CIE Jun 2017 v2 Paper 4 Q3

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(a) In a molecule of SOCl 2 the sulfur atom has four bonds. Draw a 'dot-and-cross diagram of SOCl 2. Show the outer shell electrons only. PMT [2] (b) When SOCl 2 is reacted with a carboxylic acid to produce an acyl chloride, two acidic gases are formed. SOCl 2(l) + RCO2H(l) RCOCl (l) + SO2(g) + HCl (g) A 1.00 g sample of a carboxylic acid RCO2H was treated in this way, and the gases were absorbed in 60.0 cm3 of 0.500 mol dm3 NaOH(aq), an excess. (i) Write equations for the reactions between NaOH and HCl ,NaOH and SO2.[2] The excess NaOH was titrated with 0.500 mol dm3 H+(aq). It required 10.8 cm3 of the H+(aq) solution to reach the end-point. (ii) Calculate the total number of moles of NaOH that reacted with the SO2 and HCl. (iii) Calculate the number of moles of RCO2H that produced the SO2 and HCl. moles of NaOH =[2] moles of RCO2H =[1]UCLES 2017 9701/42/M/J/17<br /> PMT (iv) Hence calculate the Mr of the carboxylic acid, RCO2H. Mr RCO2H =[1] (v) The R group contains carbon and hydrogen only. Suggest the molecular formula of RCO2H.[1] (c) The following synthetic route shows how a carboxylic acid can be converted into an amine. SOCl 2 CH3CO2H CH3COCl NH3 CH3CONH2 step 3 CH3CH2NH2 (i) Suggest a reagent for step 3.[1] Angelic acid, C5H8O2, is a natural product isolated from the roots of the angelica plant.Angelic acid reacts with H2 + Ni to form T, C5H10O2. T undergoes the above synthetic route to form the amine U, C5H13N. U can also be made by reacting 1-bromo-2-methylbutane with ammonia. Both angelic acid and T exist as stereoisomers. (ii) Suggest structures for angelic acid, T and U. angelic acid (iii) State the type of stereoisomerism shown by angelic acid and T. angelic acidcompound T[1] [3]UCLES 2017 9701/42/M/J/17 [Total: 14] [Turn over<br />

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