... (1) Explain the origin of the interaction represented by the dotted lines in the figure above

Transcription

1 The following figure shows a simplified representation of the arrangement of some amino acids in a portion of a protein structure in the form of an α-helix. (a) Name the type of protein structure in the figure. () (b) Explain the origin of the interaction represented by the dotted lines in the figure above. (4) (Total 5 marks) Page of 76

2 2 The tripeptide shown in the following figure is formed from the amino acids glycine, threonine and lysine. (a) (b) Draw a separate circle around each of the asymmetric carbon atoms in the tripeptide in the figure. Draw the zwitterion of glycine. () (c) Draw the structure of the species formed when glycine reacts with an excess of bromomethane. () (d) Deduce the IUPAC name of threonine. () () Page 2 of 76

3 (e) Draw the structure of the species formed by lysine at low ph. () (Total 5 marks) 3 The anticancer drug cisplatin operates by reacting with the guanine in DNA. Figure shows a small part of a single strand of DNA. Some lone pairs are shown. Figure (a) The DNA chain continues with bonds at X and Y. State the name of the sugar molecule that is attached to the bond at X. () Page 3 of 76

4 (b) Messenger RNA is synthesised in cells in order to transfer information from DNA. The bases in one strand of DNA pair up with the bases used to synthesise RNA. Figure 2 shows two bases used in RNA. Figure 2 Suggest which of the bases A and B forms a pair with guanine in Figure when messenger RNA is synthesised. Explain how the base that you have chosen forms a base pair with guanine. (4) (c) Cisplatin works because one of the atoms on guanine can form a co-ordinate bond with platinum, replacing one of the ammonia or chloride ligands. Another atom on another guanine can also form a co-ordinate bond with the same platinum by replacing another ligand. On Figure, draw a ring round an atom in guanine that is likely to bond to platinum. () Page 4 of 76

5 (d) An adverse effect of cisplatin is that it also prevents normal healthy cells from replicating. Suggest one way in which cisplatin can be administered so that this side effect is minimised. () (Total 7 marks) 4 A peptide is hydrolysed to form a solution containing a mixture of amino acids. This mixture is then analysed by silica gel thin-layer chromatography (TLC) using a toxic solvent. The individual amino acids are identified from their R f values. Part of the practical procedure is given below.. Wearing plastic gloves to hold a TLC plate, draw a pencil line.5 cm from the bottom of the plate. 2. Use a capillary tube to apply a very small drop of the solution of amino acids to the mid-point of the pencil line. 3. Allow the spot to dry completely. 4. In the developing tank, add the developing solvent to a depth of not more than cm. 5. Place your TLC plate in the developing tank. 6. Allow the developing solvent to rise up the plate to the top. 7. Remove the plate and quickly mark the position of the solvent front with a pencil. 8. Allow the plate to dry in a fume cupboard. (a) Parts of the procedure are in bold text. For each of these parts, consider whether it is essential and justify your answer. (4) Page 5 of 76

6 (b) Outline the steps needed to locate the positions of the amino acids on the TLC plate and to determine their R f values. (4) (c) Explain why different amino acids have different R f values. (2) (Total 0 marks) 5 A drug is designed to simulate one of the following molecules that adsorbs onto the active site of an enzyme. Which molecule requires the design of an optically active drug? A B C D (Total mark) Page 6 of 76

7 6 (a) The structures and common names of two amino acids are shown. Draw the structure of the zwitterion of proline. Draw the structure of the tripeptide formed when a proline molecule bonds to two alanine molecules, one on each side. () (2) (b) Sections of two polymers, L and M, are shown. Give the IUPAC name of a monomer that forms polymer L... () Give the IUPAC name of the monomer that forms polymer M... () Page 7 of 76

8 (iii) (vi) Draw the section of a polymer made from a dicarboxylic acid and a diamine that is isomeric with the section of polymer M shown. Explain why polymer L is non-biodegradable..... ().. () (Total 7 marks) 7 Lysine and alanine are two amino acids. lysine alanine (a) Give the IUPAC name of lysine. () (b) Draw structures to show the product formed in each case when lysine reacts with an excess of aqueous HCl () an excess of aqueous NaOH () Page 8 of 76

9 (iii) methanol in the presence of a small amount of concentrated H 2 SO 4 () (c) The mass spectrum of alanine gives a major peak at m / z = 44 Write an equation for the fragmentation of the molecular ion of alanine to give an ion that produces this peak. In your answer, draw the displayed formula for this fragment ion. (2) (d) Draw a dipeptide formed from one molecule of lysine and one molecule of alanine. () (e) The dipeptide in part (d) is hydrolysed in acid conditions and the mixture produced is analysed by column chromatography. The column is packed with a resin which acts as a polar stationary phase. Suggest why lysine leaves the column after alanine. (2) (Total 9 marks) Page 9 of 76

