JPJC 2026 Introduction to Organic Chemistry, Alkanes, Alkenes Revision

1 2026 JC1 H2 Chemistry (9476) Topical Revision for Organic Chemistry Topics: Introduction to Organic Chemistry, Alkanes & Alkenes FOUNDATION KIT Multiple-Choice Questions Introduction to Organic Chemistry [PJC Promo 2013/P1/Q16] 1 The thyroid gland concentrates iodine and uses it to produce thyroxine, which is a hormone that controls the metabolic rate. OH I I O I I C C N H C O OH H H H H p q r s thyroxine What are the values, to the nearest degree, of the bond angles p, q, r and s? p q r s A 180o 90o 180o 90o B 105o 110o 107o 120o C 180o 90o 120o 180o D 105o 90o 107o 180o [PJC Promo 2013/P1/Q17] 2 Which of the following gives the correct number of  and  bonds present in the following molecule shown below? CH2 C C CH3 O OH Number of  bonds Number of  bonds A 5 2 B 7 0 C 11 2 D 13 0

2 [PJC Promo 2010/P1/Q16] 3 How many esters are there with the molecular formula C4H8O2? A 2 B 3 C 4 D 5 [PJC Promo 2011/P1/Q19] 4 The drug cortisone has the formula shown. O CH3 CH3 OHC CH2OH O O How many chiral centres are there in one molecule of cortisone? A 4 B 5 C 6 D 7 [PJC Promo 2012/P1/Q13] 5 Many drugs show enantiomerism. The diagrams below show the structure of three drugs. What is the total number of chiral carbon centres in these three structures? N C OH CH2 N CH2CH3 CH2CH3 lidocaine CH2 C CH3 H NH2 amphetamine N H O N O O CH3 H phenobarbital derivative A 1 B 2 C 3 D 4

3 [PJC Promo 2013/P1/Q18] 6 Which of the following structures does not exhibit enantiomerism? A CH3 CH2CH3 Br B CH3 CH3 CH2 C NH NH O CH3 O O D NH2 NH2NH2 [PJC Promo 2010/P1/Q17] 7 The diagram shows the structure of the insect attractant methoprene. C CH3 CH2 CH2 CH2 CH CH3 CH2 C H C C C C O O CH CH3 CH3 CH3 H H OCH3 CH3 What is the total number of stereoisomers ( both cis-trans isomers and enantiomers) of this molecule? A 2 B 4 C 8 D 16

4 Alkanes [PJC Prelim 2010/P1/Q19] 8 Which of the following is a propagation step in the reaction between propane and chlorine when they are irradiated with ultraviolet light? A CH3CH2CH2 + Cl• → CH3CH2CH2Cl B CH3CH2CH2Cl + Cl• → CH3CH2CH2 + Cl2 C CH3CH2CHCl + Cl2 → CH3CH2CHCl2 + Cl• D CH3CH2CH2 + Cl2 → CH3CH2CHCl + HCl [PJC Promo 2011/P1/Q18] 9 Why does the reaction between propane and chlorine not give a high yield of 2-chloropropane? A A mixture of chlorine and propane cannot be prevented from exploding. B Disubstitution by chlorine takes place preferentially to monosubstitution. C The central carbon atom of propane is too weakly nucleophilic. D The chlorine replaces any of the hydrogen atoms in propane. [PJC Prelim 2013/P1/Q22] 10 Ethane reacts with bromine in the presence of ultraviolet light to form a mixture of products. Which of the following about the reaction mechanism is incorrect? A Both initiation and propagation steps involve homolytic fission. B Both initiation and propagation steps produce bromine atoms. C Both propagation and termination steps produce hydrogen bromide molecules. D Both propagation and termination steps involve C−Br bond formation. [PJC Promo 2012/P1/Q15] 11 How many dichlorinated constitutional (structural) isomers can be formed by the chlorination of pentane in the presence of sunlight? A 6 B 7 C 8 D 9 [PJC JC2 MYE 2010/P1/Q19] 12 Pentane was reacted with limited bromine in the presence of uv light. Assume that only mono-bromination takes place and the reaction occurs at the same rate at all carbon atoms. What is the ratio of the products obtained? 1-bromopentane 2-bromopentane 3-bromopentane A 3 2 1 B 1 2 3 C 1 3 2 D 3 1 2 • • • • •

