To carry out the dehydration of 2-methylcyclohexanol and study the orientation of C=C in the final alkene products. Saytzev°s rule will be tested. Introduction:
Alcohols can be dehydrated by using an acid such as sulfuric or phosphoric acid. Water will be eliminated from the molecule and a C=C double bond will be formed. If the alcohol is not symmetric, then a mixture of products containing alkene isomers is possible. Russian chemist Saytzev predicted that for a reaction following E1 mechanism, the more substituted C=C is favored in the product. In the case of 2-methylcyclohexanol, that would mean that 1- methylcyclohexene should be formed as the major product. Therefore, in this experiment, we will carry out the dehydration of 2-methylcylclohexanol in H3PO4/H2O, and analyze the distribution of alkene products on a GC. The result would allow us to test whether the Saytzev°s rule holds in this case.
Experimental: (note: past tense and passive)
2 ml of cyclohexanol was mixed with 0.6 ml of 85% H3PO4 and the mixture was swirled to for 2-3 min to allow the reaction to complete. A distillation was then set up. The setting of the Variac was controlled so that the thermometer temperature of the vapor distilled was below 100 !C. The distillate was washed with NaCO3 and water, before being dried over CaSO4. 0.5 grams of colorless liquid product were obtained and kept in a vial. The product was analyzed by injecting 1 ul of sample into the GC.
The product was also tested for the presence of a C=C double bond. It was found that our product discolored the purple color of KMnO4 upon its addition and it also discolored the brown color of Br2/Cl4.
Results and Discussion:
Based on the amount of product obtained, the % yield of this reaction is calculated as follows:
(show the calculation either with handwriting or typing. Let°s assume a yield of 35%)The yield is somewhat low; this could be due to the incomplete reaction or...
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