10 8 Alanine and aspartic acid are naturally occurring amino acids. (a) Draw the structure of the zwitterion formed by alanine. () (b) Draw the structure of the compound formed when alanine reacts with methanol in the presence of a small amount of concentrated sulfuric acid. () (c) Draw the structure of the species formed by aspartic acid at high ph. () (d) Draw the structure of a dipeptide formed by two aspartic acid molecules. () (Total 4 marks) Page 0 of 76

11 9 (a) The tripeptide shown is formed from the amino acids alanine, threonine and lysine. Draw a separate circle around each of the asymmetric carbon atoms in the tripeptide. Draw the zwitterion of alanine. () (iii) (iv) Give the IUPAC name of threonine... Draw the species formed by lysine at low ph. () () () (b) The repeating unit shown represents a polyester. Name this type of polymer... () Give the IUPAC name for the alcohol used to prepare this polyester... () Page of 76

12 (c) The repeating unit shown represents a polyalkene co-polymer. This co-polymer is made from two different alkene monomers. Name the type of polymerisation occurring in the formation of this co-polymer... () Draw the structure of each alkene monomer. Alkene monomer Alkene monomer 2 (2) (d) One of the three compounds shown in parts (a), (b) and (c) cannot be broken down by hydrolysis. Write the letter (a), (b) or (c) to identify this compound and explain why hydrolysis of this compound does not occur. Compound... Explanation... (2) (Total marks) Page 2 of 76

13 0 A possible synthesis of the amino acid X is shown below. (a) Name and outline a mechanism for Step. Name of mechanism... Mechanism (5) (b) Give the IUPAC name of the product of Step 2. () (c) For Step 3, give the reagent, give a necessary condition and name the mechanism. Reagent... Condition... Name of mechanism... (3) Page 3 of 76

14 (d) At room temperature, the amino acid X exists as a solid. Draw the structure of the species present in the solid amino acid. () With reference to your answer to part (d), explain why the melting point of the amino acid X is higher than the melting point of CH 3 CH 2 CH(OH)COOH (Extra space)..... (2) (e) There are many structural isomers of X, CH 3 CH 2 CH(NH 2 )COOH. Draw a structural isomer of X that is an ethyl ester. () Draw a structural isomer of X that is an amide and also a tertiary alcohol. () Page 4 of 76

15 (iii) Draw a structural isomer of X that has an unbranched carbon chain and can be polymerised to form a polyamide. () (f) Draw the structure of the tertiary amine formed when X reacts with bromomethane. () (Total 6 marks) Page 5 of 76

16 The amino acids aspartic acid and phenylalanine react together to form a dipeptide. This dipeptide can be converted into a methyl ester called aspartame. Aspartame has a sweet taste and is used in soft drinks and in sugar-free foods for people with diabetes. Hydrolysis of aspartame forms methanol initially. After a longer time the peptide link breaks to form the free amino acids. Neither of these amino acids tastes sweet. (a) Apart from the release of methanol, suggest why aspartame is not used to sweeten foods that are to be cooked. (Extra space)... () (b) Give the IUPAC name of aspartic acid. () (c) Draw the organic species formed by aspartic acid at high ph. () Page 6 of 76

17 (d) Draw the zwitterion of phenylalanine. () (e) Phenylalanine exists as a pair of stereoisomers. State the meaning of the term stereoisomers (2) Explain how a pair of stereoisomers can be distinguished (Extra space)..... (2) (Total 8 marks) Page 7 of 76

18 2 The amide or peptide link is found in synthetic polyamides and also in naturally occurring proteins. (a) Draw the repeating unit of the polyamide formed by the reaction of propanedioic acid with hexane-,6-diamine. (2) In terms of the intermolecular forces between the polymer chains, explain why polyamides can be made into fibres suitable for use in sewing and weaving, whereas polyalkenes usually produce fibres that are too weak for this purpose. (Extra space)... (3) Page 8 of 76

19 (b) Name and outline a mechanism for the reaction of CH 3 CH 2 COCl with CH 3 NH 2 Name of mechanism... Mechanism (5) Give the name of the product containing an amide linkage that is formed in the reaction in part (b). () (c) The dipeptide shown below is formed from two different amino acids. Draw the structure of the alternative dipeptide that could be formed by these two amino acids. () Page 9 of 76