5 [HCI Prelim 2017/P1/Q15] 13 When heated with chlorine, the following hydrocarbon undergoes free radical substitution. In the propagation step, the free radical Q• is formed by the loss of one hydrogen atom. Ignoring any stereoisomers, how many different forms of Q• are theoretically possible? A 3 B 4 C 6 D 8 [RI Prelim 2017/P1/Q29] 14 Deuterium, D, is a heavy isotope of hydrogen. 1,3 -Dideuteriopropane is reacted with limiting chlorine under UV light, so that monochlorination takes place. 1,3-dideuteriopropane Assuming that a C –D bond is broken as easily as a C –H bond, what proportion of the monochlorinated products will contain a chiral centre? A 33% B 40% C 50% D 66% [RVHS Prelim 2020/P1/Q24] 15 In the reaction of methylpropane with chlorine under ultraviolet light, which of the following compounds can be formed? 1 2 3 A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

6 Alkenes [PJC Prelim 2010/P1/Q20] 16 Fly paper is used as a non-toxic method of trapping houseflies. To increase its effectiveness, Muscalure, which is a fly pheromone, is added to the paper during its manufacture. Muscalure has the following structure. CH3(CH2)7CH=CH(CH2)12CH3 Which of the following statement about Muscalure is not correct? A It decolourises aqueous bromine. B It does not rotate plane polarised light. C It reacts with HBr(g) to give a chiral product. D It will turn orange acidified potassium dichromate(VI) green. [PJC Prelim 2011/P1/Q20] 17 Compound M (C6H8) gives compound N (C4H6O4) on oxidation. One mole of M reacts with two moles of hydrogen gas in the presence of platinum catalyst. Which of the following shows the structure of M? A B CH2=CHCH=CHCH=CH2 C CH2=CHCH2CH2CH=CH2 D CH2 [PJC Promo 2013/P1/Q22] 18 The following compound is a derivative of -Candinene which can be found in Juniper berries. Cl What is the total number of stereoisomers for the major product formed after the above compound has reacted with excess hydrogen bromide at room temperature? A 16 B 32 C 64 D 128

7 [PJC Prelim 2012/P1/Q17] 19 Reaction of ethene with bromine in the presence of aqueous sodium chloride gives a mixture of products. Which pair of products will be included in this mixture? A CH2(OH)CH2Br and CH2ClCH2OH B CH2BrCH2Br and CH2ClCH2Br C CH2BrCH2Br and CH2ClCH2Cl D CH2BrCH2Br and CH2(OH)CH2Cl [PJC Promo 2013/P1/Q23] 20 Deuterium, D, is the isotope of hydrogen. What is the maximum number of deuterium atom(s) that can be incorporated into a molecule of Linalo-ol when it reacts with bromine in heavy water, D2O? C CCH3 CH3 C C C OH CH3 C CH2 H H H H H H Linalo-ol A 1 B 2 C 3 D 4 [PJC JC2 MYE 2011/P1/Q21] 21 Under suitable conditions, ethene may undergo a reaction with an interhalogen compound, ICl. Which of the following shows the structure of the intermediate formed? A [CH3CH2]+ B [CH3CHI ]+ C [CH2CH2I ]+ D [CH2CH2Cl]+ [PJC Prelim 2012/P1/Q16] 22 Which hydrocarbon, on treatment with hot acidified potassium manganate( VII), would give ethanoic acid only? A CH3CH=CH2 B CH3CH=CHCH3 C C(CH3)2=CHCH3 D C(CH3)2=C(CH3)2

8 [PJC Prelim 2010/P1/Q20] 23 When Br2 adds to propene CH3CH=CH2 + Br2 → CH3CHBrCH2Br the reaction pathway diagram is as follows. Which point in the diagram represents a positively charged intermediate? [HCI Prelim 2017/P1/Q16] 24 Compound W is heated with excess acidified KMnO4 for a prolonged period. compound W Which of the following compounds is least likely to be a product of this reaction? A CO2 B C D A B C D

9 Structured & Free-response Questions Introduction to Organic Chemistry [PJC Promo 2013/P2/Section A/Q4] 1 Citronellal is a component found in many essential oils. It has a distinct lemon scent and is commonly used as a flavouring agent. It has the structural formula as shown below. (a) In the space below, name and sketch the shape of the hybrid orbitals around the carbon ato