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The following figure shows a simplified representation of the arrangement of some amino acids ina portion of a protein structure in the form of an α-helix.1
(a) Name the type of protein structure in the figure.
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(b) Explain the origin of the interaction represented by the dotted lines in the figure above.
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(Total 5 marks)
Page 1 of 76
The tripeptide shown in the following figure is formed from the amino acids glycine, threonine andlysine.2
(a) Draw a separate circle around each of the asymmetric carbon atoms in the tripeptide in thefigure.
(1)
(b) Draw the zwitterion of glycine.
(1)
(c) Draw the structure of the species formed when glycine reacts with an excess ofbromomethane.
(1)
(d) Deduce the IUPAC name of threonine.
........................................................................................................................(1)
Page 2 of 76
(e) Draw the structure of the species formed by lysine at low pH.
(1)
(Total 5 marks)
The anticancer drug cisplatin operates by reacting with the guanine in DNA.
Figure 1 shows a small part of a single strand of DNA. Some lone pairs are shown.
Figure 1
3
(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.
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Page 3 of 76
(b) Messenger RNA is synthesised in cells in order to transfer information from DNA. Thebases 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 1 whenmessenger RNA is synthesised.Explain how the base that you have chosen forms a base pair with guanine.
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(c) Cisplatin works because one of the atoms on guanine can form a co-ordinate bond withplatinum, replacing one of the ammonia or chloride ligands. Another atom on anotherguanine can also form a co-ordinate bond with the same platinum by replacing anotherligand.
On Figure 1, draw a ring round an atom in guanine that is likely to bond to platinum.(1)
Page 4 of 76
(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 isminimised.
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(Total 7 marks)
A peptide is hydrolysed to form a solution containing a mixture of amino acids. This mixture isthen analysed by silica gel thin-layer chromatography (TLC) using a toxic solvent. The individualamino acids are identified from their Rf values.
Part of the practical procedure is given below.
1. Wearing plastic gloves to hold a TLC plate, draw a pencil line 1.5 cm from the bottom ofthe plate.
2. Use a capillary tube to apply a very small drop of the solution of amino acids to themid-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 1 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.
4
(a) Parts of the procedure are in bold text.
For each of these parts, consider whether it is essential and justify your answer.
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Page 5 of 76
(b) Outline the steps needed to locate the positions of the amino acids on the TLC plate and todetermine their Rf values.
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(c) Explain why different amino acids have different Rf values.
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(Total 10 marks)
A drug is designed to simulate one of the following molecules that adsorbs onto the active site ofan enzyme.
Which molecule requires the design of an optically active drug?
A
B
C
D (Total 1 mark)
5
Page 6 of 76
(a) The structures and common names of two amino acids are shown.
(i) Draw the structure of the zwitterion of proline.
(1)
(ii) Draw the structure of the tripeptide formed when a proline molecule bonds to twoalanine molecules, one on each side.
(2)
6
(b) Sections of two polymers, L and M, are shown.
(i) Give the IUPAC name of a monomer that forms polymer L.
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(ii) Give the IUPAC name of the monomer that forms polymer M.
...............................................................................................................(1)
Page 7 of 76
(iii) Draw the section of a polymer made from a dicarboxylic acid and a diamine that isisomeric with the section of polymer M shown.
(1)
(vi) Explain why polymer L is non-biodegradable.
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(Total 7 marks)
Lysine and alanine are two amino acids.
lysine
alanine
(a) Give the IUPAC name of lysine.
........................................................................................................................(1)
7
(b) Draw structures to show the product formed in each case when lysine reacts with
(i) an excess of aqueous HCl
(1)
(ii) an excess of aqueous NaOH
(1)
Page 8 of 76
(iii) methanol in the presence of a small amount of concentrated H2SO4
(1)
(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 thatproduces 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.
(1)
(e) The dipeptide in part (d) is hydrolysed in acid conditions and the mixture produced isanalysed by column chromatography. The column is packed with a resin which acts as apolar stationary phase.
Suggest why lysine leaves the column after alanine.
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(Total 9 marks)
Page 9 of 76
Alanine and aspartic acid are naturally occurring amino acids.
(a) Draw the structure of the zwitterion formed by alanine.
(1)
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(b) Draw the structure of the compound formed when alanine reacts with methanol in thepresence of a small amount of concentrated sulfuric acid.
(1)
(c) Draw the structure of the species formed by aspartic acid at high pH.
(1)
(d) Draw the structure of a dipeptide formed by two aspartic acid molecules.
(1)
(Total 4 marks)
Page 10 of 76
(a) The tripeptide shown is formed from the amino acids alanine, threonine and lysine.
