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OCR A Jun 2014 Paper 4 Q1
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![Answer all the questions. 1 Salicylic acid is a naturally occurring carboxylic acid, widely used in organic synthesis. OH COOH salicylic acid (a) The flowchart below shows some reactions of salicylic acid. (i) In the box below, draw the structure of the organic compound formed by reaction 1. [1] OH COOH excess NaOH(aq) reaction 1 salicylic acid Br2 reaction 2 reaction 3 OH Br COOH OH CH(CH3)2OCR 2014<br />
(ii) Describe what would be observed during reaction 2.[1] (iii) Write a chemical equation to represent reaction 2. (iv) State the reagents and conditions in reaction 3.[1] (b) Bromine reacts more readily with salicylic acid than with benzene. [1]OCR 2014 (i) Outline the mechanism for the bromination of salicylic acid shown in reaction 2 in the flowchart. A halogen carrier is not required for this reaction. The electrophile is Br2. [4] Turn over<br />
(ii) Explain why bromine reacts more readily with salicylic acid than with benzene. In your answer, you should use appropriate technical terms, spelled correctly.[3]OCR 2014<br />
(c) Mesalazine is a drug that can be synthesised from salicylic acid in two steps. OH COOH salicylic acid two-step synthesis OH H2N COOH mesalazine (i) Suggest a two-step synthesis to prepare mesalazine from salicylic acid. For each step state the reagents used,write a chemical equation. (ii) Mesalazine reacts with acids to form salts. Explain how mesalazine is able to react with acids.[1] [4]OCR 2014 Turn over<br />
(iii) Mesalazine reacts in another two-stage process as shown below. In the boxes, draw the structures of organic compounds A and B. [2] OH NaNO2 and HCl H2N COOH < 10 C mesalazine compound A NaOH(aq) followed by neutralisation compound B OH OH COOH (d) Salicylic acid can be used to form a condensation polymer similar to Terylene. OH COOH salicylic acid (i) Explain what is meant by the term condensation polymer.[1]OCR 2014<br />
(ii) The repeat unit of Terylene is shown below. C O CH2 CH2 Terylene Draw the skeletal formulae of two monomers that can be used to form Terylene. (iii) Salicylic acid reacts with 3-hydroxypropanoic acid to form a mixture of condensation polymers. To form one polymer, the two monomers react in equal quantities. Draw the repeat unit of this polymer, displaying the link between the monomer units. [2] [1] [Total: 22]OCR 2014 Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_4_QP_JUN14_question_1-0.jpg)
![F324 Question (a) (i) (cid:57) (a) (ii) (Bromine) would be decolourised/turn (from orange/red/yellow/brown) to colourless OR white precipitate/solid/emulsion (formed) (cid:57) (a) (iii) + Br2+ HBr (cid:57) Where circles have been placed round charges, this is for clarity only and does not indicate a requirement Guidance Answer Mark Mark Scheme June 2014 ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous DO NOT ALLOW ONa OR -COO-Na (covalent bond) ALLOW O- ALLOW ONa ALLOW COONa OR ALLOW delocalised carboxylate OR (Na+) IGNORE goes clear DO NOT ALLOW other colours for bromine IGNORE cream precipitate DO NOT ALLOW salicylic acid turns colourless/decolourised IGNORE temperature/fumes ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous MUST be all correct to score mark ALLOW molecular formulae, i.e. C7H6O3 + Br2 (cid:111) C7H5O3Br+ HBr<br />
