Dehydration of an Alcohol: Distillation and Gas Chromatography

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Experiment 2: Dehydration of an Alcohol: Distillation and Gas Chromatography Preparation of Methylcyclohexenes


The basic purpose of this experiment is to carry out the dehydration of an alcohol and isolate the reaction products by distillation. Gas Chromatography will be utilized to analyze the reaction mixture.

Table of Reagents:

Compound (g)Molecular Weight (g/mol)Grams (g)Moles
6 mL of 2-methylcyclohexanol
(C7H14O)114.19 g/mol6 mL x 0.943g = 5.66 g
1 mL5.66 g x 1mol = .0496 mol
114.19 g
5 mL of 85% phosphoric acid
(H3PO4)98.0 g/mol5 mL x 2.01 g = 10.05 g
1 mL10.05 g x 1mol = .1026 mol
98.0 g
Drying Agent Sodium Sulfate
Na2SO4142.04 g/mol
Ice Water Bath (H2O)
Boiling Stone

The reagents are to be in a 1:1 molar ratio. The limiting reagent is 2-methylcyclohexanol because it required the least mol amount to complete the reaction.

Product Data from Literature:
Major Product: 1- methylcyclohexene
Minor Product: 3- methylcyclohexene
Molecular Formula: C7H12
Molecular Weight: 96.17 g/mol

Theoretical Yield: The products are always in a 1:1 molar ratio with 2-methylcyclohexanol.

2-methylcyclohexanol: 5.66 g x 1mol = .0496 mol of 2-methylcyclohexanol
114.19 g
*Since the reaction goes through a 1:1 molar ratio, .0496 mol of 2-methylcyclohexanol should yield .0496 mol of methylcyclohexene*

methylcyclohexene: .0496 mol of methylcyclohexene x 96.17 g = 4.77 g of methylcyclohexene
1 mol
Literature Value of Boiling Point: 1- methycyclohexene: 110oC
3- methycyclohexene: 104oC

Balanced Chemical Equations


Experimental Procedure: (as per lab handout)

1)Add 6 mL of 2-methylcyclohexanol, 5 mL of 85% phosphoric acid and a boiling stone to a 25 mL round bottom flask. 2)Set up the flask and also start setting up the distillation...
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