Edexcel Jun 2014 (R) Paper 2 Q19

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SECTION C Answer ALL the questions. Write your answers in the spaces provided. 19 Insect-borne diseases, such as malaria, affect the lives of millions of people. Chemists are constantly finding new compounds to combat the transmission of these diseases. One such compound is the insect repellent commonly called p-menthane-3,8-diol (this is not its systematic name). It is used to protect both humans and animals. The structure of p-menthane-3,8-diol is shown below. HO HO p-menthane-3,8-diol is found naturally in the leaves of Eucalyptus citriodora, which is native to Australia and is commonly known as Lemon Bush. It can be extracted from these leaves but is currently commercially prepared by chemical synthetic pathways. However, the commercially-made chemical has been found by some scientists to be less effective than the natural leaf extract. It is possible that p-menthane-3,8-diol can kill microorganisms and it is this additional potential use and others which are being investigated by the chemical industry. p-menthane-3,8-diol should not be confused with either methane or methanol. (a) p-menthane-3,8-diol has two alcohol functional groups. Classify the type of alcohol group on the far left of the structure drawn above and explain the meaning of the term functional group. (2)(b) Give the molecular formula of p-menthane-3,8-diol. (1)*P42991A01924* 19 Turn over<br /> (c) p-menthane-3,8-diol is found in the oily extract from the leaves of the Lemon Bush. One method used to extract the oil is described below. Initially, the leaves are ground up using a pestle and mortar with some sand and an organic solvent, such as cyclohexane. (i) Suggest why sand is used. (1)*(ii) The solvent cyclohexane forms intermolecular forces with other organic molecules when they dissolve. Identify these intermolecular forces and explain how they arise. (3) Type of intermolecular forceHow they arise(iii) How could the sand and other solid residue be removed from the mixture? (1)(iv) At this stage, either anhydrous magnesium sulfate or calcium chloride is added. Suggest the reason for this. (1)20 *P42991A02024*<br /> *(v) A student suggested using the following apparatus to remove the cyclohexane from the mixture. water out pear-shaped flask open top Liebig condenser water in anti-bumping granules HEAT Explain, in terms of the processes that occur in the above apparatus, why this method is unsuitable to remove the cyclohexane. Suggest how this apparatus could be adjusted for a successful separation. DATA (cid:116) Boiling temperatures: p-menthane-3,8-diol 266 C; cyclohexane 81 C (4)*P42991A02124* 21 Turn over<br /> (d) Spectroscopic techniques can be used to confirm the presence and identity of organic molecules such as p-menthane-3,8-diol. (i) Suggest how infrared spectroscopy could be used to confirm the presence of the functional group in a molecule such as p-menthane-3,8-diol. (1)(ii) Suggest the identity of two fragment ions, with a m/e value of more than 13 but less than 20, that could be observed in a mass spectrum of p-menthane-3,8-diol. (2) First fragment ionSecond fragment ion(e) One reason why the synthetic p-menthane-3,8-diol may be less effective than the natural extract is because there are many isomers of this molecule. Complete the structures below to show two structural isomers of p-menthane-3,8-diol which have the same number of alcohol functional groups and the same carbon skeleton. (2) p-menthane-3,8-diol HO HO HO HO 22 *P42991A02224*<br /> *(f) State two key principles of sustainability, and how the chemical industry might achieve these, when mass-producing a molecule such as p-menthane-3,8-diol. (4) Principle 1Principle 2(Total for Question 19 = 22 marks) TOTAL FOR SECTION C = 22 MARKS TOTAL FOR PAPER = 80 MARKS *P42991A02324* 23<br />

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