(i) Draw a separate circle around each of the asymmetric carbon atoms in the tripeptide.(1)
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(ii) Draw the zwitterion of alanine.
(1)
(iii) Give the IUPAC name of threonine.
...............................................................................................................(1)
(iv) Draw the species formed by lysine at low pH.
(1)
(b) The repeating unit shown represents a polyester.
(i) Name this type of polymer.
...............................................................................................................(1)
(ii) Give the IUPAC name for the alcohol used to prepare this polyester.
...............................................................................................................(1)
Page 11 of 76
(c) The repeating unit shown represents a polyalkene co-polymer. This co-polymer is madefrom two different alkene monomers.
(i) Name the type of polymerisation occurring in the formation of this co-polymer.
...............................................................................................................(1)
(ii) Draw the structure of each alkene monomer.
Alkene monomer 1 Alkene monomer 2
(2)
(d) One of the three compounds shown in parts (a), (b) and (c) cannot be broken down byhydrolysis.
Write the letter (a), (b) or (c) to identify this compound and explain why hydrolysis of thiscompound does not occur.
Compound ....................................................................................................
Explanation ....................................................................................................
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(Total 11 marks)
Page 12 of 76
A possible synthesis of the amino acid X is shown below.
(a) Name and outline a mechanism for Step 1.
Name of mechanism .....................................................................................
Mechanism
(5)
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(b) Give the IUPAC name of the product of Step 2.
........................................................................................................................(1)
(c) For Step 3, give the reagent, give a necessary condition and name the mechanism.
Reagent .........................................................................................................
Condition ........................................................................................................
Name of mechanism .....................................................................................(3)
Page 13 of 76
(d) At room temperature, the amino acid X exists as a solid.
(i) Draw the structure of the species present in the solid amino acid.
(1)
(ii) With reference to your answer to part (d)(i), explain why the melting point of theamino acid X is higher than the melting point of CH3CH2CH(OH)COOH.
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(Extra space) ........................................................................................
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(e) There are many structural isomers of X, CH3CH2CH(NH2)COOH.
(i) Draw a structural isomer of X that is an ethyl ester.
(1)
(ii) Draw a structural isomer of X that is an amide and also a tertiary alcohol.
(1)
Page 14 of 76
(iii) Draw a structural isomer of X that has an unbranched carbon chain and can bepolymerised to form a polyamide.
(1)
(f) Draw the structure of the tertiary amine formed when X reacts with bromomethane.
(1)
(Total 16 marks)
Page 15 of 76
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 withdiabetes.
Hydrolysis of aspartame forms methanol initially. After a longer time the peptide link breaks toform 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 foodsthat are to be cooked.
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(Extra space) .................................................................................................
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(b) Give the IUPAC name of aspartic acid.
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(c) Draw the organic species formed by aspartic acid at high pH.
(1)
Page 16 of 76
(d) Draw the zwitterion of phenylalanine.
(1)
(e) Phenylalanine exists as a pair of stereoisomers.
(i) State the meaning of the term stereoisomers.
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(ii) Explain how a pair of stereoisomers can be distinguished.
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(Total 8 marks)
Page 17 of 76
The amide or peptide link is found in synthetic polyamides and also in naturallyoccurring proteins.
(a) (i) Draw the repeating unit of the polyamide formed by the reaction of propanedioic acidwith hexane-1,6-diamine.
(2)
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(ii) In terms of the intermolecular forces between the polymer chains, explain whypolyamides can be made into fibres suitable for use in sewing and weaving, whereaspolyalkenes usually produce fibres that are too weak for this purpose.
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Page 18 of 76
(b) (i) Name and outline a mechanism for the reaction of CH3CH2COCl with CH3NH2
Name of mechanism............................................................................
Mechanism
(5)
(ii) Give the name of the product containing an amide linkage that is formed in thereaction in part (b) (i).
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(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 aminoacids.
(1)
Page 19 of 76
(d) The amino acids serine and aspartic acid are shown below.
(i) Give the IUPAC name of serine.
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(ii) Draw the structure of the species formed when aspartic acid reacts with aqueoussodium hydroxide.
(1)
(iii) Draw the structure of the species formed when serine reacts with dilute hydrochloricacid.
(1)
(iv) Draw the structure of the species formed when serine reacts with an excess ofbromomethane.
(1)
(Total 16 marks)
Page 20 of 76
(a) Name compound Y, HOCH2CH2COOH
......................................................................................................................(1)
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(b) Under suitable conditions, molecules of Y can react with each other to form a polymer.
(i) Draw a section of the polymer showing two repeating units.
(1)
(ii) Name the type of polymerisation involved.