20 (d) The amino acids serine and aspartic acid are shown below. Give the IUPAC name of serine. () Draw the structure of the species formed when aspartic acid reacts with aqueous sodium hydroxide. () (iii) Draw the structure of the species formed when serine reacts with dilute hydrochloric acid. () (iv) Draw the structure of the species formed when serine reacts with an excess of bromomethane. () (Total 6 marks) Page 20 of 76

21 3 (a) Name compound Y, HOCH 2 CH 2 COOH... () (b) Under suitable conditions, molecules of Y can react with each other to form a polymer. Draw a section of the polymer showing two repeating units. () Name the type of polymerisation involved. () (c) When Y is heated, an elimination reaction occurs in which one molecule of Y loses one molecule of water. The organic product formed by this reaction has an absorption at 637 cm in its infrared spectrum. Identify the bond that causes the absorption at 637 cm in its infrared spectrum. () Write the displayed formula for the organic product of this elimination reaction. () (iii) The organic product from part can also be polymerised. Draw the repeating unit of the polymer formed from this organic product. () Page 2 of 76

22 (d) At room temperature, 2-aminobutanoic acid exists as a solid. Draw the structure of the species present in the solid form. () (e) The amino acid, glutamic acid, is shown below. Draw the structure of the organic species formed when glutamic acid reacts with each of the following. an excess of sodium hydroxide () an excess of methanol in the presence of concentrated sulfuric acid () (iii) ethanoyl chloride () Page 22 of 76

23 (f) A tripeptide was heated with hydrochloric acid and a mixture of amino acids was formed. This mixture was separated by column chromatography. Outline briefly why chromatography is able to separate a mixture of compounds. Practical details are not required (3) (Total 3 marks) 4 (a) Consider the tripeptide shown below that is formed from three amino acids, K, L and M. Name the process by which the tripeptide is split into three amino acids. () Give the IUPAC name for the amino acid K. () (iii) Draw the structure of the zwitterion of amino acid L. () Page 23 of 76

24 (iv) Draw the structure of the species formed by amino acid M at low ph. () (b) Consider the amino acid serine. Draw the structure of the product formed when serine reacts with an excess of CH 3 Br () Draw the structure of the dipeptide formed by two molecules of serine. () (Total 6 marks) Page 24 of 76

25 5 The three amino acids shown below were obtained by hydrolysis of a protein. (a) Draw the zwitterion of alanine. () Draw the species formed when valine is dissolved in an alkaline solution. () (iii) Draw the species formed by lysine at low ph. () (b) Draw the two dipeptides formed by the reaction of alanine with valine. (2) Page 25 of 76

26 (c) Name a suitable method by which the mixture of amino acids formed by hydrolysis of the protein can be separated.... () (Total 6 marks) 6 The complex cisplatin acts as an anticancer drug by changing the properties of DNA when it reacts with guanine, a component of DNA. When cisplatin is absorbed into the human body, it undergoes a ligand substitution reaction and one chloride ligand is replaced by a water molecule forming a complex ion Q. (a) Write an equation for this substitution reaction to form the complex ion Q.... (2) (b) The complex ion Q can bond to guanine in two different ways. The first way involves a hydrogen atom, from one of the ammonia ligands on Q, bonding to an atom in a guanine molecule. State the type of bond formed to guanine and identify an atom in guanine that could form a bond to this hydrogen atom. Type of bond... Atom in guanine... (2) Page 26 of 76

27 The second way involves a ligand substitution reaction in which an atom in a guanine molecule bonds to platinum by displacing the water molecule from Q. State the type of bond formed between guanine and platinum when a water molecule is displaced and identify an atom in guanine that could bond to platinum in this way. Type of bond... Atom in guanine... (2) (c) State and explain one risk associated with the use of cisplatin as an anticancer drug. Risk Explanation... (2) (Total 8 marks) 7 Fibres are made from natural and from synthetic polymers. Both types of polymer have advantages and disadvantages. (a) Amino acids are the building blocks of naturally-occurring polymers called proteins. Consider the following amino acid. Draw the structure of the amino acid species present in a solution at ph 2. Use your understanding of amino acid chemistry to deduce the structure of the dipeptide formed from two molecules of this amino acid and illustrate your answer with a sketch showing the structure of the dipeptide. Page 27 of 76

28 (iii) Protein chains are often arranged in the shape of a helix. Name the type of interaction that is responsible for holding the protein chain in this shape. (3) (b) Alkenes are the building blocks of synthetic addition polymers. Consider the hydrocarbon G, (CH 3 ) 2 C=CHCH 3, which can be polymerised. Draw the repeating unit of the polymer. Draw the structure of an isomer of G which shows E-Z isomerism. (iii) Draw the structure of an isomer of G which does not react with bromine water. (3) (c) Draw the repeating unit of the polymer formed by the reaction between butanedioic acid and hexane-,6-diamine. (2) Page 28 of 76

