SL Paper 3
Medicines have a variety of different effects on the body and act at the molecular level.
Morphine and codeine are strong analgesics. Their structures are given in section 37 of the data booklet.
Dose response curves are determined for each drug.
Outline the significance of range “a”.
Suggest the type of reaction used to convert morphine to codeine.
State and explain the action of opiates as painkillers.
Solubility plays an important role in the bioavailability of drugs in the body.
Suggest why aspirin is slightly soluble in water. Refer to section 37 of the data booklet.
Formulate an equation for the conversion of aspirin to a more water soluble derivative.
A student prepares aspirin from salicylic acid in the laboratory, extracts it from the reaction mixture, ensures the sample is dry and determines its melting point.
Suggest why the melting point of the student’s sample is lower and not sharp compared to that of pure aspirin.
Organic molecules can be characterized using infrared (IR) spectroscopy.
Compare and contrast the infrared peaks above 1500 cm−1 in pure samples of aspirin and salicylic acid using section 26 of the data booklet.
The pharmaceutical industry is one of the largest producers of waste solvents.
State a green solution to the problem of organic solvent waste.
The structures of oseltamivir (Tamiflu) and zanamivir (Relenza) are given in section 37 of the data booklet.
Compare and contrast the structures of oseltamivir and zanamivir, stating the names of functional groups.
Deduce the wavenumber of one absorbance seen in the IR spectrum of only one of the compounds, using section 26 of the data booklet.
Suggest one ethical consideration faced by medical researchers when developing medications.
Oseltamivir (Tamiflu) and zanamivir (Relenza) are both used as antivirals to help prevent the spread of the flu virus, but are administered by different methods.
Zanamivir must be taken by inhalation, not orally. Deduce what this suggests about the bioavailability of zanamivir if taken orally.
Oseltamivir does not possess the carboxyl group needed for activity until it is chemically changed in the body. Deduce the name of the functional group in oseltamivir which changes into a carboxyl group in the body. Use section 37 of the data booklet.
The synthesis of oseltamivir is dependent on a supply of the precursor shikimic acid, which is available only in low yield from certain plants, notably Chinese star anise. State one alternative green chemistry source of shikimic acid.
Excess stomach acid leads to medical conditions that affect many people worldwide. These conditions can be treated with several types of medical drugs.
Ranitidine (Zantac) is a drug that inhibits stomach acid production. Outline why the development of this drug was based on a detailed knowledge of the structure of histamine, shown below.
Two other drugs, omeprazole (Prilosec) and esomeprazole (Nexium), directly prevent the release of acid into the stomach. Identify the site of action in the body.
A different approach to treating excess stomach acid is to neutralize it with antacids. Formulate an equation that shows the action of an antacid that can neutralize three moles of hydrogen ions, H+, per mole of antacid.
Consider the structures of medicinal molecules in section 37 of the data booklet.
Name two functional groups that both zanamivir and oseltamivir contain.
Explain how zanamivir works as a preventative agent against flu viruses.
Circle the side-chain in penicillin on the structure below.
Explain, with reference to the action of penicillin, why new penicillins with different side-chains need to be produced.
State and explain the relative solubility of codeine in water compared to morphine and diamorphine.
State the natural source from which codeine, morphine and diamorphine are obtained.
Penicillin is an antibiotic which contains a beta-lactam ring. Its general structure is shown below.
(i) Outline what is meant by the term “ring strain”.
(ii) On the diagram above, label with asterisk/s (*) the carbon atom/s that experience ring strain.
(i) Some antibiotic-resistant bacteria produce a beta-lactamase enzyme which destroys penicillin activity. Suggest how adding clavulanic acid to penicillin enables the antibiotic to retain its activity.
(ii) Populations of antibiotic-resistant bacteria have increased significantly over the last 60 years. Outline why antibiotics such as penicillin should not be prescribed to people suffering from a viral infection.
A number of drugs have been developed to treat excess acidity in the stomach.
Two drugs are ranitidine (Zantac) and omeprazole (Prilosec). Outline how they function to reduce stomach acidity.
0.500 g of solid anhydrous sodium carbonate, Na2CO3(s), is dissolved in 75.0 cm3 of 0.100 moldm−3 sodium hydrogen carbonate solution, NaHCO3(aq). Assume the volume does not change when the salt dissolves.
HCO3−(aq) CO32−(aq) + H+(aq) pKa = 10.35.
Calculate the pH of the buffer solution.
Aspirin is formed by reacting salicylic acid with ethanoic anhydride. The structure of aspirin is given in section 37 of the data booklet.
Deduce the structural formula of the by-product of this reaction.
Aspirin crystals are rinsed with water after recrystallization to remove impurities.
Suggest why cold water is used.
