JPJC 2026 Intro to Organic Chemistry and Isomerism MCQ Answer

2026 JPJC JC1 H2 Chemistry (9476) 1 JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 Chemistry (9476) MCQ Quiz Topic 8: Introduction to Organic Chemistry and Isomerism Answers: 1 2 3 4 5 B D C A C 1 Which of the following structures does not exhibit enantiomerism? A B C D Answer: B A molecule exhibits enantiomerism (i.e. it is a chiral molecule) if it has: (1) chiral carbon (i.e. asymmetric C bonded to 4 different groups of atoms); (2) no plane of symmetry. For the molecules which exhibit enantiomerism , the chiral centre(s) are marked with an asterisk (*). A ✓B The C labelled with # is NOT chiral because it does not have 4 different group of atoms attached to it. The two groups attached to the C# (in clockwise & anti −clockwise direction) are identical. C D CH3 CH2CH3 Br O O O CH3 CH3 CH3 CH2 NH2 NH2NH2 CH3 CH2CH3 Br * O O O CH3 # * CH3 CH3 CH2 * NH2 NH2NH2 *

2026 JPJC JC1 H2 Chemistry (9476) 2 2 Aureomycin is a powerful antibiotic and it has the structure as shown below. aureomycin What functional groups are present in the molecular structure of aureomycin? 1 alcohol 2 amine 3 alkene A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 Answer: D (1, 2 and 3) OH Cl O OH CH3 OH OH O H N CH3 CH3 C O NH2 OH OH O OH O NH2 O CH3OH H N CH3 CH3 Cl alcohol amine alkene OH

2026 JPJC JC1 H2 Chemistry (9476) 3 3 Covalent bonds are formed by orbital overlap. The shape of unsaturated hydrocarbon molecules can be explained in terms of hybridisation of orbitals. Which bond is not present in the molecule shown below? A a  bond formed by 2p−2p overlap B a  bond formed by 1s−2sp2 overlap C a  bond formed by 2sp−2s overlap D a  bond formed by 2sp2−2sp3 overlap Answer: C The sp hybridised carbons are C1, C2 and C4. The sp2 hybridised carbons are C3 and C5. The sp3 hybridised carbon is C6. ✓A Between C1−C2, C3−C4 and C4−C5 bonds,  bonds are formed by 2p−2p overlap. ✓B Between C3−H and C5−H bonds,  bonds are formed by 1s−2sp2 overlap. C H only has 1s orbital and all 2s orbital of C must be hybridised. Hence,  bond formed by 2sp−2s overlap is not present. ✓D Between C5−C6,  bonds are formed by 2sp2−2sp3 overlap. C CH C H C C H C H H H C CH C H C C H C H H H 1 2 3 4 5 6

2026 JPJC JC1 H2 Chemistry (9476) 4 4 Three statements were made about the structure and functional groups of compound P. Compound P Which statements about compound P are correct? 1 It contains three chiral centres. 2 It contains 16 stereoisomers. 3 It contains a benzene ring. A 1 only B 1 and 2 only C 2 and 3 only D 1, 2 and 3 Answer: A (1 only) ✓1 It contains three chiral centres (see * indicated). 2 It contains 23 = 8 stereoisomers, not 16. 3 It contains cyclohexene, NOT benzene. 5 What is the IUPAC name of compound J? compound J A 5-hydroxyhex-3-ene B 2-hydroxyhex-3-ene C hex-3-en-2-ol D hex-3-en-5-ol OH OH CH(OH)CH2OH OH OH CH(OH)CH2OH * * *