RI Alkanes + Alkenes Remedial

Name: ………………………………………. ( ) Class: ……………. Date: ……………. Raffles Institution Year 6 H2 Chemistry 2025 Set A T1W6 – Introduction to Organic Chemistry, Alkanes and Alkenes Notes: Introduction to Organic Chemistry – Stereoisomerism 1 Identification of chiral centres. (a) (b) 2 Illustration of stereoisomers (a) CH3CH2CH(CN)COOH (b) CH3CH2CH=CHCl ⎯ Pre-ChemFocus Activity ⎯ • Familiarise yourself with the following mechanisms: Free Radical Substitution of Alkanes and Electrophilic Addition of Alkenes • To view infopack at IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T1W6 Intro to Organic Chemistry, Alkanes, Alkenes > FIRST VIDEO ONLY • • • •

Notes:

Self-Check Questions 1 How many stereoisomers are possible for the following molecule? A 8 B 16 C 32 D 64 2 When 3-methylpentane reacts with bromine, four different monobrominated products are produced. (a) A description of the reaction mechanism producing isomer D is illustrated in Fig 1.1. Correct the mechanism by annotating on the figure. Learning points: Check your answers at IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T1W6 Intro to Organic Chemistry, Alkanes, Alkenes > Remaining videos

(b) State and explain the predicted ratio of the monobrominated products of 3-methylpentane. A : B : C : D = ….. : ….. : ….. : ….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………..[3] Learning point(s): Not all primary H atoms lead to the same product. Students need to be clear in articulating which H atoms (type and on which C) leads to a certain product. 3 When 1-methylcyclobutene reacts with hydrogen bromide, two products are produced. (a) A description of the reaction mechanism producing isomer D is illustrated in Fig 2.1. Correct the mechanism by annotating on the figure. Fig. 2.1 (b) By considering the stability of the carbocation intermediate, explain why isomer F is the major product. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ..……………………………………………………………………………………………[2]

Tutorial Discussion Questions (to complete before Chemfocus session) 1a 2-methylpropane can react with bromine in the presence of sunlight to give two monobrominated products, 1-bromo-2-methylpropane and 2-bromo-2-methyl propane. (i) Predict the ratio of 1-bromo-2-methylpropane to 2-bromo-2-methylpropane. ……………………………………………………………………………………………..[1] (ii) When the chlorination is carried out and the product are analysed, it is found that the mole ratio of 1-bromo-2-methylpropane to 2-bromo-2-methylpropane formed is about 3:2. Suggest an explanation for the difference between this ratio and the one you gave in (i).