29 (d) Two plastic objects were manufactured, one from the polyalkene represented by the repeating unit in part (b) and the other from the polyamide represented by the repeating unit in part (c). After use it was suggested that both objects be disposed of as landfill. Describe an experiment in which you could compare the biodegradability of these two objects. (3) Describe an advantage or a disadvantage of a different method of disposal of such objects compared with landfill. (3) (Total 4 marks) Page 29 of 76

30 8 (a) The repeating units of two polymers, P and Q, are shown below. Draw the structure of the monomer used to form polymer P. Name the type of polymerisation involved. Structure of monomer Type of polymerisation... Draw the structures of two compounds which react together to form polymer Q. Name these two compounds and name the type of polymerisation involved. Structure of compound Name of compound... Structure of compound 2 Name of compound 2... Type of polymerisation... (iii) Identify a compound which, in aqueous solution, will break down polymer Q but not polymer P. (8) Page 30 of 76

31 (b) Draw the structures of the two dipeptides which can form when one of the amino acids shown below reacts with the other. Structure Structure 2 (2) (c) Propylamine, CH 3 CH 2 CH 2 NH 2, can be formed either by nucleophilic substitution or by reduction. Draw the structure of a compound which can undergo nucleophilic substitution to form propylamine. Draw the structure of the nitrile which can be reduced to form propylamine. (iii) State and explain which of the two routes to propylamine, by nucleophilic substitution or by reduction, gives the less pure product. Draw the structure of a compound formed as an impurity. Route giving the less pure product... Explanation... Structure of an impurity (5) (Total 5 marks) Page 3 of 76

32 9 (a) The structure below shows the repeating unit of a polymer. By considering the functional group formed during polymerisation, name this type of polymer and the type of polymerisation involved in its formation. Type of polymer... Type of polymerisation... (2) (b) Draw the structure of the species present in solid aminoethanoic acid, H 2 NCH 2 COOH () (c) Explain why the melting point of aminoethanoic acid is much higher than that of hydroxyethanoic acid, HOCH 2 COOH (2) (Total 5 marks) Page 32 of 76

33 20 Consider the reaction sequence shown below. (a) Name and outline a mechanism for the reaction in Step. Name of mechanism... Mechanism (5) Page 33 of 76

34 (b) Name compound Q formed in Step 2. Two stereoisomers are formed by the dehydration of Q. Give the structures of these two isomers and name the type of stereoisomerism shown. Structures of isomers Type of stereoisomerism... (4) (c) An isomer of Q which has the structure shown below is polymerised to form the biodegradeable polymer known as PHB. Draw the repeating unit of the polymer PHB. Suggest a reason why the polymer is biodegradeable. (2) Page 34 of 76

35 (d) The amino acid R is shown below. Draw the structure of the zwitterion formed by R. Draw the structure of the major organic product formed when an excess of R is reacted with bromomethane. (iii) Name the mechanism of the reaction which results in the formation of the product given in part. (3) (Total 4 marks) Page 35 of 76

36 2 (a) The compound H 2 C=CHCN is used in the formation of acrylic polymers. Draw the repeating unit of the polymer formed from this compound. Name the type of polymerisation involved in the formation of this polymer. (2) (b) When the dipeptide shown below is heated under acidic conditions, a single amino acid is produced. Name this amino acid. Draw the structure of the amino acid species present in the acidic solution. (2) (c) The repeating unit of a polyester is shown below. Deduce the empirical formula of the repeating unit of this polyester. Page 36 of 76

37 Draw the structure of the acid which could be used in the preparation of this polyester and give the name of this acid. Structure... Name... (iii) Give one reason why the polyester is biodegradable. (4) (Total 8 marks) 22 (a) Consider the following amino acid. Draw the structure of the amino acid species present in a solution at ph 2. Draw the structure of the dipeptide formed from two molecules of this amino acid. Page 37 of 76

38 (iii) Protein chains are often arranged in the shape of a helix. Name the type of interaction that is responsible for holding the protein chain in this shape. (3) (b) Consider the hydrocarbon G, (CH 3 ) 2 C=CHCH 3, which can be polymerised. Name the type of polymerisation involved and draw the repeating unit of the polymer. Type of polymerisation... Repeating unit Draw the structure of an isomer of G which shows geometrical isomerism. (iii) Draw the structure of an isomer of G which does not react with bromine water. (4) (Total 7 marks) Page 38 of 76