.............................................................................................................(1)
(c) When Y is heated, an elimination reaction occurs in which one molecule of Y loses onemolecule of water. The organic product formed by this reaction has an absorption at
1637 cm–1 in its infrared spectrum.
(i) Identify the bond that causes the absorption at 1637 cm–1 in its infrared spectrum.
.............................................................................................................(1)
(ii) Write the displayed formula for the organic product of this elimination reaction.
(1)
(iii) The organic product from part (ii) can also be polymerised.Draw the repeating unit of the polymer formed from this organic product.
(1)
Page 21 of 76
(d) At room temperature, 2-aminobutanoic acid exists as a solid.Draw the structure of the species present in the solid form.
(1)
(e) The amino acid, glutamic acid, is shown below.
Draw the structure of the organic species formed when glutamic acid reacts with each ofthe following.
(i) an excess of sodium hydroxide
(1)
(ii) an excess of methanol in the presence of concentrated sulfuric acid
(1)
(iii) ethanoyl chloride
(1)
Page 22 of 76
(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.
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(Total 13 marks)
(a) Consider the tripeptide shown below that is formed from three amino acids, K, L and M.
(i) Name the process by which the tripeptide is split into three amino acids.
.............................................................................................................(1)
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(ii) Give the IUPAC name for the amino acid K.
.............................................................................................................(1)
(iii) Draw the structure of the zwitterion of amino acid L.
(1)
Page 23 of 76
(iv) Draw the structure of the species formed by amino acid M at low pH.
(1)
(b) Consider the amino acid serine.
(i) Draw the structure of the product formed when serine reacts with an excess of CH3Br
(1)
(ii) Draw the structure of the dipeptide formed by two molecules of serine.
(1)
(Total 6 marks)
Page 24 of 76
The three amino acids shown below were obtained by hydrolysis of a protein.
(a) (i) Draw the zwitterion of alanine.
(1)
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(ii) Draw the species formed when valine is dissolved in an alkaline solution.
(1)
(iii) Draw the species formed by lysine at low pH.
(1)
(b) Draw the two dipeptides formed by the reaction of alanine with valine.
(2)
Page 25 of 76
(c) Name a suitable method by which the mixture of amino acids formed by hydrolysis of theprotein can be separated.
......................................................................................................................(1)
(Total 6 marks)
The complex cisplatin acts as an anticancer drug by changing the properties of DNA when itreacts with guanine, a component of DNA.
When cisplatin is absorbed into the human body, it undergoes a ligand substitution reaction andone 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.
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(b) The complex ion Q can bond to guanine in two different ways.
(i) 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 guanineand 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
(ii) The second way involves a ligand substitution reaction in which an atom in a guaninemolecule bonds to platinum by displacing the water molecule from Q.State the type of bond formed between guanine and platinum when a water moleculeis 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)
Fibres are made from natural and from synthetic polymers. Both types of polymer haveadvantages and disadvantages.
(a) Amino acids are the building blocks of naturally-occurring polymers called proteins.
Consider the following amino acid.
(i) Draw the structure of the amino acid species present in a solution at pH 12.
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(ii) Use your understanding of amino acid chemistry to deduce the structure of thedipeptide formed from two molecules of this amino acid and illustrate your answerwith a sketch showing the structure of the dipeptide.
Page 27 of 76
(iii) Protein chains are often arranged in the shape of a helix. Name the type ofinteraction that is responsible for holding the protein chain in this shape.
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(b) Alkenes are the building blocks of synthetic addition polymers.
Consider the hydrocarbon G, (CH3)2C=CHCH3, which can be polymerised.
(i) Draw the repeating unit of the polymer.
(ii) 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 acidand hexane-1,6-diamine.
(2)
Page 28 of 76
(d) Two plastic objects were manufactured, one from the polyalkene represented by therepeating unit in part (b)(i) and the other from the polyamide represented by the repeatingunit in part (c).
After use it was suggested that both objects be disposed of as landfill.
(i) Describe an experiment in which you could compare the biodegradability of these twoobjects.
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(ii) Describe an advantage or a disadvantage of a different method of disposal of suchobjects compared with landfill.
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(Total 14 marks)
Page 29 of 76
(a) The repeating units of two polymers, P and Q, are shown below.
(i) Draw the structure of the monomer used to form polymer P. Name the type ofpolymerisation involved.
Structure of monomer
Type of polymerisation .......................................................................
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(ii) 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 1
Name of compound 1 .........................................................................
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 notpolymer P.
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Page 30 of 76
(b) Draw the structures of the two dipeptides which can form when one of the amino acidsshown below reacts with the other.
