| Date | November 2018 | Marks available | 2 | Reference code | 18N.3.hl.TZ0.21 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 21 | Adapted from | N/A |
Question
Taxol is a chiral cancer drug which is synthesized using a chiral auxiliary.
The diagram shows part of a Taxol molecule in skeletal form.
Draw a circle around each chiral carbon.
Outline how chiral auxiliaries are used to synthesize the desired enantiomer.
Explain the process of solvent extraction by which Taxol is isolated.
Markscheme
Do not penalize any other notation (eg *) used for a circle.
chiral auxiliary creates stereochemical condition necessary to follow a certain pathway
OR
stereochemical induction
OR
existing chiral centre affects configuration of new chiral centres ✔
chiral molecule/auxiliary/optically active species is used/added/connected to the starting molecule «to force reaction to follow a certain path»
OR
«after new chiral centre created» chiral auxiliary removed «to obtain desired product» ✔
Any two of:
immiscible solvents ✔
partitioning of Taxol between the two solvents
Taxol more soluble in one solvent ✔
extraction carried out multiple times «to improve extraction» ✔
shaking/stirring the mixture ✔
separating the two layers ✔
evaporation of the solvent from the final solution «to obtain pure Taxol» ✔
Examiners report
Syllabus sections
- 16N.3.hl.TZ0.26c: Omeprazole exists as a racemic mixture whereas esomeprazole is a single enantiomer. Outline...
- 18N.3.hl.TZ0.21c: Explain the process of solvent extraction by which Taxol is isolated.
-
17M.3.hl.TZ1.28b:
A mixture of enantiomers shows optical rotation.
Suggest a conclusion you can draw from this data.
-
19M.3.hl.TZ1.25a:
Identify the chiral carbon atom using an asterisk, *.
-
17N.3.hl.TZ0.23b:
Explain the role of the chiral auxiliary in the synthesis of Taxol.
- 19N.3.hl.TZ0.26a: State the feature of Taxol that is a major challenge in its synthesis. Use section 37 of the...
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19M.3.hl.TZ1.25b:
Enantiomers can be identified using a polarimeter. Outline how this instrument differentiates the enantiomers.
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18N.3.hl.TZ0.21a:
The diagram shows part of a Taxol molecule in skeletal form.
Draw a circle around each chiral carbon.
-
18M.3.hl.TZ1.16e:
Many drugs are chiral. Explain how a polarimeter can be used to determine the relative proportion of two enantiomers.
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19M.3.hl.TZ2.25b:
Outline the operation of a polarimeter used to distinguish between enantiomers.
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18M.3.hl.TZ2.25:
Taxol was originally obtained from the bark of the Pacific yew tree.
Outline how Green Chemistry has improved the process of obtaining Taxol.
-
19N.3.hl.TZ0.26b:
Describe how the challenge in (a) was resolved by pharmaceutical companies.
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17M.3.hl.TZ2.25:
Taxol is produced using a chiral auxiliary. Describe how the chiral auxiliary functions to produce the desired product.
- 20N.3.hl.TZ0.19d: Circle two chiral carbons in the section of the Taxol structure below.
