DP Chemistry (last assessment 2024)

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Question 19N.3.hl.TZ0.21a

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Date November 2019 Marks available [Maximum mark: 3] Reference code 19N.3.hl.TZ0.21a
Level hl Paper 3 Time zone TZ0
Command term Explain Question number a Adapted from N/A
a.
[Maximum mark: 3]
19N.3.hl.TZ0.21a

Codeine, morphine and diamorphine (heroin) are derived from opium.

(a)

Explain why diamorphine has greater potency than morphine.

[3]

Markscheme

Any three of:
morphine has «two» hydroxyl «groups» AND diamorphine has «two» ester/ethanoate/acetate «groups» ✔

NOTE: Accept “heroin” for “diamorphine”.
Accept formulas.
Accept “hydroxy” for “hydroxyl” but not “hydroxide”.
Accept “acyl” for “ester «groups»”.

 

morphine is more polar than diamorphine
OR
groups in morphine are replaced with less polar/non-polar groups in diamorphine ✔

NOTE: Do not accept just “diamorphine is non-polar” for M2.

 

morphine is «more» soluble in blood «plasma»
NOTE: Accept “water” for “blood”.
OR
diamorphine is «more» soluble in lipids
NOTE: Accept “fats” for “lipid”.
OR
diamorphine is more soluble in non-polar environment of CNS/central nervous system than morphine ✔

 

diamorphine crosses the blood–brain barrier/BBB «easily» ✔

 

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