Structure 1 Structure 2(2)
(c) Propylamine, CH3CH2CH2NH2, can be formed either by nucleophilic substitution or byreduction.
(i) Draw the structure of a compound which can undergo nucleophilic substitution toform propylamine.
(ii) 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 substitutionor by reduction, gives the less pure product. Draw the structure of a compoundformed as an impurity.
Route giving the less pure product .....................................................
Explanation .........................................................................................
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Structure of an impurity
(5)
(Total 15 marks)
Page 31 of 76
(a) The structure below shows the repeating unit of a polymer.
By considering the functional group formed during polymerisation, name this type ofpolymer and the type of polymerisation involved in its formation.
Type of polymer ...........................................................................................
Type of polymerisation .................................................................................(2)
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(b) Draw the structure of the species present in solid aminoethanoic acid, H2NCH2COOH
(1)
(c) Explain why the melting point of aminoethanoic acid is much higher than that ofhydroxyethanoic acid, HOCH2COOH
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(Total 5 marks)
Page 32 of 76
Consider the reaction sequence shown below.
(a) Name and outline a mechanism for the reaction in Step 1.
Name of mechanism ....................................................................................
Mechanism
(5)
20
Page 33 of 76
(b) (i) Name compound Q formed in Step 2.
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(ii) Two stereoisomers are formed by the dehydration of Q. Give the structures of thesetwo 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 thebiodegradeable polymer known as PHB.
(i) Draw the repeating unit of the polymer PHB.
(ii) Suggest a reason why the polymer is biodegradeable.
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Page 34 of 76
(d) The amino acid R is shown below.
(i) Draw the structure of the zwitterion formed by R.
(ii) Draw the structure of the major organic product formed when an excess of R isreacted with bromomethane.
(iii) Name the mechanism of the reaction which results in the formation of the productgiven in part (ii).
.............................................................................................................(3)
(Total 14 marks)
Page 35 of 76
(a) The compound H2C=CHCN is used in the formation of acrylic polymers.
(i) Draw the repeating unit of the polymer formed from this compound.
(ii) Name the type of polymerisation involved in the formation of this polymer.
.............................................................................................................(2)
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(b) When the dipeptide shown below is heated under acidic conditions, a single amino acid isproduced.
(i) Name this amino acid.
.............................................................................................................
(ii) Draw the structure of the amino acid species present in the acidic solution.
(2)
(c) The repeating unit of a polyester is shown below.
(i) Deduce the empirical formula of the repeating unit of this polyester.
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Page 36 of 76
(ii) Draw the structure of the acid which could be used in the preparation of this polyesterand give the name of this acid.
Structure ..............................................................................................
Name ...................................................................................................
(iii) Give one reason why the polyester is biodegradable.
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(Total 8 marks)
(a) Consider the following amino acid.
(i) Draw the structure of the amino acid species present in a solution at pH 12.
22
(ii) Draw the structure of the dipeptide formed from two molecules of this amino acid.
Page 37 of 76
(iii) Protein chains are often arranged in the shape of a helix. Name the type ofinteraction that is responsible for holding the protein chain in this shape.
.............................................................................................................(3)
(b) Consider the hydrocarbon G, (CH3)2C=CHCH3, which can be polymerised.
(i) Name the type of polymerisation involved and draw the repeating unit of the polymer.
Type of polymerisation ........................................................................
Repeating unit
(ii) 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
The structures of the amino acids alanine and glycine are shown below.
(a) Give the systematic name for alanine.
......................................................................................................................(1)
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(b) Alanine exists as a pair of stereoisomers.
(i) Explain the meaning of the term stereoisomers.
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(ii) State how you could distinguish between the stereoisomers.
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(c) Give the structural formula of the species formed by glycine at pH 14.
(1)
Page 39 of 76
(d) When two amino acids react together, a dipeptide is formed. Give the structural formulae ofthe two dipeptides which are formed when alanine and glycine react together.
Dipeptide 1
Dipeptide 2
(2)
(e) Give the structural formula of the organic compound formed when glycine reacts withmethanol in the presence of a small amount of concentrated sulphuric acid.
(1)
(Total 9 marks)
Page 40 of 76
Three sections of the proton n.m.r. spectrum of CH3CHClCOOH are shown below.
(a) Name the compound CH3CHClCOOH
......................................................................................................................(1)
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(b) Explain the splitting patterns in the peaks at δ 1.72 and δ 4.44
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(c) Predict the splitting pattern that would be seen in the proton n.m.r. spectrum of the isomericcompound ClCH2CH2COOH
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Page 41 of 76
(d) The amino acid alanine is formed by the reaction of CH3CHClCOOH with an excess ofammonia. The mechanism is nucleophilic substitution. Outline this mechanism, showingclearly 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
(i) an excess of aqueous HCl,
(ii) an excess of aqueous NaOH,
Page 42 of 76
(iii) another molecule of lysine.
