AQA Jun 2017 Paper 2 Q7

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12 Alcohols undergo dehydration in the presence of concentrated phosphoric acid, via a carbocation intermediate, to form alkenes. Complete the mechanism for the conversion of 2-methylcyclohexanol into 1-methylcyclohexene via carbocation D by drawingthe structure of the missing intermediateall necessary curly arrows. [4 marks] carbocation D carbocation D Draw the structure of a different cyclic alkene formed from carbocation D. [1 mark] 0 7 0 7 . 1 0 7 . 2 *12* IB/M/Jun17/7404/2<br /> 130 7 . 3 Carbocation D can undergo a type of reaction called a rearrangement to form carbocation E. In this reaction, a hydrogen atom and its bonding pair of electrons move from carbon a to carbon b as shown in Figure 2. Figure 2 carbocation D Use your knowledge of carbocations to explain why this rearrangement takes place. carbocation E [2 marks] 0 7 . 4 As a result of the rearrangement in Question 7.3, a third alkene is formed in this reaction. Draw the structure of this third alkene. [1 mark] Turn over for the next question *13* Turn overIB/M/Jun17/7404/2<br /> 140 7 . 5 Cyclohexene is prepared by the dehydration of cyclohexanol using concentrated phosphoric acid as a catalyst. The structure of concentrated phosphoric acid is shown. [6 marks] Identify the factors that influence the boiling points of each of the compounds in this reaction mixture. State how and explain why cyclohexene can be separated from the reaction mixture. *14* 14 IB/M/Jun17/7404/2<br />

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