6 small amounts of other impurities are mixed in with

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6 small amounts of other impurities are mixed in with the cyclohexene product. Water will interfere with the final distillation so it must be removed completely. To do this, add saturated aqueous sodium chloride solution to the reaction tube, the volume being about equal to the volume of liquid already in the tube. Mix the two layers thoroughly by drawing some of the lower up into the pipet and expelling it back through the solution repeatedly for a couple of minutes. This procedure is called washing or extracting and will be used in several future experiments. The technique will be demonstrated by your TA. Washing with saturated sodium chloride solution is a pre-drying step that removes most of the water from the organic phase. Remove the lower aqueous (NaCl) layer with a pipet and temporarily place it into another container, being very careful to remove all of the lower layer but none of the upper organic layer. Using a clean dry pipet transfer the organic layer to a clean dry vial (do a transfer rinse using a few drops of toluene). There should be no droplets of water present at this point. If there are carefully remove all visible droplets of water. Add several spheres of calcium chloride drying agent to the vial, cap the vial, and swirl the contents well to be sure that all of the liquid comes into contact with the drying agent. Notice that the spheres clump together. This indicates that the drying agent is doing its job and has absorbed water. To be sure that enough drying agent has been added, add an additional few spheres of calcium chloride, swirl, observe, and continue this until the newly added spheres no longer clump together. The danger of adding too much drying agent is that it also absorbs the product and can lead to loss. (If all the visible droplets of water were not completely removed first, instead of clumping together, the first few spheres of drying agent will break apart and form a cloudy looking mass (layer) at the bottom of the vial. In such a case carefully pipet the contents to another clean dry vial, leaving behind the cloudy layer. Do a transfer rinse with a few drops of toluene then add drying agent in small amounts as before until a few of the spheres no longer clump together.) Set the capped vial into a small beaker for safe keeping and allow the solution to dry for at least five minutes. During this time the fractional distillation apparatus should be cleaned and dried. Water has been carefully removed from the organic product mixture, so it is important to not reintroduce any water to the mixture. To obtain pure product, the final distillation must be done carefully using clean, dry equipment. Rinse the apparatus first with water, then a little ethanol and then a little acetone to speed up the drying process. Blow air gently through and over the apparatus in the hood to evaporate the solvents. The column is most effectively dried by drawing air through it using the vacuum connection. It is essential to remove all water and organic solvents before the final distillation. It is however not necessary to FILL the glassware with cleaning solvent. This would be extremely wasteful. Add a small amount of solvent, swirl it around and while pouring it into the waste container, turn the apparatus so that solvent comes into contact with the entire apparatus.
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