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Date May 2017 Marks available 2 Reference code 17M.3.hl.TZ2.20
Level HL Paper 3 Time zone TZ2
Command term Suggest Question number 20 Adapted from N/A

Question

Aspirin is one of the most widely used drugs in the world.

Aspirin was synthesized from 2.65 g of salicylic acid (2-hydroxybenzoic acid) (Mr = 138.13) and 2.51 g of ethanoic anhydride (Mr = 102.10).

Suggest two absorbances, other than the absorbances due to the ring structure and C–H bonds, that would be present in the infrared (IR) spectrum of aspirin.

[2]
a.iii.

State two techniques, other than IR spectroscopy, which could be used to confirm the identity of aspirin.

[2]
a.iv.

Markscheme

Any two of:

2500–3000 «cm–1» / «absorbance» due to O–H in carboxyl

1700–1750 «cm–1» / «absorbance» due to C=O in carboxyl/ethanoate

1050–1410 «cm–1» / «absorbance» due to C–O bond in carboxyl/ethanoate

 

Accept “carboxylic acid” for “carboxyl”, “acetate/ester” for “ethanoate”.

Accept specific wavenumber once within indicated range.

Do not award mark if reference is made to an alcohol/ether.

[2 marks]

a.iii.

Any two of:

melting point

mass spectrometry/MS

high-performance liquid chromatography/HPLC

NMR/nuclear magnetic resonance

X-ray crystallography

elemental analysis

 

Accept “spectroscopy” instead of “spectrometry” where mentioned but not “spectrum”.

Accept “ultraviolet «-visible» spectroscopy/UV/UV-Vis”.

Do not accept “gas chromatography/GC”.

Accept “thin-layer chromatography/TLC” as an alternative to “HPLC”.

[2 marks]

a.iv.

Examiners report

[N/A]
a.iii.
[N/A]
a.iv.

Syllabus sections

Core » Topic 10: Organic chemistry » 10.1 Fundamentals of organic chemistry
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Core » Topic 11: Measurement and data processing » 11.3 Spectroscopic identification of organic compounds
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