39 23 The structures of the amino acids alanine and glycine are shown below. (a) Give the systematic name for alanine.... () (b) Alanine exists as a pair of stereoisomers. Explain the meaning of the term stereoisomers. State how you could distinguish between the stereoisomers. (4) (c) Give the structural formula of the species formed by glycine at ph 4. () Page 39 of 76

40 (d) When two amino acids react together, a dipeptide is formed. Give the structural formulae of the two dipeptides which are formed when alanine and glycine react together. Dipeptide Dipeptide 2 (2) (e) Give the structural formula of the organic compound formed when glycine reacts with methanol in the presence of a small amount of concentrated sulphuric acid. () (Total 9 marks) Page 40 of 76

41 24 Three sections of the proton n.m.r. spectrum of CH 3 CHClCOOH are shown below. (a) Name the compound CH 3 CHClCOOH... () (b) Explain the splitting patterns in the peaks at δ.72 and δ (2) (c) Predict the splitting pattern that would be seen in the proton n.m.r. spectrum of the isomeric compound ClCH 2 CH 2 COOH () Page 4 of 76

42 (d) The amino acid alanine is formed by the reaction of CH 3 CHClCOOH with an excess of ammonia. The mechanism is nucleophilic substitution. Outline this mechanism, showing clearly the structure of alanine. (5) (e) The amino acid lysine has the structure Draw structures to show the product formed in each case when lysine reacts with an excess of aqueous HCl, an excess of aqueous NaOH, Page 42 of 76

43 (iii) another molecule of lysine. (3) (Total 2 marks) 25 (a) Synthetic polyamides are produced by the reaction of dicarboxylic acids with compounds such as H 2 N(CH 2 ) 6 NH 2 Name the compound H 2 N(CH 2 ) 6 NH 2 Give the repeating unit in the polyamide nylon 6,6. (2) (b) Synthetic polyamides have structures similar to those found in proteins. Draw the structure of 2-aminopropanoic acid. Draw the organic product formed by the condensation of two molecules of 2-aminopropanoic acid. (2) Page 43 of 76

44 (c) Compounds like H 2 N(CH 2 ) 6 NH 2 are also used to make ionic compounds such as X, shown below. X belongs to the same type of compound as (CH 3 ) 4 N + Br Name this type of compound. State a reagent which could produce X from H 2 N(CH 2 ) 6 NH 2 and give a necessary condition to ensure that X is the major product. Reagent... Condition... (iii) Name the mechanism involved in this reaction to form X. (4) (Total 8 marks) Page 44 of 76

45 Mark schemes (a) Secondary (b) Nitrogen and oxygen are very electronegative Therefore, C=O and N H are polar Which results in the formation of a hydrogen bond between O and H In which a lone pair of electrons on an oxygen atom is strongly attracted to the δ+h [5] 2 (a) (b) (c) Allow (d) 2-amino-3-hydroxybutanoic acid Page 45 of 76

46 (e) [5] 3 (a) 2-deoxyribose (b) Base A If Base B stated, allow mark only for response including hydrogen bonding Top N H forms hydrogen bonds to lone pair on O of guanine The lone pair of electrons on N bonds to H N of guanine A lone pair of electrons on O bonds to lower H N of guanine Allow all 4 marks for a correct diagram showing the hydrogen bonding Students could also answer this question using labels on the diagram (c) Allow either of the nitrogen atoms with a lone pair NOT involved in bonding to cytosine (d) Use in very small amounts / target the application to the tumour [7] 4 (a) Wear plastic gloves: Essential to prevent contamination from the hands to the plate Add developing solvent to a depth of not more than cm 3 : Essential if the solvent is too deep it will dissolve the mixture from the plate Allow the solvent to rise up the plate to the top: Not essential the R f value can be calculated if the solvent front does not reach the top of the plate Page 46 of 76

47 Allow the plate to dry in a fume cupboard: (b) (c) Essential the solvent is toxic Allow hazardous Spray with developing agent or use UV Measure distances from initial pencil line to the spots (x) Measure distance from initial pencil line to solvent front line (y) R f value = x / y Amino acids have different polarities Therefore, have different retention on the stationary phase or different solubility in the developing solvent [0] 5 C [] Page 47 of 76

48 6 (a) Allow CO - 2 and NH + 2 NOTE Two marks for this clip M for alanine section bonded through N M2 for alanine section bonded through C But penalise error in proline ring Allow MAX for correct tripeptide in polymer structure (b) 3-methylpent-2-ene Ignore E-Z, commas, spaces or missing hyphens (iii) 4-amino-3-methylbutanoic acid Ignore commas, spaces or missing hyphens or any polyamide section containing 8 carbons plus two C=O plus two N-H, such as Trailing bonds are required Page 48 of 76

