Name this organic reagent and state the conditions for the preparation. Reagent... Conditions (3)

Transcription

1 1. (a) Propanoic acid, C 3 C 2 COO, can be prepared from carbon dioxide and an organic reagent. Name this organic reagent and state the conditions for the preparation. Reagent... Conditions (3) (b) Describe what you would see and write the equations for the reactions of propanoic acid with: (i) a solution of sodium carbonate Observation... Equation... solid phosphorus pentachloride. Observation... Equation... (c) Propanoic acid can also be prepared from propanal, C 3 C 2 CO. State the reagents for this conversion. Reagents... Maltby Academy 1

2 (d) 1-aminobutan-2-ol, C 3 C 2 C(O)C 2 N 2, is an active ingredient in some deodorant sprays. It can be prepared from propanal by the following two-step process. Step Step C 3 C C 3 C 2 C(O ) C N C 3 C 2 C(O)C 2 N 2 (i) For Step 1 State the reagents and conditions... Name the type of reaction.. (3) For Step 2 State the reagents and conditions... Name the type of reaction.. (3) Maltby Academy 2

3 (e) Write the structural formula of the organic product formed when 1-aminobutan-2-ol reacts with: (i) ethanoyl chloride, C 3 COCl hydrochloric acid. (1) (f) 1-aminobutan-2-ol exists as two isomers with the same structural formula. Identify the type of isomerism and draw the TWO isomers, showing clearly the difference between them. Type of isomerism... (3) (Total 21 marks) Maltby Academy 3

4 2. Methanoic acid and ethanol react together to form ethyl methanoate, COOC 2 5, and water. This reaction is reversible and can be allowed to reach equilibrium. COO(l) + C 2 5 O(l) COOC 2 5 (l) + 2 O(l) Δ = +45 kj mol 1 (a) Draw the full structural formula of ethyl methanoate, showing all bonds. (1) (b) What type of organic compound is ethyl methanoate?... (1) (c) In an experiment, 3.00 mol methanoic acid, COO, and 6.25 mol ethanol, C 2 5 O, were mixed together. A small quantity of catalyst was added. The mixture was left for several days in a water bath to reach equilibrium at constant temperature. (i) Complete the table. at start of experiment Number of moles in the reaction mixture COO C 2 5 O COOC O at equilibrium 0.50 Maltby Academy 4

5 Write an expression for the equilibrium constant, K c, for the reaction. (1) (iii) Calculate K c for the reaction at the temperature of the experiment. The total volume of the equilibrium mixture was 485 cm 3. (iv) State and explain whether K c for this reaction has units. (1) Maltby Academy 5

6 (d) (i) The temperature of this equilibrium mixture is lowered. Explain the effect of this on the value of the equilibrium constant and hence on the yield of ethyl methanoate. (4) A student added more catalyst to the mixture. State, giving a reason, what would happen to the composition of the equilibrium mixture. (1) (Total 13 marks) 3. A chemist has synthesised a compound W believed to be Cl O O C C C C O Maltby Academy 6

7 (a) State and explain what you would see if W is reacted with: (i) sodium carbonate solution bromine water. (3) (b) W shows both types of stereoisomerism. (i) ow many stereoisomers of W are there? Briefly explain your answer. Explain why W shows optical isomerism. Maltby Academy 7

8 (c) Describe how you would show that W contains chlorine (5) (Total 14 marks) 4. (a) Ethylmagnesium bromide of formula, or any other halide NOT C 2 5 BrMg, (1) Dry ether / ethoxyethane Followed by hydrolysis / acid / water (1) Grignard reagent / named reagent with incorrect alkyl group scores (0) for (1) reagent but can score both condition marks. If halogenoalkane given as reagent, can score 1 st mark if Mg included under 3 conditions. (b) (i) Observation effervescence/ bubbles/ fizzing (1) NOT gas evolved 2C 2 5 COO + Na 2 CO 3 2C 2 5 COONa + CO O (1) 2 Observation steamy/ misty/ white fumes (1) NOT smoke C 2 5 COO + PCl 5 C 2 5 COCl + POCl 3 + Cl (1) 2 Maltby Academy 8

9 (c) Reagents potassium dichromate ((VI)) / K 2 Cr 2 O 7, (1) sulphuric acid / 2 SO 4 / hydrochloric acid / Cl but conseq. on an oxidising (1) agent ALLOW acidified potassium dichromate / + and Cr 2 O 7 2 ALLOW acidified dichromate ions Acidified dichromate (without ion) scores just (1) ACCEPT Potassium manganate(vii) / potassium permanganate / KMnO 4 / Tollens * / Fehling s* (1) Acidified / alkaline* / neutral (1) 2 (*) need to acidify to liberate free acid for 2 nd mark (d) (i) Reagent Condition (any one of) (to match) CN and KCN CN or KCN (buffered between) p between 6 and 9 KCN + acid / + NOT excess CN + base / O NOT excess Type of reaction Nucleophilic addition - both words needed (1) 3 Reagent Condition (any one of) (to match) ydrogen Pt / Ni / Pd (catalyst) IGNE ref to temp. Sodium (in) ethanol Lithium aluminium hydride dry ether / ethoxyethane Sodium borohydride (in) aqueous / water / ethanol / methanol Type of reaction Reduction ACCEPT redox / hydrogenation (not addition) ACCEPT nucleophilic addition if metal hydrides used (1) 3 Maltby Academy 9

