Diamorphine (heroin) is a more effective painkiller than morphine. The structures of morphine and diamorphine are shown in Table 20 of the Data Booklet. Explain at the molecular level why diamorphine is absorbed into fatty tissue more rapidly than morphine.

diamorphine has (2) ester/acetyl/\({\text{COOC}}{{\text{H}}_3}\) groups instead of hydroxyl/OH groups;

diamorphine is less polar/non-polar;

Most candidates answered the question satisfactory, though some did not name the difference in polarity in (b).