11983.05R 13 α-Terpineol is a terpene which is the main ingredient in pine oil. OH α-terpineol It is a colourless liquid with a smell of violets. The boiling point of α-terpineol is 214–216 °C and its density is 0.93 g cm−3. α-Terpineol is slightly soluble in water; 2.42 g dissolves in 1 dm3 of water at room temperature. (a) (i) Describe and explain, using calculated values, what you would observe if you added 1.1 g of α-terpineol to 200 cm3 of water in a beaker at room temperature and stirred the mixture. [4] 11983.05R [Turn over (ii) Explain, with full experimental detail, how you would separate α-terpineol from a mixture of 50 cm3 of α-terpineol and 10 cm3 of water. Your method should include separating with a funnel, distillation and drying. In this question you will be assessed on your written communication skills including the use of specialist scientific terms. [6] 11983.05R (b) The purity of the α-terpineol obtained from part (a) may be determined by the infrared spectrum which is shown below. transmittance wavenumber (cm−1) 3000 2000 1000 0.8 0.6 0.4 0.2 (i) Explain why molecules absorb infrared radiation producing infrared spectra. [2] (ii) Identify the peaks, by stating the range of wavenumbers in the spectrum, which correspond to the functional groups in the molecule. [2] "Data from NIST Standard Reference Database 69: NIST Chemistry WebBook © National Institute of Standard and Technology. U.S. Department of Commerce" 11983.05R [Turn over (iii) Explain how you could use infrared spectrometry to determine that a sample of α-terpineol is pure and free from all impurities. [1] (c) (i) Explain, using the structure of α-terpineol, whether the alcohol is primary, secondary or tertiary. [2] (ii) State what would be observed when a few drops of α-terpineol are added to acidified potassium dichromate(VI) and the mixture is heated. [1] 11983.05R (d) When α-terpineol is dehydrated it forms a mixture of limonene and δ-terpinene. limonene Suggest the structure of δ-terpinene. [1] (e) Limonene is an unsaturated hydrocarbon which reacts with bromine and hydrogen. (i) Define the term unsaturated. [1] 11983.05R [Turn over (ii) Explain, giving experimental detail, how you would use bromine water to test for unsaturation. [3] (iii) Explain, naming the catalyst, what is meant by catalytic hydrogenation. [2] (iv) Cadinene, C15H24, reacts with hydrogen and becomes completely saturated. 0.34 g of cadinene reacts with 80 cm3 of hydrogen at 20 °C and a pressure of one atmosphere. Calculate the number of double bonds in a molecule of cadinene. [3]