OCR A Jun 2015 Paper 4 Q3 (with explained solutions) |

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OCR A Jun 2015 Paper 4 Q3

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3 Many -amino acids have several functional groups. 10 (a) Serine, shown below, is a naturally occurring -amino acid. (i) In the boxes below, draw the structure of the organic compounds formed by each reaction. HO OH H H C C NH2 H serine Na2CO3(aq) reaction 1 reaction 2 HO CH2 and H2SO4 (ii) Suggest a use for the organic compound formed by reaction 2.[1] [3] (iii) Serine is commonly used in organic synthesis. One possible method of synthesising serine is shown below. CH3COO H C H H C Cl H C H OH reaction 3 CH3COO HO OH H H C C NH2 H serine reaction 5 CH3COOOCR 2015 H C H H C H H C NH2 H C H OH reaction 4 H C NH2 OH<br />
11 Complete the following: Reagent and conditions used for reaction 3.Type of reaction for: reaction 4reaction 5[3] (b) Compound E, C4H7NO, is one of two optical isomers. It can be oxidised by Tollens reagent to an -amino acid, F. The -amino acid F forms two different polymers, G and H. Polymer G has the empirical formula C4H7NO2. Polymer H has the empirical formula C4H5NO. Suggest structures for compound E and compound F.Draw repeat units of polymer G and polymer H.Describe how F forms G and H.OCR 2015 [6] Turn over<br />
(c) Poly(glutamic acid) is a polymer of the amino acid, glutamic acid. 12 H H N C HOOC H C H H C H O C repeat unit of poly(glutamic acid) (i) Draw the structure of glutamic acid. (ii) A student tried to prepare poly(glutamic acid) from glutamic acid. No polymer was found in the product mixture. The student isolated the two major compounds in the mixture. The mass spectra of these two compounds showed molecular ion (M+) peaks at m / z = 129 and m / z = 258. Suggest structures for these two compounds. [1] [2]OCR 2015<br />
(d) Polymer J has been recently developed by scientists. The repeat unit of polymer J is shown below. 13 CO(CH2)4CONHC(CH3)2CH2O polymer J (i) What are the functional groups in polymer J?[1] (ii) Two different monomers react to form polymer J. Draw the structures of the two monomers in the boxes below. Display the functional groups in each monomer. [2] (iii) Polymer J is used in hair spray. It can be washed away easily with hot water. Suggest why polymer J is able to be washed away easily with hot water.[1] [Total: 20]OCR 2015 Turn over<br />
14 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGEOCR 2015<br />

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F324 Question (i) 3 (a) Answer Mark Scheme Mark (cid:57) (cid:57) NH3 + in second product (cid:57) (ii) perfume/fragrance/flavouring (cid:57) (iii) Reaction 3: (hot) ethanolic ammonia (cid:57) Reaction 4: oxidation (cid:57) Reaction 5: hydrolysis (cid:57) June 2015 Guidance ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous ALLOW ONa+ OR O (cation not required) DO NOT ALLOW ONa (covalent bond) DO NOT ALLOW O (without the sodium) ALLOW delocalised carboxylate IGNORE solvent OR food additive ALLOW NH3 (dissolved) in ethanol IGNORE other conditions ALLOW oxidisation/oxidised DO NOT ALLOW redox ALLOW nucleophilic addition-elimination DO NOT ALLOW nucleophilic substitution IGNORE acid/base 13<br />
F324 Question (b) M1 Compound E Answer Mark Scheme Mark H2C CHO NH2 M2 Compound F H2C M3 Compound G M4 Compound H COOH NH2 CHNH2 COOH CH=CH2 M5 Compound G (cid:51) (cid:51) (cid:51) (cid:51) 14 June 2015 Guidance ANNOTATE ANSWER WITH TICKS AND CROSSES ETC ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous Labels are not required for compound E, F, G or H IGNORE labels for M1, M2, M3 and M4 CH2=CH must be shown in E ALLOW C2H3 OR CHCH2 for CH=CH2 in F ALLOW ECF from error in structure of aldehyde E ALLOW multiple repeat units but must be full repeat units ALLOW end bonds shown asDO NOT ALLOW if structures have no end bonds IGNORE brackets unless they are used to pick out the repeat unit from a polymer chain IGNORE n ALLOW C2H4NO2 for CH(NH2)COOH in polymer G ALLOW C2H3 OR CHCH2 for CH=CH2 in polymer H ALLOW ECF from NH2CH2CH=CHCOOH for the formation of compound G or compound H ALLOW alkene forms addition polymer/polymer with same<br />
F324 Question OR Answer CHNH2 COOH Is an addition polymer (cid:51) M6 Compound H OR CH=CH2 is a condensation polymer (cid:57) (c) (i) Mark Scheme Mark Guidance empirical formula as monomer ALLOW equation for reaction June 2015 ALLOW amino acid forms condensation polymer OR (molecules of) compound F join/bond/add/react/form polymer and water/small molecule ALLOW equation for reaction ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous (cid:51) 15<br />
Answer Mark Scheme Mark June 2015 Guidance ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous ALLOW a cyclic amide with a 3 membered ring ALLOW F324 Question (ii) (cid:57) (cid:51) (d) (i) Ester AND amide (cid:57) OR a structure obtained by condensation of a glutamic acid molecule with the first cyclic amide ALLOW peptide for amide 16<br />
F324 Question (ii) (iii) June 2015 Guidance ALLOW correct structural OR displayed OR skeletal formulae OR a combination of above as long as unambiguous Functional groups do not need to be fully displayed ALLOW structures as shown; the O-H bond and the N-H bonds in the functional groups do not need to be displayed DO NOT ALLOW -COOH ALLOW Penalise incorrect connectivity to OH once in this question ALLOW (the molecule/amide/ester) can form hydrogen/H- bonds with water IGNORE acid/base Answer Mark Scheme Mark (cid:51) (cid:51) (The molecule/amide/ester) can be hydrolysed (cid:57) Total 20 17<br />

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