49 (iv) Non polar OR no polar groups / bonds (for attack by water / acids / alkalis / nucleophiles or for hydrolysis) C-C bonds are strong [7] 7 (a) 2,6-diaminohexanoic acid Ignore additional, or or spaces. (b) NB both N must be protonated. Allow NH 3 + allow CO 2 H Allow + H 3 N. Penalise C 4 H 8 here. Allow CO 2. Allow H 2 N. Allow COONa but penalise O Na bond shown. (iii) Allow CO 2 CH 3. Allow NH 3 + or H 2 N. Page 49 of 76

50 (c) for displayed formula of fragment ion. for molecular ion of alanine AND radical. Allow molecular ion without brackets and fragment ion in brackets with outside +. Allow dot anywhere on radical. Allow [C 3 H 7 NO 2 ] for molecular ion. 2 (d) OR OR Dipeptide, not repeating unit /. Allow CO 2 H Allow H 2 N. Allow CONH. (e) M In acid lysine has double positive or more positive charge M2 (Lysine ion) has greater affinity / greater attraction / adheres better / sticks better to polar / stationary phase M2 only scores after a correct M. Ignore greater retention time. [9] Page 50 of 76

51 8 (a) Allow NH 3 + and + NH 3 (b) Allow protonated form, i.e. NH 3 + or + NH 3 (c) Allow CO 2 (d) Allow zwitterion with any COO Allow use of wrong COOH [4] Page 5 of 76

52 Allow NH 3 + and + NH 3 Allow NH 3 + and + NH 3 9 (a) These four only (iii) 2-amino-3-hydroxybutanoic acid Ignore in butan--oic acid Do not penalise commas or missing hyphens Penalise other numbers (iv) (b) Condensation Allow polyester propane-,3-diol Must have e Allow,3-propanediol Page 52 of 76

53 Allow bond to F in CF 3 (c) Addition Not additional Allow monomers drawn either way round OR (d) c for each structure within each pair If wrong, CE = 0 C-C or C-F bonds too strong [] Page 53 of 76

54 Don t penalize position of + on NH 3 0 (a) allow :CN M2 not allowed independent of M, but allow M for correct attack on C+ + rather than δ+ on C=O loses M2 M3 is for correct structure including minus sign but lone pair is part of M4 (b) Allow C 2 H 5 M and M4 for lp and curly arrow 2-bromobutanenitrile Allow 2-bromobutane--nitrile (c) M ammonia or NH 3 Ignore temp or pressure M2 excess (ammonia) excess tied to NH 3 and may score in M unless contradicted Ignore concentrated or sealed container, Acid loses conditions mark M3 nucleophilic substitution Allow close spelling (d) Allow C 2 H 5 Allow CO 2 Allow + NH 3 Page 54 of 76

55 M electrostatic forces between ions in X QOL Allow ionic bonding. Marks independent M2 (stronger than) hydrogen bonding between CH 3 CH 2 CH(OH)COOH CE mention of molecules of X or inter molecular forces between X loses both marks (e) OR Isomer of C 4 H 9 NO 2 Allow NH 2 Isomer of C 4 H 9 NO 2 allow NH 2 Allow (iii) H 2 N CH 2 CH 2 CH 2 COOH or H 2 N (CH 2 ) 3 COOH Isomer of C 4 H 9 NO 2 allow NH 2 OR Do not allow C 3 H 6 - Beware do not credit X itself Page 55 of 76

56 don t penalize position of + on NH 3 (f) Answer has 6 carbons so NOT isomer of X Allow C 2 H 5 Must have bond from C to N not to methyl group [6] (a) (b) (c) Heating speeds up (hydrolysis / breaking of peptide bonds) OR forms non-sweet (amino acids) (2-)aminobutanedioic acid OR 2 not necessary but penalise other numbers at start (2-)aminobutane(-,4-)dioic acid,4 not necessary but penalise other numbers and,4 must be in correct place (QoL) (d) allow CO 2 allow NH 2 allow CO 2 allow +NH 3 Page 56 of 76

57 (e) M Compounds/molecules with same structural formula Not just structure M2 But with bonds/atoms/groups arranged differently in space or in 3D Allow with different spatial arrangement of atom/bond/group Independent marks (Plane) polarised light Rotated in opposite directions Not bent or turned or twisted; not different directions (QoL) [8] 2 (a) Allow CONH- or - COHN - Mark two halves separately lose each for missing trailing bonds at one or both ends or error in peptide link or either or both of H or OH on ends Not allow (C 6 H 2 ) Ignore n M in polyamides - H bonding M2 in polyalkenes - van der Waals forces Penalise forces between atoms or van der Waals bonds M3 Stronger forces (of attraction) in polyamides Or H bonding is stronger (must be a comparison of correct forces to score M3) Do not award if refer to stronger bonds Page 57 of 76

