Question 18N.3.hl.TZ0.21
| Date | November 2018 | Marks available | [Maximum mark: 5] | Reference code | 18N.3.hl.TZ0.21 |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Draw, Explain, Outline | Question number | 21 | Adapted from | N/A |
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.
[1]
Do not penalize any other notation (eg *) used for a circle.
Outline how chiral auxiliaries are used to synthesize the desired enantiomer.
[2]
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» ✔
Explain the process of solvent extraction by which Taxol is isolated.
[2]
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» ✔