Benzedrine is a pharmaceutical which stimulates the central nervous system in a similar manner to adrenalin. Benzedrine Adrenalin

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1 1. Adrenalin is a hormone which raises blood pressure, increases the depth of breathing and delays fatigue in muscles, thus allowing people to show great strength under stress. Benzedrine is a pharmaceutical which stimulates the central nervous system in a similar manner to adrenalin. O C C(C ) N O C(O) C N Benzedrine Adrenalin C (a) On the structure for benzedrine mark with a ( * ) any asymmetric carbon atom that causes chirality. Suggest why adrenalin is more soluble in water than is benzedrine (b) Give the structural formulae of the organic products obtained when benzedrine reacts with: an aqueous acid such as dilute hydrochloric acid; ethanoyl chloride in the absence of a catalyst; (iii) excess ethanoyl chloride in the presence of the catalyst anhydrous aluminium chloride. Maltby Academy 1

2 (d) It is possible to eliminate a molecule of water from adrenalin which for the purpose of this question may be represented as R C(O) C 2 N C 3. Draw the structural formulae of the two stereoisomers produced. (e) The mass spectra of both benzedrine and adrenalin have a peak at a mass/charge ratio of 44. Draw the structure of the species which give these peaks. in benzedrine; in adrenalin. (Total 11 marks) 2. Alanine, 2-aminopropanoic acid, is the simplest chiral amino acid found in nature and is optically active. N C C 2 C 3 O O Maltby Academy 2

3 (a) Explain the meaning of the term chiral. ow is optical activity detected experimentally? (iii) If alanine is made from propanoic acid the product mixture does not show optical activity. Explain why this is so. (b) Alanine reacts with both acids and bases. Give the structural formulae of the compounds you would expect if alanine reacts with hydrochloric acid sodium hydroxide Maltby Academy 3

4 (c) Alanine has a high melting temperature of 300 C, much higher than would be expected for the structure given at the start of the question. Draw the structure that is actually present in the solid, and explain why the melting temperature is so high (d) Polyamides are made from a diacid dichloride and a diamine; they are condensation polymers. Explain the term condensation polymer. Suggest the structural formula of a diacid dichloride and a diamine that could be reacted to form a polyamide. Maltby Academy 4

5 (iii) Draw sufficient of the polymer chain that would result from the reaction of the compounds in to make the structure of the polymer clear. (iv) Alanine could be converted to C 3 C(N 2 )COCl which on its own could polymerise to a polyamide. Draw the structure of the polymer chain showing three alanine repeating units and all the bonds in the amide links. (Total 16 marks) 3. A chemist has synthesised a compound W believed to be Cl O O C C C C O Maltby Academy 5

6 (a) State and explain what you would see if W is reacted with: sodium carbonate solution bromine water. (3) (b) W shows both types of stereoisomerism. ow many stereoisomers of W are there? Briefly explain your answer. Explain why W shows optical isomerism. Maltby Academy 6

7 (c) Describe how you would show that W contains chlorine. (5) (Total 14 marks) 4. The optical isomers of alanine, C 3 C(COO)N 2 A B C D have different melting points rotate the plane of plane polarised light in opposite directions react at different rates with ethanoyl chloride, C 3 COCl both occur naturally in protein molecules (Total 1 mark) 5. (a) *C(C 3 ) 1 (the three) O groups allow adrenalin to form more hydrogen bonds with water (than does benzedrine) 2 (b) C C(C )N (Cl ) Can use R in place of C 6 5 C 2 C(C 3 ) in both and Maltby Academy 7

8 C C(C )N C C ( 1) O (iii) C C C C(C ) N C C O O substitution(s) in ring at any position(s) production of amide 2 (d) R NC 3 C C C C R 2 NC 3 (e) (C(C 3 ) N 2 ) + 1 (C 2 N C 3 ) + / (C(O)C 2 ) + max 1 for (e) if no charges shown must show some structure in answers ie. C 2 5 N(0) 1 [11] 6. (a) It is non-superimposable on mirror image/ it has a single asymmetric carbon atom 1 rotates the plane (of polarisation) of (plane ) polarised (monochromatic) light OR Use a polarimeter rotates the plane (of polarisation) of the light 2 (iii) product is an equimolar mixture/racemic mixture so rotations cancel 2 (b) N 3 + Cl on the amino group COO Na + on the carboxyl group 2 (c) Zwifterion s structure There is ionic attraction between adjacent zwitterions 2 Maltby Academy 8

9 (d) (polymer formed by) elimination/ removal of a small molecule/ water (between two monomers) 1 any CIOC***COCl and 2 N*C 2 *N 2 2 (iii) structure consequential on answer to showing amide link and extension of the chain 2 (iv) N C C N C C N C C C O C O C O CON drawn out Show 3 units 2 [16] 7. (a) effervescence COO present/acid/ acidic/contains + [if wrong gas is identified second mark is lost] 2 Accept bubbles, fizzing Reject gas/co2 evolved Reject just acid-base reaction Decolourises OR brown/orange/yellow to colourless Reject clear used instead of colourless compound contains C=C / unsaturated Accept alkene Reject just double bond white precipitate so is a phenol 3 Accept activated benzene ring/o on benzene ring Maltby Academy 9

10 (b) Four (Two) cis/trans (or geometric), and (two) chiral/optical isomers/ enantiomers OR Two cis-trans/geometric isomers Two optical isomers/enantiomers OR 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 having non-superimposable mirror images 2 Reject asymmetric carbon atom/chiral molecule (c) QWC NaO (solution) Accept W identified as secondary halogenoalkane so no NaO needed for first two marks acidify with /add excess NO 3 [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) white precipitate soluble in dilute/aqueous ammonia 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 10

11 8. B [1] Maltby Academy 11

Assessment Schedule 2013 Chemistry: Demonstrate understanding of the properties of organic compounds (91391)

NCEA Level 3 Chemistry (91391) 2013 page 1 of 8 Assessment Schedule 2013 Chemistry: Demonstrate understanding of the properties of organic compounds (91391) Evidence Statement Q Evidence Achievement Achievement