Z-Retinal, shown in the diagram, is a component in vitamin ...

Z-Retinal, shown in the diagram, is a component in vitamin A.

Which of the double bonds, labelled A, B, C or D, is responsible for the letter Z in the name?

A

B

C

D

(Total 1 mark)

1

Alkenes are useful intermediates in the synthesis of organic compounds.

(a) (i) Complete the elimination mechanism by drawing appropriate curly arrows.

(3)

2

Page 1 of 23Catalyst Tutors

(ii) Draw structures for the E and Z stereoisomers of hex-3-ene.

E isomer of hex-3-ene Z isomer of hex-3-ene

(2)

(iii) State the meaning of the term stereoisomers.

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(Extra space) ___________________________________________________

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(2)

(b) The equation for the first reaction in the conversion of hex-3-ene into hexan-3-ol is shownbelow.

CH3CH2CH=CHCH2CH3 + H2SO4 CH3CH2CH2CH(OSO2OH)CH2CH3

Outline a mechanism for this reaction.

(4)

(Total 11 marks)


(a) Give the formula of a Group 2 metal hydroxide used in agriculture.

___________________________________________________________________

(1)

(b) Identify a sodium halide that does not undergo a redox reaction when added as a solid toconcentrated sulfuric acid.

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(1)

3

(c) Chlorine gas reacts with cold dilute sodium hydroxide solution to form sodium chloride andanother chlorine-containing compound, X.

Give the formula of X.

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(1)

(d) Give the formula of the substance responsible for the orange colour when chlorine gas isbubbled through an aqueous solution of sodium bromide.

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(1)

(e) Solid sodium iodide undergoes a redox reaction with concentrated sulfuric acid.

Give the formula for each of the following in this reaction.

Formula of the solid reduction product ___________________________________

Formula of the oxidation product ________________________________________

(2)

(f) Draw the structure of each of the following organic compounds.

(i) The hydrocarbon that is a chain isomer of methylpropene, but does not exhibit E–Zstereoisomerism.

(1)


(ii) The alcohol that is a position isomer of butan-2-ol.

(1)

(iii) The hydrocarbon that has a peak, due to its molecular ion, at m/z = 44 in its massspectrum.

(1)

(iv) The bromoalkane that reacts with sodium cyanide to produce propanenitrile.

(1)

(Total 10 marks)


The table below shows the structures of three isomers with the molecular formula C5H10O

Isomer 1

(E)-pent-3-en-2-ol

Isomer 2

pentanal

Isomer 3

(a) Complete the table by naming Isomer 3.

(1)

4

(b) State the type of structural isomerism shown by these three isomers.

___________________________________________________________________

(1)

(c) The compound (Z)-pent-3-en-2-ol is a stereoisomer of (E)-pent-3-en-2-ol.

(i) Draw the structure of (Z)-pent-3-en-2-ol.

(1)

(ii) Identify the feature of the double bond in (E)-pent-3-en-2-ol and that in(Z)-pent-3-en-2-ol that causes these two compounds to be stereoisomers.

______________________________________________________________

(1)


(d) A chemical test can be used to distinguish between separate samples of Isomer 2 andIsomer 3.Identify a suitable reagent for the test.State what you would observe with Isomer 2 and with Isomer 3.

Test reagent _________________________________________________________

Observation with Isomer 2 ______________________________________________

___________________________________________________________________

Observation with Isomer 3 ______________________________________________

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(3)

(e) The following is the infrared spectrum of one of the isomers 1, 2 or 3.

(i) Deduce which of the isomers (1, 2 or 3) would give this infrared spectrum. You mayfind it helpful to refer to Table 1 on the Data Sheet.

______________________________________________________________

(1)


(ii) Identify two features of the infrared spectrum that support your deduction.In each case, identify the functional group responsible.

Feature 1 and functional group _____________________________________

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Feature 2 and functional group _____________________________________

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(2)

(Total 10 marks)

The alkene (Z)-3-methylpent-2-ene reacts with hydrogen bromide as shown below.

(a) (i) Name the major product P.

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(1)

5

(ii) Name the mechanism for these reactions.

______________________________________________________________

(1)


(iii) Draw the displayed formula for the minor product Q and state the type of structuralisomerism shown by P and Q.

Displayed formula for Q

Type of structural isomerism _______________________________________

(2)

(iv) Draw the structure of the (E)-stereoisomer of 3-methylpent-2-ene.