(3)
(Total 12 marks)
(a) Synthetic polyamides are produced by the reaction of dicarboxylic acids with compoundssuch as H2N(CH2)6NH2
(i) Name the compound H2N(CH2)6NH2
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(ii) Give the repeating unit in the polyamide nylon 6,6.
.............................................................................................................(2)
(b) Synthetic polyamides have structures similar to those found in proteins.
(i) Draw the structure of 2-aminopropanoic acid.
(ii) Draw the organic product formed by the condensation of two molecules of2-aminopropanoic acid.
(2)
Page 43 of 76
(c) Compounds like H2N(CH2)6NH2 are also used to make ionic compounds such as X, shownbelow.
(i) X belongs to the same type of compound as (CH3)4N+Br–
Name this type of compound.
.............................................................................................................
(ii) State a reagent which could produce X from H2N(CH2)6NH2 and give a necessarycondition 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
Mark schemes
(a) Secondary11
(b) Nitrogen and oxygen are very electronegative1
Therefore, C=O and N–H are polar1
Which results in the formation of a hydrogen bond between O and H1
In which a lone pair of electrons on an oxygen atom is strongly attracted to the δ+H1
[5]
(a)
1
2
(b)
1
(c)
Allow
1
(d) 2-amino-3-hydroxybutanoic acid1
Page 45 of 76
(e)
1[5]
(a) 2-deoxyribose13
(b) Base A
If Base B stated, allow 1 mark only for response including hydrogenbonding
1
Top N–H forms hydrogen bonds to lone pair on O of guanine1
The lone pair of electrons on N bonds to H–N of guanine1
A lone pair of electrons on O bonds to lower H–N of guanine
Allow all 4 marks for a correct diagram showing the hydrogenbonding
Students could also answer this question using labels on thediagram
1
(c) Allow either of the nitrogen atoms with a lone pair NOT involved in bonding tocytosine
1
(d) Use in very small amounts / target the application to the tumour1
[7]
(a) Wear plastic gloves:
Essential – to prevent contamination from the hands to the plate1
4
Add developing solvent to a depth of not more than 1 cm3:
Essential – if the solvent is too deep it will dissolve the mixture from the plate1
Allow the solvent to rise up the plate to the top:
Not essential – the Rf value can be calculated if the solvent front does not reach thetop of the plate
1
Page 46 of 76
Allow the plate to dry in a fume cupboard:
Essential – the solvent is toxic
Allow hazardous1
(b) Spray with developing agent or use UV1
Measure distances from initial pencil line to the spots (x)1
Measure distance from initial pencil line to solvent front line (y)1
Rf value = x / y1
(c) Amino acids have different polarities1
Therefore, have different retention on the stationary phase or different solubility in thedeveloping solvent
1[10]
C[1]5
Page 47 of 76
(a) (i)
Allow CO2- and NH2
+
1
(ii) NOTE − Two marks for this clip
M1 for alanine section bonded through N
M2 for alanine section bonded through C
But penalise error in proline ring1
Allow MAX 1 for correct tripeptide in polymer structure1
6
(b) (i) 3-methylpent-2-ene
Ignore E-Z, commas, spaces or missing hyphens1
(ii) 4-amino-3-methylbutanoic acid
Ignore commas, spaces or missing hyphens1
(iii)
or any polyamide section containing
8 carbons plus two C=O plus two N-H, such as
Trailing bonds are required1
Page 48 of 76
(iv) Non polar OR no polar groups / bonds (for attack by water / acids / alkalis /nucleophiles or for hydrolysis)
C-C bonds are strong1
[7]
(a) 2,6-diaminohexanoic acid
Ignore additional , or – or spaces.1
7
(b) (i)
NB both N must be protonated.
Allow −NH3+ allow CO2H Allow −+H3N.
Penalise – C4H8 – here.1
(ii)
Allow CO2−.
Allow −H2N.
Allow –COONa but penalise O–Na bond shown.1
(iii)
Allow CO2CH3.
Allow −NH3+ or –H2N.
1
Page 49 of 76
(c)
1 for displayed formula of fragment ion.
1 for molecular ion of alanine AND radical.
Allow molecular ion without brackets and fragment ion in bracketswith outside +.
Allow dot anywhere on radical.
Allow [C3H7NO2] for molecular ion.2
(d)
OR
OR
Dipeptide, not repeating unit /.
Allow CO2H Allow –H2N.
