| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.sl.TZ0.17 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 17 | Adapted from | N/A |
Question
Opiates have been used for thousands of years to alleviate pain. The structures of opiates are found in section 37 of the data booklet.
Diamorphine (heroin) can be synthesized from morphine. Identify the reagent necessary for this reaction and the by-product of this reaction.
The reaction can be monitored by infrared spectroscopy. Using section 26 of the data booklet, identify two IR absorbance ranges that would help distinguishing the two compounds.
Present in morphine but not in diamorphine:
Present in diamorphine but not in morphine:
Discuss how the differences in structure between morphine and diamorphine affect their absorption in the body.
Markscheme
Accept names or structural formulas for reagent and by-product.
Accept IUPAC or alternative names of compounds e.g. acetic acid.
Award M2 only if the by-product corresponds to the reagent.
Present in morphine but not in diamorphine:
«has OH and absorbance at» 3200–3600 «cm–1»
Present in diamorphine but not in morphine:
«has C=O and absorbance at» 1700–1750 «cm–1»
morphine has «two» hydroxyl «groups» AND diamorphine/heroin has «two»
ester/ethanoate/acetate «groups»
morphine is more polar than diamorphine/heroin
diamorphine/heroin crosses the blood-brain barrier «easily»
morphine is <more> soluble in blood «plasma»
OR
diamorphine/heroin is «more» soluble in lipids
Accept converse argument throughout. Accept “alcohol/hydroxy” for “hydroxyl” but not “hydroxide”.
Do not accept “diamorphine/heroin is non-polar” for M2.
