CIE Nov 2017 v2 Paper 4 Q7

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(a) Calcium carbide, CaC2, reacts readily with water, forming ethyne, C2H2, and a sparingly soluble white ionic compound. 15 PMT (i) Write an equation for the reaction of CaC2 with water.[1] (ii) Draw a dot-and-cross diagram for the carbide ion, C2 2. Show outer electrons only. [1] (b) Ethyne is the simplest member of the alkyne homologous series. ethyne Propyne, C3H4, and butyne, C4H6, are the next two members of the series. Deduce the general formula for the alkynes.[1] (c) Ethyne can be polymerised into poly(acetylene), which is a conducting polymer. n poly(acetylene) (i) Suggest why this polymer conducts electricity.[1] (ii) State the empirical formula of poly(acetylene).[1] (iii) By reference to a physical or chemical property, suggest one advantage of a conducting polymer when compared with metals.[1]UCLES 2017 9701/42/O/N/17 [Turn over<br /> (d) Alkynes can react with carbonyl compounds under basic conditions as shown in reaction 1. 16 PMT R' R'' small amount of base R' OH R'' reaction 1 (i) The first step of the mechanism of reaction 1 involves the alkyne anion reacting with the carbonyl compound. Complete the first step of the mechanism and draw the intermediate for this reaction. Include all relevant dipoles, charges and curly arrows. R' R'' C intermediate R' OH R'' [3] (ii) Suggest the name of the mechanism in reaction 1.[1]UCLES 2017 9701/42/O/N/17<br /> (iii) An alkyne, Q, and a carbonyl compound, R, react together to form compound P as shown. 17 PMT 2Q + R C2H5C C2H5C OH CH3 CH2 CH3 OH Use reaction 1 to suggest the structures of Q and R. [2] (e) A series of twelve separate experiments is carried out as shown in the table. Complete the table by writing in each box a tick () if a reaction occurs, or a cross ( ) if no reaction occurs. CH3CHO HCO2H CH3COCH3 HO2CCO2H hot, acidified MnO4 (aq) alkaline I2(aq) warm Tollens reagent [4] [Total: 16]UCLES 2017 9701/42/O/N/17 [Turn over<br />

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