Answer (CH3)2CHOH/CH3CH(OH)CH3/propan(-)2(-)ol AND acid/H+/H2SO4 (catalyst) (cid:57) F324 Question (a) (iv) (b) (i) Mark Scheme June 2014 Mark Guidance ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous ALLOW 2-propanol DO NOT ACCEPT incorrect name or incorrect formula of alcohol IGNORE reflux/concentrated (acid) ALLOW mechanism with Br+ electrophile (Maximum 3 marks) No Br2 dipole needed Curly arrow to Br from ring OR from within the ring AND curly arrow Br-Br bond to Br (cid:57) IGNORE any equations involving a halogen carrier BUT DO NOT ALLOW intermediate with -system covering less than half of ring: correct intermediate (with charge) curly arrow from CH to reform ring (cid:57) (cid:57) ALLOW + charge anywhere inside the horseshoe Horseshoe must have open end towards Br Apply ecf to error in structure of intermediate (M2)<br />
Question F324 Mark Scheme June 2014 Answer Mark Guidance ALLOW Kekul mechanism as shown (Maximum 3 marks if Br+ is the electrophile) + HBr /H++ Br- (cid:57) (Br - may be shown in the first step) Correct products ALLOW double bonds in alternate arrangement<br />
F324 Question (ii) (b) Mark Scheme June 2014 Answer (In salicylic acid) lone pair/pair of electrons on O(H)/phenol is ~ (partially) delocalised into the ring (cid:57) electron density increases/is high ORA (cid:57) Br2/electrophile is (more) polarised ORA (cid:57) (cid:4) QWC: delocalised/delocalized/delocalise etc. must be spelled correctly in the correct context at least once Mark Guidance ALLOW diagram to show movement of lone pair into ring but delocalised ring must be mentioned ALLOW lone pair/pair of electrons on O(H)/phenol is (partially) drawn/attracted/pulled into delocalised ring IGNORE activates the ring ALLOW more electron rich DO NOT ALLOW charge density or electronegativity ALLOW (salicylic acid) attracts electrophiles more/more susceptible to electrophilic attack ALLOW Br2 is (more) attracted OR Br2 is not polarised by benzene OR induces dipoles (in bromine/electrophile) Delocalise(d) needed to score the first marking point (c) (i) Step 1 Add HNO3 (cid:57) + HNO3 ALLOW reagent mark if HNO3 in equation IGNORE H2SO4 (NOTE: H2SO4 not required with phenols) IGNORE concentrations of acids/temperature ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous Equations MUST be completely correct for one mark each H2O (cid:57)<br />
F324 Question Answer Step 2 Tin AND concentrated HCl (cid:57) + 6 [H] Mark Scheme Mark DO NOT ALLOW 3H2 + 2 H2O June 2014 Guidance DO NOT ALLOW nitrogen/N lone pair accepts hydrogen (proton/H+ required) ALLOW nitrogen donates an electron pair/lone pair to H+ IGNORE NH2 group donates electron pair ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous ALLOW N2Cl OR N2 DO NOT ALLOW NN+ OR NN+ Cl- DO NOT ALLOW N2-Cl (covalent bond) +Cl (cid:57) (c) (ii) Nitrogen electron pair OR nitrogen lone pair accepts a proton/H+ (cid:57) (c) (iii) compound A (cid:57) compound B (cid:57)<br />
F324 Question Answer (d) (d) (i) monomers join/bond/add/react/form polymer/form chain AND another product/small molecule/H2O/HCl (cid:57) (ii) Mark Scheme June 2014 Mark Guidance IGNORE specific reference to number of molecules DO NOT ALLOW HO (penalise connectivity once only) Both structures must be skeletal DO NOT ALLOW stray sticks (skeletal means CH3 attached) DO NOT ALLOW structure with a C shown, e.g. (cid:57) (cid:57) Connectivity is penalised only in this question ALLOW (d) (iii) (cid:57) ester link MUST be fully displayed OR ALLOW correct structural OR displayed OR skeletal formulae OR combination of above as long as unambiguous<br />
F324 Question Answer Mark Scheme Mark ALLOW June 2014 Guidance IGNORE bond angles DO NOT ALLOW more than one repeat unit unless correct repeat unit is indicated IGNORE brackets with n ALLOW any correct repeat unit ALLOW end bonds shown as - - - - - DO NOT ALLOW if structure has no end bonds Total 22<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_4_QP_JUN14_answer_1-0.jpg)
