Repeat this once more again with just a small amount

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container, turn the apparatus so that solvent comes into contact with the entire apparatus. Repeat this once more, again with just a small amount of solvent. (Remember to always try to be environmentally responsible by minimizing waste.) A final fractional distillation must now be done carefully to separate the chaser and any small amounts of other impurities from the product. Pipet the organic product mixture into the 5 mL rb flask, leaving the calcium chloride behind (do another transfer rinse) and distill the mixture carefully through the fractionating column. This fractional distillation is essentially the same as that of cyclohexAne and toluene that you did in experiment one. This time however you will collect the cyclohexEne as a pure fraction in a clean, dry, tared vial. You need not count drops of distillate. In a distillation such as this, the idea is to separate lower-boiling and higher-boiling impurities from the desired product. To do this, do not collect distillate as product until the thermometer reaches the BP of the product (± about 3° C) (in this case the product is cyclohexene). That is, first have an "impurities" vial attached to the apparatus to collect low-boiling impurities (if any). When the temperature of distillate closely approaches the BP of product, replace the "impurities" receiving vial with a clean, dry,
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7 tared "product" vial. Collect distillate as product while the temperature remains at the BP of product (± about 3° C). Once the temperature rises steeply above the BP plateau of the product, replace the vial with the "impurities" vial once again to collect any higher-boiling distillate, then stop the distillation by lifting the apparatus away from the heat. Cap the product vial to prevent evaporation and weigh it. Note that the temperature may fluctuate by a few degrees during collection of the product - this is okay. As an example look at the following figure. In this example, “pure” cyclohexene would be collected in vial 1 from 0-55 drops (BP 83). Once the temperature rises steeply after about 55 drops, pure cyclohexene is no longer distilling. Material between 55 and 68 drops (BP 83-111) is a mixture of cylcohexene and toluene. After about 68 drops, pure toluene would distill. Because in our experiment we simply want to obtain pure cyclohexene, the distillation can be stopped as soon as the temperature begins to rise sharply after about 55 drops in this example. You need not construct a graph such as this but you should keep in mind that this is what is happening as you distill. At this point the product should be clear, not cloudy (clear does not mean colorless). Cloudiness indicates the presence of water, which must be removed completely before GC analysis. If the product is cloudy, add more drying agent, swirl and let stand for a few minutes, then transfer the product to a clean dry vial. In some cases the product may need to be redistilled (check with TA if still cloudy). Sign up for the GC analysis then continue working on the experiment or cleaning your equipment until you are called to carry out the GC analysis – do not waste time waiting in line. Demonstrate the presence of the alkene functional group by testing your product with bromine and permanganate as described below.
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