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Date November 2017 Marks available 1 Reference code 17N.2.hl.TZ0.8
Level HL Paper 2 Time zone TZ0
Command term State Question number 8 Adapted from N/A

Question

The reactivity of organic compounds depends on the nature and positions of their functional groups.

The structural formulas of two organic compounds are shown below.

Deduce, giving a reason, which of the two compounds can show optical activity.

[1]
a.iv.

Draw three-dimensional representations of the two enantiomers.

[1]
a.v.

State the reagents used in the nitration of benzene.

[1]
c.

State an equation for the formation of NO2+.

[1]
d.

Explain the mechanism of the reaction between 2-bromo-2-methylpropane, (CH3)3CBr, and aqueous sodium hydroxide, NaOH (aq), using curly arrows to represent the movement of electron pairs.

[4]
e.

Markscheme

A AND it has a chiral centre/asymmetric carbon atom/carbon with 4 different substituents

a.iv.

Accept structures without tapered bonds.

a.v.

concentrated HNO3 AND concentrated H2SO4

“concentrated” must occur at least once (with either acid).

c.

HNO3 + 2H2SO4 H3O+ + NO2+ 2HSO4

Accept: HNO3 + 2H2SO4   NO2+ HSO4– + H2O.

Accept: HNO3 + 2H2SO4    H2NO3+ + HSO4.

Accept single arrow instead of equilibrium sign.

Accept equivalent two step reactions in which sulfuric acid first behaves as strong acid and protonates nitric acid, before behaving as dehydrating agent removing water from it.

d.

curly arrow showing Br leaving

representation of tertiary carbocation

curly arrow going from lone pair/negative charge on O in OH to C+

formation of (CH3)3COH AND Br

Do not accept curly arrow originating from C of C–Br bond.

Do not accept arrow originating on H in OH.

Accept Br anywhere on product side in the reaction scheme.

Award [2 max] for an SN2 type mechanism.

e.

Examiners report

[N/A]
a.iv.
[N/A]
a.v.
[N/A]
c.
[N/A]
d.
[N/A]
e.

Syllabus sections

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