DP Chemistry (last assessment 2024)

Question 20N.2.hl.TZ0.1d(iii)

Date	November 2020	Marks available	[Maximum mark: 3]	Reference code	20N.2.hl.TZ0.1d(iii)
Level	hl	Paper	2	Time zone	TZ0
Command term	Explain	Question number	d(iii)	Adapted from	N/A

d(iii).

[Maximum mark: 3]

20N.2.hl.TZ0.1d(iii)

Chlorine undergoes many reactions.

(d(iii))

Explain the mechanism of the reaction between chloroethane and aqueous sodium hydroxide, $NaOH (aq)$ , using curly arrows to represent the movement of electron pairs.

[3]

Markscheme

curly arrow going from lone pair/negative charge on $O$ in ⁻OH to $C$ ✔

curly arrow showing $Cl$ leaving ✔

representation of transition state showing negative charge, square brackets and partial bonds ✔

Accept $O H^{-}$ with or without the lone pair.

Do not accept curly arrows originating on $H$ in $O H^{-}$ .

Accept curly arrows in the transition state.

Do not penalize if $H O$ and $C l$ are not at 180°.

Do not award M3 if $O H - C$ bond is represented.

Examiners report

Few earned full marks for the curly arrow mechanism of the reaction between sodium hydroxide and chloroethane. Mistakes being careless curly arrow drawing, inappropriate –OH notation, curly arrows from the hydrogen or from the carbon to the C–Cl bond, or a method that missed the transition state.

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Additional higher level (AHL)

Additional higher level (AHL) » Topic 20: Organic chemistry » 20.1 Types of organic reactions

Additional higher level (AHL) » Topic 20: Organic chemistry

Question 20N.2.hl.TZ0.1d(iii)

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