10 (e) (i) 2 NOT 1 Maltby Academy 10

11 (f) Optical NOT stereo (1) ALLOW C 2 5 for C 2 C 3 MUST show the two as object and mirror image but NOT C must not be bonded to in O group Near-miss molecule plus mirror image (1) 3 The two solid lines in 3D structure must not be at 180 [21] 5. (a) O C O C C 1 (b) ester 1 (c) (i) Moles: C 2 5 O: 3.75 (1) Moles: COOC 2 5 : 2.50 and moles 2 O : 2.50 (1) for both 2 [COOC 2 5 ][ 2O] K c 1 [COO][C O] 2 5 Reject obviously round brackets ( ) Maltby Academy 11

12 (iii) K c (1) Must have clearly divided moles of each component by for 1 st mark e.g. [COOC 2 5 ] = [ 2 O] = 5.16 (mol dm 3 ) and [COO] = 1.03 (mol dm 3 ) and [C 2 5 O] = 7.73 (mol dm 3 ) = 3.33 (1) stand alone mark IGNE sig.figs. 2 2 (2.50) Accept K c = 3.33 only scores if it is stated that V cancels either here or in (iv) If [ 2 O] omitted in, then answer K c = mol 1 dm 3 but this will give K c = 1.33 mol 1 dm 3 with V omitted from calculation (1) Reject 1 st mark if 485 used as V in expression (iv) No, (as) equal numbers of moles on both sides volumes cancel mol dm 3 cancel units cancel crossing out units to show they cancel 1 Accept equal powers/moles on both sides powers cancel Mark CQ on K c expression in Reject concentrations cancel (d) (i) (as reaction) endothermic (1) Accept exothermic in backward direction (or words to that effect) K c decreases (1) If state exothermic in forward direction, 1 mark only (out of 4) for CQ increase in K c numerator in quotient (has to) decrease denominator in quotient (has to) increase fraction (has to) decrease (1) yield of COOC 2 5 decreases (1) 4 Maltby Academy 12

13 no effect as catalysts do not affect (the value of) K no effect as catalysts do not affect the position of equilibrium no effect as catalysts do not affect the yield No effect as catalysts increase the rate of the forward and backward reactions equally/to the same extent no effect as catalysts only increase the rate no effect as catalysts only alter the rate no effect can be stated or implied IGNE any references to activation energy 1 Reject just catalysts increase rate [13] 6. (a) (i) effervescence (1) COO present/acid/ acidic/contains + (1) [if wrong gas is identified second mark is lost] 2 Accept bubbles, fizzing Reject gas/co2 evolved Reject just acid-base reaction Decolourises (1) brown/orange/yellow to colourless Reject clear used instead of colourless compound contains C=C / unsaturated (1) Accept alkene Reject just double bond white precipitate so is a phenol (1) 3 Accept activated benzene ring/o on benzene ring Maltby Academy 13

14 (b) (i) Four (1) (Two) cis/trans (or geometric), and (two) chiral/optical isomers/ enantiomers (1) Two cis-trans/geometric isomers (1) Two optical isomers/enantiomers (1) cis-trans/geometric isomers and optical isomers/enantiomers (1 only) 2 Accept correct description of the idea of cis-trans or optical isomerism without the name Reject rotates plane of plane-polarised light Molecule has a chiral centre/chiral carbon/carbon with four different groups (1) having non-superimposable mirror images (1) 2 Reject asymmetric carbon atom/chiral molecule (c) QWC NaO (solution) (1) Accept W identified as secondary halogenoalkane (1) so no NaO needed (1) for first two marks acidify with /add excess NO 3 (1) [If Cl is added here, only the NaO mark can score] Accept neutralise with nitric acid Reject just add NO 3 add silver nitrate (solution) (1) white precipitate (1) soluble in dilute/aqueous ammonia (1) Accept dilute and concentrated ammonia Reject concentrated ammonia alone If no NaO max (4) If NO 3 added only before NaO, or no acid is added at all, then can score 3 rd, 4 th and 5 th marks If order of addition is NaO, AgNO 3, NO 3 can score (5) If no NaO and no NO3, can score last 3 marks If any reagent other than silver nitrate, including ammoniacal silver nitrate, is used only the 1 st and 2 nd marks can score 5 [14] Maltby Academy 14