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CIE Jun 2016 v2 Paper 2 Q5
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![PMT reaction 4 CH3CH2CH2 Br A reaction sequence based on propan-1-ol is shown. 10 CH3CH CH2 reaction 3 CH3CH2C OH reaction 1 CH3CH2CH2 OH propan-1-ol reaction 2 CH3CH2C reaction 5 NaCN / H+ OH CH3CH2C CN (a) Reactions 1 and 2 can both be carried out using the same reagents. (i) Identify suitable reagents for reactions 1 and 2.[1] (ii) State and explain how the reaction should be carried out to ensure that reaction 2 rather than reaction 1 occurs.[2] (b) Identify the necessary reagents and conditions for each of reactions 3 and 4. reaction 3reaction 4[2]UCLES 2016 9701/22/M/J/16<br />
(c) (i) Complete the reaction mechanism for reaction 5. Include all relevant lone pairs, curly arrows, charges and partial charges. 11 PMT CH3CH2 OC NC CH3CH2 OH CN The product of reaction 5 exhibits stereoisomerism. (ii) Draw the two stereoisomers in the conventional way. [4] [2] (iii) Suggest why a mixture of the two stereoisomers is formed by reaction 5.[2] [Total: 13]UCLES 2016 9701/22/M/J/16 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v2_QP_-_Paper_2_CIE_Chemistry_A-level_5-0.jpg)
![Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMay/June 2016 9701 22 PMT Answer Mark Total [1] [1] [1] [1] [1] [2] [2] [1] [2] [1] [1] [1] [3] [Total 9] [1] [1] [1] [1] [2] Question (a) CH3CH2CH2COOH (CH3)2CHCOOH / CH3CH(CH3)COOH (b) (i) Two from 1. CH3CH2COOCH3 2. CH3COOCH2CH3 3.HCOOCH2CH2CH3 (ii) correct acid + alcohol for either ester 1. methanol + propanoic acid 2. ethanol + ethanoic acid 3. propan-1-ol + methanoic acid (conc)H2SO4 / (conc)H3PO4 AND heat / warm / reflux (c) Peak at 17101750 (for ester) due to C(=)O Peak at 15001680 (for X) due to C(=)C / alkene Peak at 32003650 (for X) due to (alcohol) O()H (a) (i) acidified / H AND potassium / sodium dichromate (ii) distillation (rather than reflux) (ensures aldehyde escapes) to avoid further oxidation / to avoid forming acid / as reflux causes further oxidationCambridge International Examinations 2016<br />
Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMay/June 2016 9701 22 Question Answer Mark Total PMT (b) reaction 3(conc) H2SO4 / (conc) H3PO4 or Al 2O3 / pumice / porcelain / porous pot / ceramic AND heat reaction 4KBr / NaBr with (conc) H2SO4 or (red)P and Br2 / PBr3 (c) (i) AND heat CH CH +N C CH CH CN OH CH CH CN M1 = lone pair on C of CN AND curly arrow from lone pair to carbonyl carbon M2 = dipole on C=O AND curly arrow to O from = M3 = intermediate with negative charge M4 = lone pair and curly arrow to H (ii) OH OH CN CN CH CH CH CHCambridge International Examinations 2016 [1] [1] [1] [1] [1] [1] [1+1] [2] [4] [2]<br />
Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMay/June 2016 9701 22 Answer Mark Total PMT attack / attach from either side / above or below / from two directions because the carbonyl / molecule is planar / trigonal / flat / because of the shape of the molecule [1] [1] [2] [Total 13] Question (iii) OR product is chiral / has a chiral carbon / has a carbon attached to four different groups / has a chiral centre / is asymmetric (equal) chance of forming either (of the two optical isomers) / mechanism doesnt distinguish between the two (optical isomers) / able to form either / chance of forming / able to form 50:50 OR because the carbonyl / molecule is planar / trigonal / flat OR because of the shape of the molecule (equal) chance of forming either (of the two optical isomers) / mechanism doesnt distinguish between the two (optical isomers) / able to form either / chance of forming / able to form 50:50Cambridge International Examinations 2016<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v2_MS_-_Paper_2_CIE_Chemistry_A-level_5-0.jpg)
