14.2. Alkenes
A subsection of Chemistry, 9701, through 14. Hydrocarbons
Listing 10 of 191 questions
The structure of H is shown. C C H CH2OH CH3 CH3 CH3 H reacts with both cold, dilute, acidifi ed potassium manganate(and with hot, concentrated, acidifi ed potassium manganate(. Give the structure of the organic product of the reaction of H with cold, dilute, acidifi ed potassium manganate(. Give the structures of the organic products of the reaction of H with hot, concentrated, acidifi ed potassium manganate(. Complete the reaction scheme to show the mechanism of the reaction of H with bromine to form J. Include all necessary curly arrows, lone pairs and charges. C C CH2OH CH3 Br δ+ Br δ– CH3 CH3 C CH3 C J CH3 Br CH3 CH2OH Br Explain the origin of the dipole on the bromine molecule. J is formed as an equimolar mixture of isomers. State the type of isomerism shown by J. Draw the structures of the two isomers of J.
9701_s15_qp_23
THEORY
2015
Paper 2, Variant 3
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Proteins are formed by the polymerisation of amino acids. State the type of chemical reaction used to form these polymer chains. The amino acids serine and valine can combine together to form a dipeptide. serine, ser OH O H2N OH valine, val H2N OH O Draw the skeletal structure of the dipeptide ‘val-ser’. Suggest how the type of amino acids in a protein determines its three-dimensional structure. Using labelled diagrams or words as appropriate, explain why a particular enzyme may only catalyse a specifi c reaction on a specifi c substrate, how non-competitive inhibition of an enzyme-catalysed reaction can occur.
9701_s15_qp_41
THEORY
2015
Paper 4, Variant 1
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Proteins are formed by the polymerisation of amino acids. State the type of chemical reaction used to form these polymer chains. The amino acids serine and valine can combine together to form a dipeptide. serine, ser OH O H2N OH valine, val H2N OH O Draw the skeletal structure of the dipeptide ‘val-ser’. Suggest how the type of amino acids in a protein determines its three-dimensional structure. Using labelled diagrams or words as appropriate, explain why a particular enzyme may only catalyse a specifi c reaction on a specifi c substrate, how non-competitive inhibition of an enzyme-catalysed reaction can occur.
9701_s15_qp_43
THEORY
2015
Paper 4, Variant 3
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A reaction sequence is shown. H3C CH2 Br bromoethane H3C CH2 OH ethanol H2C CH2 ethene reaction reaction reaction 1 H3C CH2 CN propanenitrile propanoic acid H3C CH2 C O OH W reaction 3 LiAl H4 reaction 2 Complete the diagram to show the mechanism of reaction 1. Include all necessary charges, partial charges, lone pairs and curly arrows. H3C C H H Br H3C C H H CN + –CN Give the name of the type of reaction involved in reaction 3. The infra-red spectrum of the propanoic acid produced by reaction 2 is shown. transmittance wavenumber / cm–1 Describe and explain the main difference between the infra-red spectrum of W and that of propanoic acid. Reactions 4 and 5 use the same reagent. Give the reagent and conditions needed for reaction 4. reagent conditions Give the conditions needed for reaction 5. Under appropriate conditions, ethanol and propanoic acid undergo a condensation reaction. State the condition necessary for the reaction. Draw the skeletal formula of the organic product of this reaction. Name the organic product of this reaction. Question 5 continues over the page. V reacts with acidified manganate(ions in two different ways depending on the conditions, as shown in the reaction sequence below. propanoic acid H3C CH2 C V T O OH hot, concentrated MnO4 – / H+ cold, dilute MnO4 – / H+ V decolourises bromine water. When the acidified manganate(is hot and concentrated, propanoic acid is the only organic product. When the acidified manganate(is cold and dilute, the organic product is T which has two chiral centres. Give the structural formulae of V and T. V T Identify the types of stereoisomerism shown by V and T. V T
9701_s16_qp_21
THEORY
2016
Paper 2, Variant 1
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A reaction sequence based on propan-1-ol is shown. CH3CH CH2 CH3CH2CH2 CH3CH2CH2 OH Br CH3CH2C OH O CH3CH2C H O CH3CH2C CN H OH reaction 1 reaction 4 propan-1-ol reaction 5 NaCN / H+ reaction 3 reaction 2 Reactions 1 and 2 can both be carried out using the same reagents. Identify suitable reagents for reactions 1 and 2. State and explain how the reaction should be carried out to ensure that reaction2 rather than reaction1 occurs. Identify the necessary reagents and conditions for each of reactions 3 and 4. reaction 3 reaction 4 Complete the reaction mechanism for reaction 5. Include all relevant lone pairs, curly arrows, charges and partial charges. CH3CH2 C CH3CH2 CN H OH O C H NC− The product of reaction 5 exhibits stereoisomerism. Draw the two stereoisomers in the conventional way. Suggest why a mixture of the two stereoisomers is formed by reaction 5.
9701_s16_qp_22
THEORY
2016
Paper 2, Variant 2
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P, Q and R all have the molecular formula C3H6O. They are all structural isomers of each other. P and Q each contain an oxygen atom bonded directly to a carbon atom that is sp2 hybridised. R contains an oxygen atom bonded directly to a carbon atom that is sp3 hybridised. Explain the meaning of the term structural isomers. Explain how sp2 and sp3 hybridisation can occur in carbon atoms. sp2 hybridisation sp3 hybridisation State the bond angles normally associated with each type of hybridisation in carbon atoms. sp2 sp3 R contains two different functional groups, one of which is an alkene group. R reacts with cold, dilute, acidified manganate(ions to form propane-1,2,3-triol. H HO C H OH OH C propane-1,2,3-triol H H C H Give the displayed formula of R. State the type of reaction and what you would observe when R reacts with bromine water. Draw the structure of the product formed when R reacts with bromine water. Identify the gaseous product formed when R reacts with hot, concentrated, acidifiedmanganate(ions. P and Q (C3H6O) both form an orange precipitate when reacted with 2,4-DNPH. Only Q produces a yellow precipitate when reacted with alkaline aqueous iodine. Name P and Q. P Q Identify the yellow precipitate formed by the reaction of Q with alkaline aqueous iodine. P and Q each react with hydrogen cyanide to form a single product. The product formed from P exists as a pair of optical isomers. The product formed from Q does not exhibit optical isomerism. Explain the meaning of the term optical isomers. Ethanal, CH3CHO, also reacts with hydrogen cyanide. The product of this reaction is CH3CH(OH)CN. Draw the mechanism of this reaction. Include all necessary charges, dipoles, lone pairs and curly arrows.
9701_s17_qp_21
THEORY
2017
Paper 2, Variant 1
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Questions Discovered
191