Explain how mild and strong analgesics prevent pain.

Mild analgesics:

Strong analgesics:

State a reason why it is dangerous to use aspirin while consuming alcohol.

Deduce from the structures the names of two functional groups present in all three analgesics.

Deduce the name of one functional group present in diamorphine (heroin) but not in morphine or codeine.

Mild analgesics:

intercept pain stimulus at source / inhibit release of substances/prostaglandins that cause pain/swelling/fever / OWTTE;

Strong analgesics:

(temporarily) bond to receptor sites in brain / prevent transmission of pain impulses in central nervous system/CNS / OWTTE;

Award [1 max] if states that mild analgesics act at source and strong analgesics act at brain/CNS.

increased risk of stomach bleeding;

Any two for [1]

amine

benzene ring

alkene

ether

Allow benzene or phenyl (group) but not arene.

ester;

Names of functional groups must be stated for both marks in part (d).

Do not apply ECF in (d) if formulas (for example, C=C) given instead of names.

The mode of action of mild and strong analgesics in part (a) was well known by most candidates; however, the terminology used was sometimes inaccurate and reflected confusion. For example, some candidates talked about intercepting pain receptors on site of injury for mild analgesics.

Part (c) was well answered by the majority of candidates (increased risk of stomach bleeding when alcohol is consumed with aspirin), and two-thirds of the candidates identified the functional groups correctly in part (d). A common mistake was using the term esther which was not clear whether it was meant to indicate ether or ester.

Part (c) was well answered by the majority of candidates (increased risk of stomach bleeding when alcohol is consumed with aspirin), and two-thirds of the candidates identified the functional groups correctly in part (d). A common mistake was using the term esther which was not clear whether it was meant to indicate ether or ester.

Part (c) was well answered by the majority of candidates (increased risk of stomach bleeding when alcohol is consumed with aspirin), and two-thirds of the candidates identified the functional groups correctly in part (d). A common mistake was using the term esther which was not clear whether it was meant to indicate ether or ester.