58 (b) (nucleophilic) addition elimination Minus sign on NH 2 loses M M2 not allowed independent of M, but allow M for correct attack on C+ + rather than + on C=O loses M2 If Cl lost with C=O breaking, max for M M3 for correct structure with charges but lp on O is part of M4 only allow M4 after correct/ very close M3 For M4, ignore NH 3 removing H + but lose M4 for Cl removing H + in mechanism, but ignore HCl as a product N-methylpropanamide Not N-methylpropaneamide 4 (c) Allow CONH or COHN Page 58 of 76

59 don t penalize position of + on NH 3 don t penalize position of + on N(CH 3 ) 3 (d) 2-amino-3-hydroxypropanoic acid Must be salts of aspartic acid allow CO 2 allow NH 2 (iii) Penalise use of aspartic acid once in d(iii) and d(iv) allow CO 2 H allow + NH 3 (iv) Penalise use of aspartic acid once in d(iii) and d(iv) allow CO 2 (Br ) must show C-N bond [6] 3 (a) 3-hydroxypropanoic acid allow 3-hydroxypropionic acid must be correct spelling Page 59 of 76

60 (b) must show trailing bonds or can start at any point in the sequence, e.g. not allow dimer allow O CH 2 CH 2 COOCH 2 CH 2 CO or CH 2 CH 2 COOCH 2 CH 2 COO ignore ( ) or n NB answer has a total of 6 carbons and 4 oxygens condensation (polymerisation) Allow close spelling (c) C=C or carbon-carbon double bond must show ALL bonds including O H (iii) must show trailing bonds allow polyalkene conseq on their c ignore n Page 60 of 76

61 (d) allow NH 3+ allow COO (e) In (e), do not penalise a slip in the number of carbons in the -CH 2 CH 2 - chain, but all must be bonded correctly NB two carboxylate groups Allow COONa or COO Na + but not covalent bond to Na allow NH 2 In (e), do not penalise a slip in the number of carbons in the -CH 2 CH 2 - chain, but all must be bonded correctly NB two ester groups allow NH 2 or + NH 3 Page 6 of 76

62 (iii) In 4(e), do not penalise a slip in the number of carbons in the -CH 2 CH 2 - chain, but all must be bonded correctly allow anhydride formation on either or both COOH groups (see below) with or without amide group formation (f) M phase or eluent or solvent (or named solvent) is moving or mobile M2 stationary phase or solid or alumina/silica/resin M3 separation depends on balance between solubility or affinity (of compounds) in each phase OR different adsorption or retention OR (amino acids have) different R f values OR (amino acids) travel at different speeds or take different times [3] 4 (a) hydrolysis not hydration 2-aminopropanoic acid ignore alanine QoL Page 62 of 76

63 (iii) allow CO 2 allow + NH 3 don t penalize position of + on NH 3 (iv) allow CO 2 allow + NH 3 don t penalize position of + on NH 3 (b) allow CO 2 H allow limit as + on N or outside [ ] allow CO 2 H allow CONH or COHN allow NH 2 allow limit as [6] Page 63 of 76

64 5 (a) allow CO 2 allow + NH 3 don t penalize position of + on NH 3 allow CO 2 allow NH 2 allow C 3 H 7 (iii) allow CO 2 H allow + NH 3 don t penalize position of + on NH 3 Page 64 of 76

65 (b) allow CO 2 H allow NH 2 allow C 3 H 7 allow as zwitterions if error in peptide link e.g. (c) if twice, penalise both times not polymers if wrong amino acid in both can score Max chromatography or electrophoresis ignore qualification to chromatography [6] 6 (a) Pt(NH 3 ) 2 Cl 2 + H 2 O [Pt(NH 3 ) 2 Cl(H 2 O)] + + Cl Correct product Balanced equation (b) Hydrogen bond Oxygen (or nitrogen) Only score this mark if type of bond is correct Co-ordinate Nitrogen (or oxygen) Bond type must be correct to score this mark but allow M2 if bond is covalent Page 65 of 76

66 (c) Killing them or causing damage (medical side effects) Allow any correct side effect (e.g. hair loss) Allow kills healthy (or normal) cells May attach to DNA in normal cells [8] 7 (a) (iii) hydrogen bonding (do not allow H-bonding) QWC do not penalise any error twice. (b) (iii) Isomer must be saturated or must not contain a double bond Page 66 of 76