(1)

(b) The infrared spectra of two compounds R and S are shown below. R and S have themolecular formula C6H12 and are structural isomers of 3-methylpent-2-ene. R is anunsaturated hydrocarbon and S is a saturated hydrocarbon.

Spectrum 1


Spectrum 2

(i) Identify the infrared Spectrum 1 or 2 that represents compound R.Use information from the infrared spectra to give one reason for your answer.You may find it helpful to refer to Table 1 on the Data Sheet.

R is represented by Spectrum ________

Reason _______________________________________________________

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(2)

(ii) State the type of structural isomerism shown by R and S.

______________________________________________________________

(1)

(iii) Name one possible compound which could be S.

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(1)

(Total 9 marks)

The reaction of bromine with an alkene is used in a test to show that the alkene is unsaturated.

(a) State what is meant by the term unsaturated as applied to an alkene.

___________________________________________________________________

(1)

6


(b) Name and outline a mechanism for the reaction of bromine with but-2-ene.

Name of mechanism __________________________________________________

Mechanism

(5)

(c) But-2-ene can exist as a pair of stereoisomers.

(i) State what is meant by the term stereoisomers.

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)

(ii) Draw the structure of (E)-but-2-ene.

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(1)

(Total 9 marks)

(a) Compounds with double bonds between carbon atoms can exhibit geometrical isomerism.

(i) Draw structures for the two geometrical isomers of 1,2-dichloroethene.

Isomer 1 Isomer 2

7


(ii) What feature of the double bond prevents isomer 1 from changing into isomer 2?

______________________________________________________________

(3)

(b) When 2-chloropropane reacts with sodium hydroxide, two different reactions occur.Each reaction produces a different organic product.

(i) Outline a mechanism for Reaction 1 and state the role of the hydroxide ion in thisreaction.

Mechanism

Role of the hydroxide ion __________________________________________

(ii) Outline a mechanism for Reaction 2 and state the role of the hydroxide ion in thisreaction.

Mechanism

Role of the hydroxide ion __________________________________________

(7)

(Total 10 marks)


The correct systematic name for is

A 2-ethyl-3,4-dimethylpent-2-ene

B 4-ethyl-2,3-dimethylpent-3-ene

C 2,3,4-trirnethylhex-3-ene

D 3,4,5-trimethylhex-3-ene

(Total 1 mark)

8


Mark schemes

C

[1]1

(a) (i)

Penalise one mark from their total if half-headed arrows are used

Penalise M3 for formal charge on C of the C-Br or incorrect partialcharges on C-Br

Ignore other partial charges

2

M1 must show an arrow from the lone pair on oxygen of a negatively chargedhydroxide ion to the correct H atom

Penalise once only in any part of the mechanism for a line and twodots to show a bond.

M2 must show an arrow from the correct C–H bond to the correct C–C bond.Only award if an arrow is shown attacking the H atom of the correct C–Hbond in M1

M3 is independent but CE=0 if nucleophilic substitution

N.B these are double-headed arrows3

(ii)

Award 1 mark if both correct stereoisomers but in the wrong places

Accept no other alkenes.

Be reasonably lenient on the bonds to ethyl (or to CH2CH3) sincethe question is about E and Z positions but penalise once only ifconnection is clearly to the CH3 of CH2CH3

Accept linear structures2


(iii) M1 (Compounds / molecules with) the same structural formula

Penalise M1 if “same structure”

M2 with atoms/bonds/groups arranged differently in space

Ignore references to “same molecular formula” or “same empiricalformula” or any reference to “displayed formula”

ORatoms/bonds/groups that have different spatial arrangements / differentorientation.

Mark independently2


(b)

M1must show an arrow from the double bond towards the H atom of the H – O bondOR HO on a compound with molecular formula for H2SO4

M1 could be to an H+ ion and M2 an independent O – H bond break on a compound withmolecular formula for H2SO4

M1 Ignore partial negative charge on the double bond.

M2 must show the breaking of the O – H bond.

M2 Penalise partial charges on O – H bond if wrong way andpenalise formal charges

In M2 do not penalise incorrect structures for H2SO4

M3 is for the structure of the carbocation.

M4 must show an arrow from the lone pair of electrons on the correct oxygen of thenegatively charged ion towards a correct (positively charged) carbon atom.

