4-Methylcylohexene Lab Report

Discussion
The dehydration of an alcohol to an alkene follows a two step elimination reaction. The first step is determines the rate of the reaction and is dependent on the formation of the carbocation. In this experiment, the carbocation intermediate forms as the alcoholic hydroxyl group is protonated with acid, and dihydrogen oxide leaves. After this unimolecular dissociation step, a proton from one of the adjacent carbons is captured to reform the acid catalyst, and the elimination reaction is complete with the formation of the double bond. Water is distilled out of the reaction to promote a high yield of 4-methylcylohexene. By removing water, the reaction is forced in the forward direction due to Le Châtelier’s Principle. In order to determine
A theoretical mass of 1140 mg and an experimental mass of 263 mg resulted in a 23.1% yield. This low percent yield is most likely due to error in the experiment. The potassium permanganate test was positive for the presence of a double bond in the product as brown precipitate formed along with the discoloration of the solution. An IR spectroscopy of the product was also performed. Results of the IR absorptions of this experiment were compared to the IR absorptions of standard functional groups as identified by the University of Puget Sound. Three main absorption bands were formed at 3373.46 cmˉˡ, 1635.71 cmˉˡ, and 1101.39 cmˉˡ. The absorption band at 3373.46 cmˉˡ is between the ranges of 3200-3600 cmˉˡ which indicates the presence of an alcohol. Ideally, this reaction would only result in 4-methylcyclohexene. However, the presence of alcohol signifies a partial or incomplete reaction. The absorption band at 1635.71 cmˉˡ is between the ranges of 1620-1680 cmˉˡ which correlates to a carbon double bonded to a carbon. This result coincides with the potassium permanganate test as it expresses the existence of an alkene product. The last absorption band falls between the ranges of 1050-1150 cmˉˡ which denotes a carbon bonded to an alcohol. Again, this could be due to an incomplete or partial reaction. There is a strong unidentified peak before 1000 cmˉˡ which could indicate a carbon bonded hydrogen in an alkene as it
Alcohol could have been co-distilled out during the reaction as a temperature over 173°C is past the boiling point of alcohol. This could have occurred as the range of heating was set between 160-180°C. As a result, an improvement would be to shrink the range down to 160-170°C. Maintaining a consistent temperature is also difficult and could be improved through the careful use of an oil bath. Other error in this experiment explains the low percent yield. Product is inevitably lost through the extraction process. It is impossible to completely transfer the entire product during extraction, and as a result some product is lost. Additionally, product is lost during the decantation process as the narrow test tube allows the liquid product to get trapped by the anhydrous sodium sulfate particles.
The product, 4-methylcyclohexene, has a citrus aroma that is useful in perfumery and can be used to scent cosmetics (The Good Scents Company). However, the dehydration process from an alcohol to an alkene is useful in synthesizing various types of alkenes with unique properties. This elimination process could simply be used to synthesize other alkenes for industrial or lab purposes. More specifically, alkenes are used in the polymerization of plastics. Ethanol can be dehydrated to ethene. Polyethene is used in the manufacturing of raincoats, shoe soles, pipes, and floor tiles (Preserve