The solubility of aspirin is increased by converting it to an ionic form. Draw the structure of the ionic form of aspirin.
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing :
Minimum therapeutic dose
Estimated minimum lethal dose
The buffer formed by carbon dioxide, CO2(aq) and hydrogen carbonate ion, HCO3−(aq), plays an important role in maintaining the pH of blood.
Calculate the pH of the buffer from the following data and section 1 of the data booklet.
pKa(CO2) = 6.34
[HCO3−(aq)] = 1.40 × 10−2 moldm−3
[CO2(aq)] = 1.25 × 10−3 moldm−3
Explain the effect of a large amount of aspirin on the pH of blood.
Oseltamivir (Tamiflu) and zanamivir (Relenza) are antiviral drugs used to prevent flu.
State the names of two functional groups that both compounds contain, using section 37 of the data booklet.
Explain how oseltamivir and zanamivir can stop the spread of the flu virus in the body.
The production of many pharmaceutical drugs involves the use of solvents.
Suggest one problem associated with chlorinated organic solvents as chemical waste.
Suggest how the principles of green chemistry can be used to solve the environmental problems caused by organic solvents.
Aspirin is one of the most widely used drugs in the world.
Aspirin was synthesized from 2.65 g of salicylic acid (2-hydroxybenzoic acid) (Mr = 138.13) and 2.51 g of ethanoic anhydride (Mr = 102.10).
Calculate the amounts, in mol, of each reactant.
Calculate, in g, the theoretical yield of aspirin.
State two techniques which could be used to confirm the identity of aspirin.
State how aspirin can be converted to water-soluble aspirin.
Compare, giving a reason, the bioavailability of soluble aspirin with aspirin.
New drugs undergo thorough clinical trials before they are approved.
Outline the difference between the therapeutic index in animal studies and the therapeutic index in humans.
State the method of drug administration that gives the maximum bioavailability.
Some analgesics are derived from compounds found in plants.
Aspirin is a mild analgesic derived from salicylic acid found in willow bark.
Describe how mild analgesics function.
The strong analgesics morphine and codeine are opiates. Outline how codeine can be synthesized from morphine. The structures of morphine and codeine are in section 37 of the data booklet.
Explain why opiates are addictive.
Antiviral drugs are designed to take different approaches to fighting viruses.
Outline how oseltamivir (Tamiflu®) works.
Oseltamivir was commercially produced from shikimic acid, a precursor which is a metabolite in micro-organisms and plants.
Outline how green chemistry was used to develop the precursor for oseltamivir in order to overcome a shortage of the drug during the flu season.
Suggest why the administration of antibiotics to humans and animals can affect the environment.
Consider the following antacids:
Show that antacid X is more effective, per tablet, than antacid Y.
Radioisotopes are used to diagnose and treat various diseases. Explain the low environmental impact of most medical nuclear waste.
Excess acid in the stomach can cause discomfort and more serious health issues.
Explain how ranitidine (Zantac) reduces stomach acid production.
The pH is maintained in different fluids in the body by the use of buffers.
Calculate the pH of a buffer solution of 0.0200 mol dm–3 carbonic acid, H2CO3, and 0.400 mol dm–3 sodium hydrogen carbonate, NaHCO3. The pKa of carbonic acid is 6.35.
Molecules of antibiotics often contain a beta-lactam ring. Explain the importance of the betalactam ring in the action of penicillin, using section 37 of the data booklet.
Penicillins and aspirin are important medicines.
Describe how penicillin combats bacterial infections.
State how penicillins may be modified to increase their effectiveness.
State the type of reaction used to synthesize aspirin from salicylic acid.
Explain why aspirin is not stored in a hot, humid location.
The mild analgesic aspirin can be prepared in the laboratory from salicylic acid.
(CH3CO)2O + HOC6H4COOH → CH3CO2C6H4COOH + CH3COOH
Salicylic acid Aspirin
After the reaction is complete, the product is isolated, recrystallized, tested for purity and the experimental yield is measured. A student’s results in a single trial are as follows.
Literature melting point data: aspirin = 138–140 °C
Determine the percentage experimental yield of the product after recrystallization. The molar masses are as follows: M(salicylic acid) = 138.13 g mol−1, M(aspirin) = 180.17 g mol−1. (You do not need to process the uncertainties in the calculation.)
Suggest why isolation of the crude product involved the addition of ice-cold water.
Justify the conclusion that recrystallization increased the purity of the product, by reference to two differences between the melting point data of the crude and recrystallized products.
State why aspirin is described as a mild analgesic with reference to its site of action.
Many drugs, including aspirin, penicillin, codeine and taxol, have been modified from compounds that occur naturally.
Aspirin is often taken to reduce pain, swelling or fever. State one other use of aspirin.