Allow –CONH–.1
(e) M1 In acid lysine has double positive or more positive charge1
M2 (Lysine ion) has greater affinity / greater attraction / adheres better / sticks better to polar / stationary phase
M2 only scores after a correct M1.
Ignore greater retention time.1
[9]
Page 50 of 76
(a)
Allow −NH3+ and +NH3−
1
8
(b)
Allow protonated form, i.e. −NH3+ or +NH3−
1
(c)
Allow – CO2–
1
(d)
Allow zwitterion with any COO−
Allow use of “wrong” COOH
1[4]
Page 51 of 76
(a) (i)
These four only1
9
(ii)
Allow − NH3+ and +NH3−
1
(iii) 2-amino-3-hydroxybutanoic acid
Ignore 1 in butan-1-oic acid
Do not penalise commas or missing hyphens
Penalise other numbers1
(iv)
Allow –NH3+ and +NH3−
1
(b) (i) Condensation
Allow polyester1
(ii) propane-1,3-diol
Must have e
Allow 1,3-propanediol1
Page 52 of 76
(c) (i) Addition
Not additional1
(ii)
Allow monomers drawn either way round
Allow bond to F in CF3
1
OR
1 for each structure within each pair1
(d) c
If wrong, CE = 01
C-C or C-F bonds too strong1
[11]
Page 53 of 76
(a)
• allow :CN–
• M2 not allowed independent of M1, but
• allow M1 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
• Allow C 2H5
• M1 and M4 for lp and curly arrow1
10
(b) 2-bromobutanenitrile
Allow 2-bromobutane-1-nitrile1
(c) M1 ammonia or NH3
Ignore temp or pressure1
M2 excess (ammonia) excess tied to NH3 and may score in M1 unlesscontradicted
Ignore concentrated or sealed container, Acid loses conditions mark1
M3 nucleophilic substitution
Allow close spelling1
(d) (i)
Allow C2H5
Allow –CO2–
Allow +NH3–
Don’t penalize position of + on NH 3
1
Page 54 of 76
(ii) M1 electrostatic forces between ions in X QOL
Allow ionic bonding.1
Marks independent
M2 (stronger than) hydrogen bonding between CH3CH2CH(OH)COOH
CE mention of molecules of X or inter molecular forces between Xloses both marks
1
(e) (i)
OR
Isomer of C4H9NO2
Allow NH2–1
(ii)
Isomer of C4H9NO2 allow NH2–
1
Allow
(iii) H2N–CH2CH2CH2–COOH or H2N–(CH2)3–COOH
Isomer of C4H9NO2 allow NH2–
OR
Do not allow –C3H6-
Beware – do not credit X itself1
Page 55 of 76
(f)
Answer has 6 carbons so NOT isomer of X
Allow C2H5
Must have bond from C to N not to methyl group1
[16]
(a) Heating speeds up (hydrolysis / breaking of peptide bonds)
OR forms non-sweet (amino acids)1
11
(b) (2-)aminobutanedioic acid OR
2 not necessary but penalise other numbers at start
(2-)aminobutane(-1,4-)dioic acid
1,4 not necessary but penalise other numbers and 1,4 must be incorrect place (QoL)
1
(c)
allow –CO2–
allow NH2–1
(d)
allow –CO2–
allow +NH3–
don’t penalize position of + on NH 3
1
Page 56 of 76
(e) (i) M1 Compounds/molecules with same structural formula
Not just structure1
M2 But with bonds/atoms/groups arranged differently in space or in 3D
Allow –with different spatial arrangement of atom/bond/group1
Independent marks
(ii) (Plane) polarised light1
Rotated in opposite directions
Not bent or turned or twisted; not different directions (QoL)1
[8]
(a) (i)
Allow –CONH- or - COHN -
Mark two halves separately
lose 1 each for missing trailing bonds at one or both ends or error inpeptide link or either or both of H or OH on ends
1
Not allow –(C6H12)–
Ignore n1
12
(ii) M1 in polyamides - H bonding1
M2 in polyalkenes - van der Waals forces
Penalise forces between atoms or van der Waals bonds1
M3 Stronger forces (of attraction) in polyamidesOr H bonding is stronger(must be a comparison of correct forces to score M3)
Do not award if refer to stronger bonds1
Page 57 of 76
(b) (i) (nucleophilic) addition elimination
Minus sign on NH2 loses M11
M2 not allowed independent of M1, but allow M1 for correct attackon C+
+ rather than + on C=O loses M2
If Cl lost with C=O breaking, max 1 for M1
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 NH3 removing H+ but lose
M4 for Cl removing H+ in mechanism,
but ignore HCl as a product4
(ii) N-methylpropanamide
Not N-methylpropaneamide1
(c)
Allow –CONH– or –COHN–1
Page 58 of 76
(d) (i) 2-amino-3-hydroxypropanoic acid1
(ii)
Must be salts of aspartic acid
allow –CO2–
allow NH2–1
(iii) Penalise use of aspartic acid once in d(iii) and d(iv)
allow –CO2H
allow +NH3–
don’t penalize position of + on NH3
1
(iv) Penalise use of aspartic acid once in d(iii) and d(iv)
(Br–)
allow –CO2–
must show C-N bond
don’t penalize position of + on N(CH3)3
1[16]
(a) 3-hydroxypropanoic acid
allow 3-hydroxypropionic acidmust be correct spelling
1
13
Page 59 of 76
(b) (i) must show trailing bonds
or can start at any point in the sequence, e.g.
