HL Paper 3
A polarimeter can be used to determine the optical rotation of an optically active substance.
Describe what happens to plane-polarized light when it passes through a solution of an optically active compound.
A mixture of enantiomers shows optical rotation.
Suggest a conclusion you can draw from this data.
Technetium-99m is the most widely used medical radioisotope. It is usually made on-site in medical facilities from isotopes of molybdenum.
Deduce equations for the following nuclear reactions:
(i) Molybdenum-98 absorbs a neutron.
(ii) The isotope produced in (a) (i) decays into technetium-99m.
Molybdenum-99 has a half-life of 66 hours, while technetium-99m has a half-life of 6 hours. Outline why technetium-99m is made on-site.
Outline two reasons, other than its half-life, why technetium-99m is so useful in medical diagnosis.
Outline the nature of the radioactive waste that is generated by the use of technetium-99m in medical diagnosis.
Excess stomach acid leads to medical conditions that affect many people worldwide. These conditions can be treated with several types of medical drugs.
Omeprazole exists as a racemic mixture whereas esomeprazole is a single enantiomer. Outline how, starting from a non-chiral molecule, esomeprazole but not omeprazole, could be synthesized. Details of chemicals and conditions are not required.
Ibuprofen and paracetamol are mild analgesics. One of the IR spectra below belongs to ibuprofen and the other to paracetamol. The structures of both compounds are given in section 37 of the data booklet.
Both spectra show a peak at wavenumber 1700 cm–1. Identify the bond responsible for this peak.
Deduce which spectrum belongs to paracetamol, giving two reasons for your choice. Use section 26 of the data booklet.
Describe how mild analgesics function.
Ethanol can be detected by a variety of instruments.
Fuel cells use an electrochemical process to determine the concentration of ethanol.
Formulate the overall equation for this process.
Predict the chemical shifts and integration for each signal in the 1H NMR spectrum for ethanol using section 27 of the data booklet.
The use of performance-enhancing drugs presents a challenge in the world of competitive sports. New regulations have lowered the acceptable concentrations of certain drugs in athletes’ bodies.
Suggest what may have led to these changes in acceptable concentrations.
One class of performance-enhancing drugs is the anabolic steroids. Detection of these drugs in urine samples uses a combination of gas chromatography and mass spectrometry (GC/MS).
(i) Describe how gas chromatography enables the components of urine to be analysed.
(ii) The structures of two steroids, testosterone and nandrolone, are given below.
With reference to the molar masses of the two steroids, determine, with a reason, which can be identified from the mass spectrum below.
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.
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.
Some mild analgesics contain a solid mixture of acidic aspirin and a non-acidic organic chemical of similar polarity to asprin.
Discuss how acid-base properties and the process of solvent extraction can be used to separate aspirin from the mixture.
The pharmaceutical industry is one of the largest producers of waste solvents.
State a green solution to the problem of organic solvent waste.
Technetium-99m is the most commonly used isotope for diagnostic medicine.
State the type of radiation technetium-99m emits.
Discuss the properties that make a radioisotope suitable for diagnosis.
Describe the proper disposal of low-level radioactive waste in hospitals.
Technetium-99m has a half-life of hours. Calculate the amount of of technetium-99m remaining after hours.
Consider the structures of medicinal molecules in section 37 of the data booklet.
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.
Circle two chiral carbons in the section of the Taxol structure below.
Nuclear radiation is dangerous because of its ability to damage cells but it can also be used in nuclear medicine.
Iodine-131 is released in nuclear explosions but is used in scanners for thyroid cancer. The half-life of iodine-131 is 8.02 days.
Yttrium-90 is used in treating certain cancers.
Formulate a nuclear equation for the beta decay of yttrium-90.
Lutetium-177 is a common isotope used for internal radiation therapy.
Suggest why lutetium-177 is an ideal isotope for the treatment of certain cancers based on the type of radiation emitted.
Calculate the rate constant, , in day−1, for the decay of iodine-131 using section 1 of the data booklet.
Calculate the time, in days, for 90% of the sample to decay.
A breathalyser measures the blood alcohol content from a breath sample. Formulate half-equations for the reactions at the anode (negative electrode) and the cathode (positive electrode) in a fuel cell breathalyser.
Targeted Alpha Therapy (TAT) is a technique that involves using alpha-radiation to treat leukemia and other dispersed cancers.
Yttrium-90 and lutetium-177 are used in radiotherapy.
Explain why alpha-radiation is particularly suitable for this treatment.
Outline how the alpha-radiation in TAT is directed to cancer cells.