State what is meant by the bioavailability of a drug.
Outline how the bioavailability of aspirin may be increased.
Compare and contrast the IR spectrum of aspirin with that of salicylic acid, using section 26 of the data booklet.
Describe how penicillin combats bacterial infections.
Outline two consequences of prescribing antibiotics such as penicillin unnecessarily.
State how penicillins may be modified to increase their effectiveness.
Morphine and codeine are strong analgesics. Outline how strong analgesics function.
Suggest one reason why codeine is more widely used than morphine as an analgesic.
Antiviral medications such as zanamivir (Relenza) are commonly available for consumer use.
Identify the names of two functional groups present in zanamivir using section 37 of the data booklet.
Distinguish between bacteria and viruses.
Opiates are strong analgesics.
Explain why diamorphine (heroin) crosses the blood–brain barrier more easily than morphine.
Describe the analgesic action of an opiate.
Outline the meaning of the bioavailability of a drug.
Antiviral drugs are a major research focus.
Oseltamivir (Tamiflu) and zanamivir (Relenza) are used against flu viruses. Explain how these drugs function.
Shikimic acid, the precursor for oseltamivir (Tamiflu), was originally extracted from star anise, and is now produced using genetically modified E. coli bacteria.
Suggest one difficulty associated with synthesizing oseltamivir (Tamiflu) from star anise.
Drug testing is necessary to determine safe and effective doses.
Distinguish between the lethal dose (LD50) and the toxic dose (TD50).
Excess stomach acid can be counteracted by a range of medications.
An antacid tablet contains 680 mg of calcium carbonate, CaCO3, and 80 mg of magnesium carbonate, MgCO3.
State the equation for the reaction of magnesium carbonate with hydrochloric acid.
Determine the amount, in mol, of hydrochloric acid neutralized by one antacid tablet.
Explain how omeprazole (Prilosec) reduces stomach acidity.
The structure of penicillin is shown in section 37 of the data booklet.
State the internal bond angles in the β-lactam ring and the expected bond angles for the same atoms in an open structure.
Explain how the open β-lactam ring kills bacteria.
Outline one effect of over-prescription of penicillin.
State how the structure of penicillin can be changed to combat this effect.
Suggest why human cells are not affected by penicillin.
Buffer systems control pH in the body.
Determine the pH of a buffer solution that is 0.0100 mol dm−3 sodium hydrogen carbonate and 0.0200 mol dm−3 sodium carbonate, using section 1 of the data booklet.
Ka (hydrogen carbonate ion) = 4.8 × 10−11
State the equation for the reaction of calcium carbonate, the active ingredient in some antacids, with stomach acid.
Suggest a technique for measuring the percentage mass of calcium carbonate in this type of antacid tablet.
Describe the proper disposal of low-level radioactive waste in hospitals.
Outline a green chemistry solution for problems generated by the use of organic solvents.
Mild heartburn is treated with antacids such as calcium carbonate.
Formulate an equation for the neutralization of stomach acid with calcium carbonate, CaCO3 (s).
Determine the volume of CO2 (g), in dm3, produced at STP, when 1.00 g of CaCO3 (s) reacts completely with stomach acid.
Mr CaCO3 = 100.09
Acid secretion can be regulated by other types of drugs such as omeprazole and ranitidine. Outline how each of these drugs acts to reduce excess stomach acid.
Omeprazole:
Ranitidine:
Drug synthesis often involves solvents.
Identify a common hazardous solvent and a Green solvent that could replace it.
The structures of morphine, diamorphine and codeine are given in section 37 of the data booklet.
Explain why diamorphine passes more readily than morphine through the blood-brain barrier.
Suggest a reagent used to prepare diamorphine from morphine.
Suggest one reason why codeine is available without prescription in some countries whilst morphine is administered under strict medical supervision.
Opium and its derivatives have been used for thousands of years as strong analgesics.
Explain how opiates act to provide pain relief.
Discuss how the difference in structure of two opiates, codeine and morphine, affect their ability to cross the blood–brain barrier. Use section 37 of the data booklet.
Aspirin can be obtained from salicylic acid.
Unreacted salicylic acid may be present as an impurity in aspirin and can be detected in the infrared (IR) spectrum.
Name the functional group and identify the absorption band that differentiates salicylic acid from aspirin. Use section 26 of the data booklet.
Name:
Absorption band:
Suggest two reasons why chlorinated solvents should neither be released into the atmosphere nor incinerated (burnt).
Excess acid in the stomach can cause breakdown of the stomach lining.
Outline how ranitidine (Zantac) inhibits stomach acid production.
Outline two advantages of taking ranitidine instead of an antacid which neutralizes excess acid.
