

The mass of the vial (g) The total mass (g)

First vial 16.0297 16.3919

Second vial 16.1790 16.3893

According to the mass showed above,

The mass of the alkene in the first vial=16.3919 gram-16.0297 gram=0.3622