Propanone, $$$\mathrm{CH}_{3} \mathrm{COCH}_{3}$$$, is an important organic reagent. Fig. 4.1 shows some reactions of propanone and its derivatives. Fig. 4.1 Reaction 1 is a nucleophilic addition reaction. (i) Complete Fig. 4.2 to show the mechanism for the formation of $$$\mathbf{A}$$$ from propanone. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. Fig. 4.2 (ii) Explain why $$$\mathbf{A}$$$ does not show optical isomerism. ....................................................................................................................................... . .................................................................................................................................

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_w24_qp_23 Year：2024 Question No：4(a)

Answer:

Knowledge points:

13.2.1.1 homologous series

13.2.1.2 saturated and unsaturated

13.2.1.3 homolytic and heterolytic fission

13.2.1.4 free radical, initiation, propagation, termination (the use of arrows to show movement of single electrons is not required)

13.2.1.5 nucleophile, electrophile, nucleophilic, electrophilic

13.2.1.6 addition, substitution, elimination, hydrolysis, condensation

13.2.1.7 oxidation and reduction (in equations for organic redox reactions, the symbol [O] can be used to represent one atom of oxygen from an oxidising agent and the symbol [H] one atom of hydrogen from a reducing agent)

13.2.2.1 free-radical substitution

13.2.2.2 electrophilic addition

13.2.2.3 nucleophilic substitution

13.2.2.4 nucleophilic addition (in organic reaction mechanisms, the use of curly arrows to represent movement of electron pairs is expected; the arrow should begin at a bond or a lone pair of electrons)

13.3.1 describe organic molecules as either straight-chained, branched or cyclic

13.3.2 describe and explain the shape of, and bond angles in, molecules containing sp, sp2 and sp3 hybridised atoms

13.3.3 describe the arrangement of σ and π bonds in molecules containing sp, sp2 and sp3 hybridised atoms

13.3.4 understand and use the term planar when describing the arrangement of atoms in organic molecules, for example ethene

13.4.1 describe structural isomerism and its division into chain, positional and functional group isomerism

13.4.2 describe stereoisomerism and its division into geometrical (cis/trans) and optical isomerism (use of E, Z nomenclature is acceptable but is not required)

13.4.3 describe geometrical (cis/trans) isomerism in alkenes, and explain its origin in terms of restricted rotation due to the presence of π bonds

13.4.4 explain what is meant by a chiral centre and that such a centre gives rise to two optical isomers (enantiomers) (Candidates should appreciate that compounds can contain more than one chiral centre, but knowledge of meso compounds, or nomenclature such as diastereoisomers is not required)

13.4.5 identify chiral centres and geometrical (cis/trans) isomerism in a molecule of given structural formula including cyclic compounds

13.4.6 deduce the possible isomers for an organic molecule of known molecular formula

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