Question 19M.3.hl.TZ1.25
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.3.hl.TZ1.25 |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Identify, Outline | Question number | 25 | Adapted from | N/A |
Methadone is a synthetic opiate administered as a racemic mixture to treat strong pain and morphine or heroin dependence.
Identify the chiral carbon atom using an asterisk, *.
[1]
[✔]
Some candidates had difficulty identifying the chiral carbon in a methadone structure, with quite a few varied answers. However, many managed to mark the correct carbon.
Enantiomers can be identified using a polarimeter. Outline how this instrument differentiates the enantiomers.
[2]
«plane-»polarized light passed through sample [✔]
analyser/second polarizer determines angle of rotation of plane of plane-polarized light
OR
each enantiomer rotates plane «of plane-polarized light» in opposite directions «by the same angle» [✔]
Very poorly answered. Few scored any marks at all when outlining how a polarimeter can be used to differentiate between enantiomers. Many referred to the light or the enantiomers themselves being rotated.