M4 NOT HSO4–

For M4, credit as shown or –:OSO3H ONLY with the negativecharge anywhere on this ion

OR correctly drawn out with the negative charge placed correctly onoxygen

Penalise once only in any part of the mechanism for a line and twodots to show a bond

NB The arrows here are double-headed

Max 3 of any 4 marks for wrong organic reactant or wrong organicproduct (if shown)

Accept the correct use of “sticks”4

[11]

(a) Ca(OH)2 OR Mg(OH)2

Ignore name

Could be ionic1

3


(b) NaF or sodium fluoride

OR

NaCl or sodium chloride

Either formula or name can score

Do not penalise the spelling “fluoride”

When both formula and name are written,

• penalise contradictions

• if the attempt at the correct formula is incorrect, ignore it and credit correct name for the mark unless contradictory

• if the attempt at the correct name is incorrect, ignore it and credit correct formula for the mark unless contradictory

1

(c) NaClO OR NaOCl

Ignore name (even when incorrect)

The correct formula must be clearly identified if an equation iswritten

1

(d) Br2 (ONLY)

Only the correct formula scores;

penalise lower case “b”, penalise upper case “R”, penalisesuperscript

Ignore name

The correct formula must be clearly identified if an equation iswritten

1

(e) M1 S OR S8 OR S2

M2 I2 (ONLY)

Ignore names

penalise lower case “i” for iodine,

penalise superscripted numbers

Mark independently

The correct formula must be clearly identified in each case if anequation is written

2


(f) (i) CH3CH2CH=CH2

Structure of but-1-ene. Ignore name

Credit “sticks” for C-H bonds1

(ii) CH3CH2CH2CH2OH

Structure of butan-1-ol. Ignore name


(iii) CH3CH2CH3

Structure of propane. Ignore name

Ignore calculations and molecular formula

Credit “sticks” for C-H bonds

Ignore the molecular ion1

(iv) CH3CH2Br OR C2H5Br

Structure of bromoethane.

Ignore name and structure of nitrile


[10]

(a) Pentan-2-one

ONLY but ignore absence of hyphens1

(b) Functional group (isomerism)

Both words needed1

4

(c) (i)

Award credit provided it is obvious that the candidate is drawing theZ / cis isomer

The group needs to be CHOHCH3 but do not penalise poor C–Cbonds or absence of brackets around OH

Trigonal planar structure not essential1

(ii) Restricted rotation (about the C=C)

OR

No (free) rotation (about the C=C)1


(d)

M1 Tollens’ (reagent)

(Credit ammoniacal silver nitrate ORa description of making Tollens’)

(Do not credit Ag+, AgNO3 or

[Ag(NH3)2+] or “the silver mirror test”on their own, butmark M2 and M3)

M1 Fehling’s (solution) / Benedict’s

(Penalise Cu2+(aq) or CuSO4 butmark M2 and M3)

M2 silver mirror

OR black solid or black precipitate

M2 Red solid/precipitate

(Credit orange or brown solid)

M3 (stays) colourless

OR

no (observed) change / no reaction

M3 (stays) blue

OR

no (observed) change / no reaction

If M1 is blank CE = 0, for the clip

Check the partial reagents listed and if M1 has a totally incorrectreagent, CE = 0 for the clip

Allow the following alternatives

M1 (acidified) potassium dichromate(VI) (solution); mark on fromincomplete formulae or incorrect oxidation state

M2 (turns) green

M3 (stays) orange / no (observed) change / no reaction

OR

M1 (acidified) potassium manganate(VII) (solution);

mark on from incomplete formulae or incorrect oxidation state

M2 (turns) colourless

M3 (stays) purple / no (observed) change / no reaction

In all cases for M3

Ignore “nothing (happens)”

Ignore “no observation”3

(e) (i) Spectrum is for Isomer 1

or named or correctly identified

The explanation marks in (e)(ii) depend on correctly identifyingIsomer 1.

The identification should be unambiguous but candidates shouldnot be penalised for an imperfect or incomplete name. They maysay “the alcohol” or the “alkene” or the “E isomer”

1


(ii) If Isomer 1 is correctly identified, award any two from

• (Strong / broad) absorption / peak in the range3230 to 3550 cm–1 or specified value in this rangeor marked correctly on spectrumand(characteristic absorption / peak for) OH group /alcohol group

• No absorption / peak in range 1680 to 1750 cm–1 orabsence marked correctly on spectrumand(No absorption / peak for a) C=O group / carbonyl group / carbon-oxygendouble bond

• Absorption / peak in the range 1620 to 1680 cm–1

or specified value in this range or marked correctlyon spectrumand

(characteristic absorption / peak for) C=C group/ alkene / carbon-carbon double bond

If 6(e)(i) is incorrect or blank, CE=0

Allow the words “dip” OR “spike” OR “trough” OR “lowtransmittance” as alternatives for absorption.

