cyclohexene - Chem 267 Cyclohexene(revised 7/10 In this...

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Chem 267 . Cyclohexene . (revised 7/10). In this experiment you will synthesize cyclohexene and purify it by distillation. You will check the purity and identity of the product by gas chromatography (GC) and infrared spectroscopy (IR). You will also do some simple chemical tests which distinguish alkenes from alkanes. Review the chapter on distillation and your notes from the distillation experiment. The "Things to Watch Out For in Distillations" listed for the distillation experiment are common to this distillation as well. As always, use care when inserting the thermometer into the thermometer adaptor. Hold the thermometer close to the adaptor and push and twist gently. Breakage could result in a serious injury. Check for frayed connectors and cracked flasks. Cyclohexene has a disagreeable odor, characteristic of volatile alkenes. Allow the apparatus to cool before disassembling it in the hood, and dispose of the wastes in the hood in the PROPER CONTAINERS (see below). Rinse the apparatus with a LITTLE acetone and dispose of that in the Nonhalogenated Liquid Waste container. CAUTION: cyclohexene is very flammable. Handle phosphoric acid with care. It is corrosive to tissue. If your skin comes into contact with phosphoric acid, wash the contaminated area immediately with water, then soap and water. Clean up spills immediately using the sodium bicarbonate in the hood. Do the Prelab Exercise on p. 334 (a model of a flow sheet is on p. 142). This is something to do for all synthesis experiments. Also always prepare a table of reactants and products such as that shown in the handout, “Sample Notebook and Report”. Preparation of Cyclohexene . As always, if a sand bath is needed, turn it on and set it to about 35 immediately. The phosphoric acid need not be measured very accurately. However, the amount of cyclohexanol determines the theoretical amount of product so it must be measured accurately. To measure the reagents do the following: Place the round-bottomed (RB) flask into a 30 mL beaker to hold it upright, tare the beaker and flask, and weigh in about 2.0 g (± 0.05 g, but weigh it exactly, e.g., 1.96 g) of cyclohexanol by dropping it in with a pipet. Using a buret in the hood, add about 0.5 mL of 85% phosphoric acid to the RB flask. Note that the flask becomes warm - addition of acid to alcohol is exothermic. Set up the fractional distillation apparatus exactly as for the distillation experiment, not as that shown in Fig. 19.1 (don’t forget a couple of boiling chips). Be sure to use the distillation column, not the longer chromatography column - the chromatography column does not connect tightly. Use the black plastic connector to connect the flask to the distilling head. This is more resistant to the reactants than is the white connector. Insulate the column by loosely wrapping it with a piece of aluminum foil (not glass wool or cotton). Use an ice-cooled receiver. Otherwise product will evaporate (result: lower yield and increased stench in room). Heat the mixture sufficiently to distill product over into the collection vial (remember to lower the distilling
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cyclohexene - Chem 267 Cyclohexene(revised 7/10 In this...

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