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CIE Jun 2017 v1 Paper 4 Q6
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![PMT The reaction between 1-chloro-1-phenylethane and hydroxide ions to produce 1-phenylethanol is: 14 C6H5CHCl CH3 + OH 1-chloro-1-phenylethane C6H5CH(OH)CH3 + Cl1-phenylethanol The rate of this reaction can be studied by measuring the amount of hydroxide ions that remain in solution at a given time. The reaction can effectively be stopped if the solution is diluted with an ice-cold solvent. (a) Describe a suitable method for studying the rate of this reaction at a temperature of 40 C, given the following.a solution of 0.10 mol dm3 1-chloro-1-phenylethane, labelled A a solution of 0.10 mol dm3 sodium hydroxide, labelled B 0.10 mol dm3 HCl volumetric glassware ice-cold solvent stopclock access to standard laboratory equipment and chemicals[4] (b) The rate of this reaction was measured at different initial concentrations of the two reagents. The table shows the results obtained. experiment [C6H5CHCl CH3] / mol dm3 [OH] / mol dm3 relative rate 1 2 3 4 0.05 0.10 0.15 0.20 0.10 0.20 0.10 0.15 0.5 1.0 1.5 to be calculated (i) Deduce the order of reaction with respect to each of [C6H5CHCl CH3] and [OH]. Explain your reasoning. order with respect to [C6H5CHCl CH3]order with respect to [OH][2]UCLES 2017 9701/41/M/J/17<br />
PMT 15 (ii) Write the rate equation for this reaction, stating the units of the rate constant, k. rate =mol dm3 s1 units of k =[1] (iii) Calculate the relative rate for experiment 4. (c) (i) Use your answers in (b)(i) to help you to draw the mechanism for the reaction of 1-chloro-1-phenylethane with hydroxide ions, including the following. relative rate for experiment 4 =[1]all relevant lone pairs and dipoles curly arrows to show the movement of electron pairs the structures of any transition state or intermediate (ii) This reaction was carried out using a single optical isomer of 1-chloro-1-phenylethane. Use your mechanism in (i) to predict whether the product will be a single optical isomer or a mixture of two optical isomers. Explain your answer.[1] [3]UCLES 2017 9701/41/M/J/17 [Turn over<br />
PMT 16 (d) The proton NMR spectrum of a sample of 1-phenylethanol shows four peaks: a multiplet for the C6H5 protons and three other peaks as shown in the table. When the sample is shaken with D2O and the proton NMR spectrum recorded, fewer peaks are seen. Complete the table for the proton NMR spectrum of 1-phenylethanol, C6H5CH(OH)CH3. Use of the Data Booklet might be helpful./ ppm number of 1H atoms responsible for the peak group responsible for the peak splitting pattern result on shaking with D2O 1.4 2.7 4.0 7.2-7.4 C6H5 multiplet peak remains [4] [Total: 16] Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.UCLES 2017 9701/41/M/J/17<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_v1_QP_-_Paper_4_CIE_Chemistry_A-level_6-0.jpg)
![9701/41 Question 6(a) Cambridge International AS/A LevelMark Scheme PUBLISHED Answer May/June 2017 Marks titrate against HCl repeat at time at known time intervals Any of the three methods possible. Any 4 of the 5 points for each method available for maximum 4 marks. Method 1 1 Ensure both solutions (A and B) at 40 C before mixing 2 mix known volumes of A and B and start the clock 3 at known time take out a sample / X and add it to ice-cold solvent 4 5 Method 2 1 Ensure both solutions (A and B) at 40 C before mixing 2 mix known volumes of A and B and start the clock 3 at known time pour into ice-cold solvent or pour ice-cold solvent in 4 5 Method 3 1 Ensure both solutions (A and B) at 40 C before mixing 2 mix known volumes of A and B and start the clock and add pH meter 3 at a known time . . . . 4 5 titrate against HCl repeat with different concentrations of either A or B, or repeat using different times . . . . record the pH repeat pH readings at known time intervals 6(b)(i) from 1 and 3: when [RCl ] is trebled, so is rate, so order w.r.t. [RCl ] = 1 from 1 and 2: when both concentrations are doubled, rate doubles so [OH] has no effect on rate, so order w.r.t.[OH] = 0 6(b)(ii) rate = k[RCl ] AND units: sec1 1 / s 6(b)(iii) relative rate = 2.0UCLES 2017 Page 10 of 12<br />
9701/41 Question 6(c)(i) 6(c)(ii)UCLES 2017 Page 11 of 12 Cambridge International AS/A LevelMark Scheme PUBLISHED Answer May/June 2017 Marks C-Cl dipole and first curly arrow intermediate cation OH with lone pair and curly arrow Beginning with candidates mechanism in (c)(i): If SN1: racemate / mixture of / two optical isomers will be formed, because: the intermediate is planar / has a plane of symmetry / OH can approach from top or bottom or from any direction If SN2: one optical isomer because attack always from fixed direction / from same side / the configuration always inverts / there is an asymmetric transition state<br />
9701/41 Question 6(d)(i) the three groups are in their correct places wrt thevalues no. of H atoms for each peak agrees with group column splitting patterns doublet, singlet and quartet are assigned to correct groups peak identified as OH disappears with D2O, no other peak disappears Cambridge International AS/A LevelMark Scheme PUBLISHED Answer May/June 2017 Marksvalue number of H atoms 1.4 2.7 4.0 3 1 1 group CH3 / methyl OH / hydroxyl / alcohol CH splitting doublet singlet quartet result with D2O peak remains peak disappears peak remains Total: 16UCLES 2017 Page 12 of 12<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_v1_MS_-_Paper_4_CIE_Chemistry_A-level_6-0.jpg)