not allow dimer
allow –O–CH2CH2COOCH2CH2CO–
or –CH2CH2COOCH2CH2COO–
ignore ( ) or n
NB answer has a total of 6 carbons and 4 oxygens1
(ii) condensation (polymerisation)
Allow close spelling1
(c) (i) C=C or carbon-carbon double bond1
(ii)
must show ALL bonds including O–H1
(iii) must show trailing bonds
allow polyalkene conseq on their c(ii)
ignore n1
Page 60 of 76
(d)
allow NH3+ —
allow COO–
1
(e) (i)
In (e), do not penalise a slip in the number of carbons in the-CH2CH2- chain, but all must be bonded correctly
NB two carboxylate groups
Allow COONa or COO– Na+ but not covalent bond to Na
allow NH2–1
(ii)
In (e), do not penalise a slip in the number of carbons in the-CH2CH2- chain, but all must be bonded correctly
NB two ester groups
allow NH2– or +NH3–1
Page 61 of 76
(iii)
In 4(e), do not penalise a slip in the number of carbons in the-CH2CH2- chain, but all must be bonded correctly
allow anhydride formation on either or both COOH groups (seebelow) with or without amide group formation
1
(f) M1 phase or eluent or solvent (or named solvent) is moving or mobile1
M2 stationary phase or solid or alumina/silica/resin1
M3 separation depends on balance between solubility or affinity(of compounds) in each phaseORdifferent adsorption or retentionOR(amino acids have) different Rf valuesOR(amino acids) travel at different speeds or take different times
1[13]
(a) (i) hydrolysis
not hydration1
(ii) 2-aminopropanoic acid
ignore alanineQoL
1
14
Page 62 of 76
(iii)
allow –CO2–
allow +NH3–don’t penalize position of + on NH 3
1
(iv)
allow –CO2–
allow +NH3–don’t penalize position of + on NH 3
1
(b) (i)
allow –CO2H
+ on N or outside [ ]1
allow limit as
(ii)
allow –CO2H allow –CONH– or –COHN–
allow NH2–
1[6]
allow limit as
Page 63 of 76
(a) (i)
allow –CO2–
allow +NH3–don’t penalize position of + on NH 3
1
15
(ii)
allow –CO2–
allow NH2–allow C3H7
1
(iii)
allow –CO2H
allow +NH3–don’t penalize position of + on NH 3
1
Page 64 of 76
(b)
1
allow –CO2Hallow NH2–allow C3H7
allow as zwitterionsif error in peptide link e.g.