Some antacids contain carbonates.
Determine the pH of a buffer solution which contains 0.160 mol dm−3 CO32− and 0.200 mol dm−3 HCO3−, using section 1 of the data booklet.
pKa (HCO3−) = 10.32
This question is about antiviral drugs.
Oseltamivir, used for the treatment of severe flu, is inactive until converted in the liver to its active carboxylate form.
Draw a circle around the functional group that can be converted to the carboxylate by hydrolysis.
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
Anti-HIV drugs, such as zidovudine, often become less effective over time.
Explain the development of resistant virus strains in the presence of antiviral drugs.
Medicines and drugs are tested for effectiveness and safety.
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
State one advantage of using morphine as an analgesic.
Explain why diamorphine (heroin) is more potent than morphine using section 37 of the data booklet.
Viruses and bacteria both cause diseases and are frequently confused.
State one way in which viruses differ from bacteria.
Outline two different ways in which antiviral medications work.
Staphylococcus aureus (S. aureus) infections have been successfully treated with penicillin and penicillin derivatives.
Identify the feature in penicillin responsible for its antibiotic activity.
The widespread use of penicillin and its derivatives has led to the appearance of resistant S. aureus strains.
Outline how these bacteria inactivate the antibiotics.
Outline how the structure of penicillin has been modified to overcome this resistance.
A student synthesized aspirin, acetylsalicylic acid, in a school laboratory.
0.300 g of crude aspirin was dissolved in ethanol and titrated with sodium hydroxide solution, NaOH (aq).
NaOH (aq) + C9H8O4 (in ethanol) → NaC9H7O4 (aq) + H2O (l)
Predict one absorption band present in an infrared (IR) spectrum of aspirin, using section 26 of the data booklet.
Determine the mass of aspirin which reacted with 16.25 cm3 of 0.100 mol dm−3 NaOH solution.
Determine the percentage purity of the synthesized aspirin.
Outline how aspirin can be chemically modified to increase its solubility in water.
State why aspirin should not be taken with alcohol.
Outline two factors which must be considered to assess the greenness of any chemical process.
Antiviral medications have recently been developed for some viral infections.
Outline one way in which antiviral drugs work.
Discuss two difficulties associated with solving the AIDS problem.
Body fluids have different pH values.
Identify the compound responsible for the acidity of gastric juice, and state whether it is a strong or weak acid.
An antacid contains calcium carbonate and magnesium carbonate.
Write the equation for the reaction of magnesium carbonate with excess stomach acid.
Outline how ranitidine reduces stomach acidity.
Calculate the pH of a buffer solution which contains 0.20 mol dm−3 ethanoic acid and 0.50 mol dm−3 sodium ethanoate. Use section 1 of the data booklet.
pKa (ethanoic acid) = 4.76
Infectious diseases can be caused by bacteria or viruses.
State one difference between bacteria and viruses.
Discuss two difficulties, apart from socio-economic factors, associated with finding a cure for AIDS.
The discovery of penicillins contributed to the development of antibiotics.
Explain how the beta-lactam ring is responsible for the antibiotic properties of penicillin. Refer to section 37 of the data booklet.
Codeine, morphine and diamorphine (heroin) are derived from opium.
State the names of two functional groups present in all three molecules, using section 37 of the data booklet.
Explain why diamorphine has greater potency than morphine.
The structure of aspirin is shown in section 37 of the data booklet.
Suggest one reactant used to prepare aspirin from salicylic acid.
Aspirin, C6H4(OCOCH3)COOH, is only slightly soluble in water.
Outline, including an equation, how aspirin can be made more water-soluble. Use section 37 in the data booklet.
Disposal of chemical waste is a growing problem in industry.
Outline the impact of antibiotic waste on the environment.
Suggest a concern about the disposal of solvents from drug manufacturing.
Excess acid in the stomach is often treated with calcium carbonate.
Formulate a chemical equation for the neutralization of stomach acid with calcium carbonate.
Calculate the amount, in mol, of stomach acid neutralized by an antacid tablet containing 0.750 g calcium carbonate.
Explain how omeprazole (Prilosec) regulates pH in the stomach.
Methadone, a synthetic opioid, binds to opioid receptors in the brain.
Compare and contrast the functional groups present in methadone and diamorphine (heroin), giving their names. Use section 37 of the data booklet.
Methadone is sometimes used to help reduce withdrawal symptoms in the treatment of heroin addiction. Outline one withdrawal symptom that an addict may experience.
Morphine and diamorphine (heroin) are both opioids.
Explain why diamorphine is more potent than morphine using section 37 of the data booklet.
Most of the nuclear waste generated in a hospital is low-level waste (LLW).
Outline what is meant by low-level waste.
Outline the disposal of LLW.