Ignore reference to other absorptions e.g. C-H, C-O2

[10]

(a) (i) 3-bromo-3-methylpentane ONLY

Must be correct spelling but ignore hyphens and commas1

5

(ii) Electrophilic addition (reaction)

Both words needed

Accept phonetic spelling1

(iii) M1 Displayed formula of 2-bromo-3-methylpentane

All the bonds must be drawn out but ignore bond angles

M2 Position(al) (isomerism)

Do not forget to award this mark2


(iv) Structure of (E)-3-methylpent-2-ene

The arrangement of groups around the double bond must be clearwith the ethyl group attached in the correct order. Ignore bondangles.

Accept C2H5 for ethyl

Be lenient on C ─ C bonds. The main issue here is whether theyhave drawn an (E) isomer.

Accept “sticks” for C ─ H bonds and correct skeletal formula1

(b) (i) M1 R is represented by Spectrum 2

M2 Spectrum 2 shows an infrared absorption/spike/dip/trough/peak with any value(s)/range within the range 1620 to1680 (cm–1) OR this range quoted/identified and thisis due to C=COR this information could be a correctly labelled absorptionon the spectrum

OR Spectrum 1 does not have an infrared absorption in range1620 to 1680 (cm–1) and does not contain C=C.

Award M1 if it is obvious that they are referring to the secondspectrum (or the bottom one)

M2 depends on a correct M1

Ignore other correctly labelled peaks

Ignore reference to “double bond” or “alkene”2

(ii) Functional group (isomerism)1

(iii) Cyclohexane

OR

Methylcyclopentane etc.

Named correctly

Ignore structures and ignore numbers on the methyl group ofmethylcyclopentane

1

[9]

(a) Contains a C=C OR a double bond16


(b) Electrophilic addition

Both words needed1

Mechanism:

Ignore partial negative charge on the double bond.

M2 Penalise partial charges on bromine if wrong way and penaliseformal charges

Penalise once only in any part of the mechanism for a line and twodots to show a bond.

M1 Must show an arrow from the double bond towards oneof the Br atoms on a Br-Br molecule.

Deduct 1 mark for sticks.

M2 Must show the breaking of the Br-Br bond.

M3 Is for the structure of the secondary carbocation with Br substituent.

M4 Must show an arrow from the lone pair of electrons on anegatively charged bromide ion towards the positivelycharged carbon atom.

Deduct 1 mark for wrong reactant, but mark consequentially.If HBr, mark the mechanism consequentially and deduct one markIf but-1-ene, mark the mechanism consequentially and deduct onemark.If both HBr and but-1-ene, mark the mechanism consequentiallyand deduct ONLY one mark.

4

(c) (i) M1 Compounds with the same structural formula

Penalise M1 if “same structure”Ignore references to “same molecular formula” or “same empiricalformula”

1

M2 With atoms/bonds/groups arranged differently in spaceORatoms/bonds/groups have different spatialarrangements/ different orientation.

Mark independently.1


(ii)

Award credit provided it is obvious that the candidate is drawing thetrans isomer.

Do not penalise poor C–C bonds

Trigonal planar structure not essential1

[9]

(a) (i)

7

(ii) restricted rotation OR no rotation OR cannot rotate (1)3

(b) (i) Mechanism:

M1 and M2 independent

Curly arrows must be from a bond or a lone pair

Do not penalise sticks

Penalise M1 if

Penalise incorrect δ+ δ– for M2

Penalise + on C atom for M2

Only allow M1 for incorrect haloalkane

Role of the hydroxide ion: nucleophile (1) electron pair donor lone pair donor

NOT nucleophilic substitution

precedes (penalise this once)


(ii) Mechanism:

Only allow M1 and M2 for incorrect haloalkane unless RE on (i)

+ charge on H on molecule, penalise M1

M3 independentM2 must be to correct C–C

M1 must be correct H atom

Credit M1 and M2 via carbocation mechanism

No marks after any attack of C by OH–

Role of the hydroxide ion: base (1) proton acceptor accepts H+

7

[10]

C

[1]8


Z-Retinal, shown in the diagram, is a component in vitamin ...

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