DP Chemistry (last assessment 2024)

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Question 19M.3.hl.TZ1.19

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Date May 2019 Marks available [Maximum mark: 5] Reference code 19M.3.hl.TZ1.19
Level hl Paper 3 Time zone TZ1
Command term Deduce, Identify, Name Question number 19 Adapted from N/A
19.
[Maximum mark: 5]
19M.3.hl.TZ1.19

Aspirin can be obtained from salicylic acid.

(a)

Unreacted salicylic acid may be present as an impurity in aspirin and can be detected in the infrared (IR) spectrum.

Name the functional group and identify the absorption band that diff erentiates salicylic acid from aspirin. Use section 26 of the data booklet.

Name:

Absorption band:

[2]

Markscheme

Name:
hydroxyl   [✔]

Absorption band:
3200–3600 «cm–1»  [✔]

 

Note: Accept “phenol” OR “alcohol” but not “hydroxide”. 

Examiners report

Many candidates scored a mark for naming a functional group that differentiates salicylic acid from aspirin. Some incorrectly said ether or carboxylic acid. Many candidates also scored for identifying the absorption band although 1700-1750 was a popular incorrect answer.

Additional information can be obtained from the 1H NMR spectrum of aspirin.

(b(i))

Deduce the protons responsible for signals X and Y by marking them on the structure of aspirin in (a). Use section 27 of the data booklet.

[2]

Markscheme

correct X   [✔]
correct Y   [✔]

 

Note: X and Y must be near the Hs.

Examiners report

There was considerable confusion with indicating protons responsible for 1H NMR signals. Often entire functional groups were circled or carbon atoms and not hydrogen atoms were circled.

(b(ii))

Identify the splitting pattern of signals X and Y.

 

X:

Y:

[1]

Markscheme

X: singlet AND Y: singlet  [✔]

Examiners report

There was also great difficulty in identifying the splitting pattern of the signals. It was rare to see both signals identified as singlets.

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