Dehydration of 2-Methylcyclohexanol

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Dehydration of 2-Methylcyclohexanol Abstract The goal of this lab was to dehydrate 2-Methylcyclohexanol to obtain a cyclohexene using a concentrated acid. The percent yield for the final product was 69.6% and both saturation tests were positive for the presence of a double bond. The IR spectroscopy produced peaks between 1400 and 1600 cm-1, which suggests the presence of C=C double bonds. Introduction In this lab an alcohol is dehydrated using concentrated phosphoric acid, and sulfuric acid as a catalyst. The acid protonates the hydroxyl group, which creates water, a good leaving group. A beta hydrogen is then involved in the E1 process and a C=C double bond is formed. Since the starting material is not symmetric we obtain a mixture of products, with 1-Methylcyclohexene as the major product according to Zaitsev’s Rule. (1) The product is obtained by distillation, where it is accompanied by water and some phosphoric acid. Because of this, anhydrous sodium sulfate is used to remove the water from the solution. Aqueous sodium bicarbonate is used to neutralize the acid, resulting in the racemic mixture of methylcyclohexenes. To ensure that this process is successful one can administer unsaturation tests to determine if double bonds were formed. Compounds containing double bonds react with a red bromine solution and decolorize it. A similar reaction occurs when adding potassium permanganate, with an added brown precipitate forming. (2) Another qualitative test, IR spectroscopy, can be performed to check for the presence of C=C double bond by looking out for peaks between 1400-1600 cm-1. Experimental Procedures 750µL of 2-Methylcyclohexanol were added to a 5-mL conical vial, which contained a magnetic stirring bar. 225µL of phosphoric acid were then added to the conical vial using a micropipette. A fractional distillation apparatus with a Hickman still was

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