STEP 1: Place 25.0 g (31 ml, 0.28 mol) of 2-methylbutan-2-ol and 10 ml of 85 per cent orthophosphoric acid in a 100-m1, round-bottomed flask and swirl to mix thoroughly.
STEP 2: Fit the flask with a 20-cm fractionating column filled with glass helices, a Claisen still-head and a condenser leading to a 50-m1 receiving flask cooled in a beaker of iced water.
STEP 3: Add a few pieces of porous porcelain and heat the reaction mixture gently with a Bunsen burner.
STEP 4: Collect the alkene fraction which distils in the range 35-38 °C during a period of 30 minutes.
STEP 5: Dry the distillate with 1-2 g of magnesium sulphate.
STEP 6: Wash and dry the distillation apparatus, decant the dried distillate into a 50-m1 flask and redistil in the reassembled apparatus.
STEP 7: Collect the fraction boiling at 37-38 °C; the yield is 12.5 g (64%). Record the infrared spectrum of the product using a fixed path-length cell (0.025 mm).
STEP 8: The stretching bands of the terminal (1645 cm '} and non-terminal (1670 cm ') carbon–carbon double bonds can both be observed; bands at 890 and 805 cm (=C—H deformation) also establish the presence of both terminal and non-terminal olefinic systems.
STEP 9: Analyse the product by g.l.c. on a Silicone oil column at 30 °C; 2- methylbut-1 -ene appears first, closely followed by 2-methylbut-2-ene; the areas under the peaks are in the ratio of 1:4.
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