67 (c) 2 (d) heat/reflux with aqu NaOH poly(alkene) is inert/ no reaction polyamide is hydrolysed (or undergoes hydrolysis) to form acid salt and alcohol QWC e.g combustion heat energy produced toxic gases produced [4] 8 (a) CH 3 CH=CHCH 3 Addition or radical (QoL) CH 3 CH(OH)CH(OH)CH 3 or with no brackets butan(e) 2,3 diol or 2,3 butan(e)diol 2,3 dimethylbutan(e)dioic acid ignore,4 condensation (QoL) 2,3 dimethylbutan(e)dioyl chloride Page 67 of 76

68 (iii) NaOH or HCl etc or Na 2 CO 3 Allow conc sulphuric/nitric NOT water nor acidified water nor weak acids (b) Structure Allow CONH and COHN Allow zwitterions NOT polypeptides/repeating units Structure 2 either of (c) CH 3 CH 2 CH 2 Br allow Cl, I (iii) CH 3 CH 2 CN (nucleophilic) substitution or from CH 3 CH 2 CH 2 Br if reduction written here, no further marks further substitution/reaction occurs or other products are formed Allow reduction forms only one product one of (CH 3 CH 2 CH 2 ) 2 NH (CH 3 CH 2 CH 2 ) 3 N (CH 3 CH 2 CH 2 ) 4 N + Br Allow salts including NH 4 Br Allow HBr [5] Page 68 of 76

69 9 (a) polyamide or nylon (2,4) condensation (allow nylon without numbers but if numbers are present they must be correct) (b) (c) ionic bonding in aminoethanoic acid (can only score if includes that aminoethanoic is ionic) stronger attractions than Hydrogen bonding in hydroxyethanoic acid (e.g. stronger Hydrogen bonding in aminoethanoic acid scores 0) (mention of electrostatic forces between molecules scores 0) [5] 20 (a) necleophilic addition; M3 structure; (be lenient on position of charge on CN ) (M2 not allowed independent of M, but allow M for correct attack on C+ if M2 show as independent first.) (+on C of C=O loses M2 but ignore δ+ if correct) (M4 for arrow and lone pair (only allow for correct M3 or close)) 4 Page 69 of 76

70 (b) 2-hydroxybutanoic acid geometric(al) or cis-trans (c) (one unit only) (ignore brackets or n) (trailing bonds are needed) can be hydrolysed OR can be reacted with/attacked by acid/base/nucleophiles/h 2 O/OH ; (d) (allow NH 3+ ) (or zwitterions product) (iii) nucleophilic substitution; [4] Page 70 of 76

71 (c) C 3 H 4 O 2 2 (a) (Ignore n or brackets, but trailing bonds are essential) Addition or radical (b) 2-aminobutanoic (acid) (,4-)butan(e)dioic (acid) (allow succinic, but not dibutanoic nor butanedicarboxylic acid) (iii) Can be hydrolysed / can react with acid or base or water / can react with nucleophiles [8] Page 7 of 76

72 22 (a) () ignore Na + unless covalently bonded () must be dipeptide, not polymer nor anhydride allow CONH or COHN allow zwitterion (iii) hydrogen bonding () QL Allow with dipole-dipole or v derwaals, but not dipole-dipole etc alone 3 (b) Type of polymerisation: addition(al) () Repeating unit: () not multiples allow n Page 72 of 76

73 CH 3 CH=CHCH 2 CH 3 () C 2 H 5 (iii) 4 [7] 23 (a) 2-amino(e) propanoic acid () (b) molecules with same structure / structural formula () but with bonds (atoms or groups) arranged differently in space (3D) () Plane polarised light () Rotated (equally) in opposite directions () (c) () 4 allow H 2 NCH 2 COO Penalise NH 2 and OH once per paper but CH 3 is allowed Page 73 of 76

74 (d) Not anhydrides; not repeating units 2 (e) () or H 2 NCH 2 COOCH 3 [9] 24 (a) 2-chloropropanoic acid () (b) δ.72 Doublet next to CH () δ 4.44 Quartet next to CH 3 () (c) Two triplets () (d) 2 (e) Allow S N 5 Page 74 of 76

75 (iii) Or anhydride 3 [2] 25 (a) hexane-,6-diamine or,6-diaminohexane (allow ammine) or,6 hexan(e)diamine () (b) Allow CONH 2 2 Page 75 of 76

76 (c) quaternary ammonium bromide salt () (not ion, not compound) Allow quarternery Reagent: CH 3 Br or bromomethane () penalise CH 3 Cl but allow excess for any halomethane Condition: excess (CH 3 Br) () (iii) nucleophilic substitution () 4 [8] Page 76 of 76