DP Chemistry (last assessment 2024)

Question 19N.2.hl.TZ0.3b(iii)

Date	November 2019	Marks available	[Maximum mark: 4]	Reference code	19N.2.hl.TZ0.3b(iii)
Level	hl	Paper	2	Time zone	TZ0
Command term	Apply, Sketch	Question number	b(iii)	Adapted from	N/A

b(iii).

[Maximum mark: 4]

19N.2.hl.TZ0.3b(iii)

Propene is an important starting material for many products. The following shows some compounds which can be made from propene, C₃H₆.

Propene (C₃H₆) → C₃H₇Cl → C₃H₈O → C₃H₆O

An experiment was carried out to determine the order of reaction between one of the isomers of C₃H₇Cl and aqueous sodium hydroxide. The following results were obtained.

(b(iii))

Sketch the mechanism using curly arrows to represent the movement of electrons.

[4]

Markscheme

curly arrow going from lone pair on O/negative charge on OH^– to C ✔

curly arrow showing C–Cl bond breaking ✔

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

formation of CH₃CH(OH)CH₃ AND Cl^– ✔

NOTE: Do not allow arrow originating on H in OH^–.

Allow curly arrow going from bond between C and Cl to Cl in either reactant or transition state.

Do not award M3 if OH–C bond is represented.

Accept formation of NaCl instead of Cl^–.