| Date | May 2009 | Marks available | 2 | Reference code | 09M.3.hl.TZ1.D1 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | D1 | Adapted from | N/A |
Question
Analgesics are used to relieve pain in the body. Aspirin and paracetamol (acetaminophen) are both mild analgesics.
The structures of the strong analgesics morphine and heroin (diamorphine) can be found in Table 20 of the Data Booklet.
Explain the increased potency of heroin (diamorphine) compared to morphine.
Markscheme
polar hydroxyl groups in morphine are replaced by less polar/non-polar ester groups;
so facilitate transport into the non-polar environment of the central nervous system / increases the solubility in lipids / OWTTE;
Examiners report
Very few were able to fully explain the increased potency of heroin – some referred to polarity but did not identify the groups, and some the other way round, a few correctly stated that heroin was more lipid soluble so could cross the blood brain barrier more easily.
