JPJC 2026 Alkene MCQ Answer

2026 JPJC JC1 H2 Chemistry (9476) 1 [Turn Over JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 Chemistry (9476) MCQ Quiz Topic 10: Alkenes Name : __________________________________________ 5 Class : 26S ___ Date : ____________ Duration : 10 minutes 1 Which of the following transformation has the correct reaction conditions? [(alc) indicates the compound is in an alcohol solvent.] A CH3CH2CH=CH2(l) + HI(aq) CH3CH2CHICH3 For electrophilic addition of HI, HI should be dry. Cannot be in aqueous medium. B CH3CH2CHBrCH3(alc) + NaOH(alc) CH3CH=CHCH3 + NaBr + H2O Elimination. Required conditions are alcoholic NaOH (or NaOH in alcohol) , heat . HBr is eliminated between adjacent carbons to form a C=C bond. The by-products, NaBr and H2O, are formed from HBr + NaOH → NaBr + H2O C CH3CH2CH=CH2(l) + KMnO4(aq) CH3CH2COOH Under cold condition, a diol will be formed (mild oxidation). To cleave C=C bond by strong oxidation, heating acidic or alkaline KMnO 4(aq) with the alkene is necessary. D CH3CH2CH=CH2(l) + Br2(CCl4) CH3CH2CHBrCH2Br Electrophilic addition of Br2 across the C=C bond should take place in the absence of UV/sunlight light. With UV/sunlight light, free-radical substitution occurs and any H atom can be replaced by Br atom. heat heat cold uv light

2026 JPJC JC1 H2 Chemistry (9476) 2 2 2-methylbuta-1,3-diene, CH 2=C(CH3)CH=CH2 is used as a monomer in the manufacture of synthetic rubbers. 2-methylbuta-1,3-diene: Which compound would not produce this monomer on heating with concentrated H3PO4? A (CH3)2C(OH)CH(OH)CH3 C C CH3 CH3 C OHOH H H H H C C CH3 C H H H CH2 B HOCH2CH(CH3)CH2CH2OH C C C H C HCH3 H H OH H C C CH3 C H H H CH2 H OH H C HOCH2CH(CH3)CH(OH)CH3 C C CH3 H C OHCH3 H H OH H C C CH3 C H H H CH2 D HOCH2C(CH3)(OH)CH2CH3 C C CH3 OH C HCH3 H H OH H C C C C H H CH3 H H H H H C C C CH3 OH CH3 H H H H C C C CH3 OH CH2 H + + H H C C C CH3 OH CH3 H

2026 JPJC JC1 H2 Chemistry (9476) 3 [Turn Over 3 When ethene reacts with ICl in the presence of aqueous NaBr, what are the possible products formed? 1 2 3 4 A 1 and 2 only B 1 and 3 only C 2 and 4 only D 3 and 4 only 4 Limonene is an oil formed in the peel of citrus fruits. H H H H H H Which of the following is the major (Apply Markovnikov’s rule: H atom is added to the C atom with more H atoms) product formed when hydrogen bromide reacts with limonene at room temperature? A B C D H C C H H H + I Cl + − H C C H H H I + + Cl - • • slow H C C H H H I + + Cl - • • fast H C CH H H I OH Br - • • H2O • • H C CH H H I Cl + + H C CH H H I Br H Br + − H Br H Br → Br Br CH3 CH3 CH3 CH3

2026 JPJC JC1 H2 Chemistry (9476) 4 5 Compound Q has the following structure. (CH3)2C=CHCH2CH=CH2 Products: What is produced when Q is treated with an excess of hot concentrated acidified KMnO4? 1 (CH3)2C(OH)CH(OH)CH2CH(OH)CH2OH 2 CH3COCH3 3 CH3CH2CO2H 4 HO2CCH2CO2H A 1 only B 2 and 4 only C 3 and 4 only D 2, 3 and 4 only C O CH3 CH3 CCH2C O HO O OH CO2 + H2O