if twice, penalise both timesnot polymersif wrong amino acid in both can score Max 1
1
(c) chromatography or electrophoresis
ignore qualification to chromatography1
[6]
(a) Pt(NH3)2Cl2 + H2O → [Pt(NH3)2Cl(H2O)]+ + Cl–
Correct product1
Balanced equation1
16
(b) (i) Hydrogen bond1
Oxygen (or nitrogen)
Only score this mark if type of bond is correct1
(ii) Co-ordinate1
Nitrogen (or oxygen)
Bond type must be correct to score this mark but allow M2 if bond iscovalent
1
Page 65 of 76
(c) Killing them or causing damage (medical side effects)
Allow any correct side effect (e.g. hair loss)Allow kills healthy (or normal) cells
1
May attach to DNA in normal cells1
[8]
(a) (i)
1
17
(ii)
1
(iii) hydrogen bonding (do not allow H-bonding) QWC
do not penalise any error twice.1
(b) (i)
1
(ii)
1
(iii) Isomer must be saturated or must not contain a double bond1
Page 66 of 76
(c)
2
(d) (i) heat/reflux with aqu NaOH1
poly(alkene) is inert/ no reaction1
polyamide is hydrolysed (or undergoes hydrolysis)to form acid salt and alcohol QWC
1
(ii) e.g combustion1
heat energy produced1
toxic gases produced1
[14]
(a) (i) CH3CH=CHCH3
1
Addition or radical (QoL)1
18
(ii) CH3CH(OH)CH(OH)CH3 or with no brackets1
butan(e)–2,3–diol or 2,3–butan(e)diol1
1
2,3–dimethylbutan(e)dioic acid 2,3–dimethylbutan(e)dioyl chloride
ignore –1,4–1
condensation (QoL)1
Page 67 of 76
(iii) NaOH or HCl etc or Na2CO3
Allow conc sulphuric/nitric
NOT water nor acidified water nor weak acids1
(b) Structure 1
Allow –CONH– and –COHN–
Allow zwitterions
NOT polypeptides/repeating units1
Structure 2 either of
1
(c) (i) CH3CH2CH2Br
allow –Cl, –I1
(ii) CH3CH2CN1
(iii) (nucleophilic) substitution or from CH3CH2CH2Br
if reduction written here, no further marks1
further substitution/reaction occurs or other products are formed
Allow reduction forms only one product1
one of(CH3CH2CH2)2NH(CH3CH2CH2)3N
(CH3CH2CH2)4N+ Br–
Allow salts including NH4Br
Allow HBr1
[15]
Page 68 of 76
(a) polyamide or nylon (2,4)
(allow nylon without numbers but if numbers are present they mustbe correct)
1
condensation1
(b) 1
19
(c) ionic bonding in aminoethanoic acid
(can only score if includes that aminoethanoic is ionic)1
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)1
[5]
(a) necleophilic addition;
1
M3 structure;
(be lenient on position of charge on CN– )(M2 not allowed independent of M1,but allow M1 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
20
Page 69 of 76
(b) (i) 2-hydroxybutanoic acid1
(ii)
1
geometric(al) or cis-trans1
(c) (i)
(one unit only) (ignore brackets or n) (trailing bonds are needed)1
(ii) can be hydrolysed
OR
can be reacted with/attacked by acid/base/nucleophiles/H2O/OH–;1
(d) (i)
(allow –NH3+)
1
(ii)
(or zwitterions product)1
(iii) nucleophilic substitution;1
[14]
Page 70 of 76
(a) (i)
(Ignore n or brackets, but trailing bonds are essential)1
(ii) Addition or radical1
21
(b) (i) 2-aminobutanoic (acid)1
(ii)
1
(c) (i) C3H4O2
1
(ii)
1
(1,4-)butan(e)dioic (acid)
(allow succinic, but not dibutanoic nor butanedicarboxylic acid)1
(iii) Can be hydrolysed / can react with acid or base or water /can react with nucleophiles
1[8]
Page 71 of 76
ignore Na+ unless covalently bonded
must be dipeptide, not polymer nor anhydrideallow –CONH– or –COHN–
allow zwitterion
(iii) hydrogen bonding (1)
QL
Allow with dipole-dipole or v derWaals, but not dipole-dipole etcalone
3
22 (a) (i) (1)
(ii) (1)
(b) (i) Type of polymerisation: addition(al) (1)
not multiples
allow n
Repeating unit: (1)
Page 72 of 76
(ii) CH3CH=CHCH2CH3 (1) C2H5
(iii)
4[7]
(a) 2-amino(e) propanoic acid (1)123
(b) (i) molecules with same structure / structural formula (1)but with bonds (atoms or groups) arranged differently inspace (3D) (1)
(ii) Plane polarised light (1)Rotated (equally) in opposite directions (1)
4
allow H2NCH2COO–
Penalise NH2‑ and OH‑ once per paperbut CH3– is allowed
1
(c) (1)
Page 73 of 76
Not anhydrides; not repeating units2
(d)
or H2NCH2COOCH3
1[9]
(e) (1)
(a) 2-chloropropanoic acid (1)124
(b) δ 1.72 Doublet next to CH (1)
δ 4.44 Quartet next to CH3 (1)2
(c) Two triplets (1)1
(d)
Allow SN15
(e) (i)
(ii)
Page 74 of 76
(iii)
Or anhydride3
[12]
(a) (i) hexane-1,6-diamine or 1,6-diaminohexane (allow ammine)or 1,6 hexan(e)diamine (1)25
Allow –CONH–2
(ii)
(b) (i)
2
(ii)
Page 75 of 76
(c) (i) quaternary ammonium bromide salt (1)
(not ion, not compound)
Allow quarternery
(ii) Reagent: CH3Br or bromomethane (1)
penalise CH3Cl but allow excess for any halomethane
Condition: excess (CH3Br) (1)
(iii) nucleophilic substitution (1)4
[8]
Page 76 of 76