Identify the type of radiation emitted by these two radioisotopes.
State an equation for the one-step decay of yttrium-90.
The half-life of lutetium-177 is 6.75 days. Calculate the percentage remaining after 27 days.
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
Explain how IR spectroscopy can be used to distinguish aspirin from salicylic acid.
Some drugs are extracted from natural sources and others are synthetic.
Explain the role of the chiral auxiliary in the synthesis of Taxol.
Taxol was originally obtained from the bark of the Pacific yew tree.
Outline how Green Chemistry has improved the process of obtaining Taxol.
Radioisotopes can be used to treat a wide variety of diseases.
Phosphorous-32 undergoes beta decay. Formulate a balanced nuclear equation for this process.
The half-life of phosphorus-32 is 14.3 days. Calculate the mass, in g, of 32P remaining after 57.2 days if the initial sample contains 2.63 × 10−8 mol. Use table 1 of the data booklet and Mr = 31.97 g mol−1.
Explain the targeted alpha therapy (TAT) technique and why it is useful.
Lutetium-177 is used in radiotherapy. It emits beta radiation when it decays.
State a nuclear equation to show the decay of lutetium-177.
The half-life of lutetium-177 is 6.73 days. Determine the percentage of a sample of lutetium-177 remaining after 14.0 days.
Explain the low environmental impact of most medical nuclear waste.
A mixture of ethanal, ethanol and ethanoic acid is fractionally distilled.
Calculate the mole fraction of ethanal in the mixture.
The vapour pressure of pure ethanal at is .
Calculate the vapour pressure of ethanal above the liquid mixture at .
Describe how this mixture is separated by fractional distillation.
Ethanol slows down the reaction time of a driver leading to traffic accidents. Explain how the concentration of ethanol in a sample of breath can be determined using a fuel cell breathalyser.
Taxol is produced using a chiral auxiliary. Describe how the chiral auxiliary functions to produce the desired product.
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).
Suggest two absorbances, other than the absorbances due to the ring structure and C–H bonds, that would be present in the infrared (IR) spectrum of aspirin.
State two techniques, other than IR spectroscopy, which could be used to confirm the identity of aspirin.
Organic solvents are commonly used in the pharmaceutical industry.
Hexane and propanone have vapour pressures of 17 kPa and 24 kPa respectively at 20 °C.
Calculate the vapour pressure, in kPa, at 20 °C of a mixture containing 60% hexane and 40% propanone by mole fraction, using Raoult’s law and assuming the mixture is ideal.
Explain how hexane and propanone may be separated by fractional distillation.
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.
The resulting active metabolite of oseltamivir can be detected by mass spectrometry (MS) analysis.
Deduce the mass of the expected carboxylate ion.
Mr oseltamivir = 312
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.
Taxol is a chiral cancer drug which is synthesized using a chiral auxiliary.
The diagram shows part of a Taxol molecule in skeletal form.
Draw a circle around each chiral carbon.
Outline how chiral auxiliaries are used to synthesize the desired enantiomer.
Explain the process of solvent extraction by which Taxol is isolated.
Technetium-99m, a widely used radionuclide, has a half-life of 6.0 hours and undergoes gamma decay to technetium-99.
Most of the nuclear waste generated in a hospital is low-level waste (LLW).
Determine the percentage of technetium-99m remaining after 24.0 hours.
Technetium-99 decays further, emitting beta radiation. Formulate the equation for the decay of technetium-99.
Outline what is meant by low-level waste.
Outline the disposal of LLW.
Magnetic resonance imaging (MRI) is an application of NMR technology using radiowaves.
Suggest why MRI is much less dangerous than imaging techniques such as X-rays and radiotracers. Use section 3 of the data booklet.
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
The structure of penicillin is shown in section 37 of the data booklet.
State the internal bond angles in the b-lactam ring and the expected bond angles in sp2 and sp3 hybridised atoms.
Explain how the open β-lactam ring kills bacteria.
State how the structure of penicillin can be modified to combat the effect of resistance caused by over prescription.
Suggest why human cells are not affected by penicillin.
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.
Methadone is a synthetic opiate administered as a racemic mixture to treat strong pain and morphine or heroin dependence.
Identify the chiral carbon atom using an asterisk, *.
Enantiomers can be identified using a polarimeter. Outline how this instrument differentiates the enantiomers.
Taxol is a drug that was once obtained from yew trees and is now produced using chiral auxiliaries.
Examine the synthesis of taxol in terms of green chemistry criteria.
Outline the operation of a polarimeter used to distinguish between enantiomers.
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.
Taxol is an anticancer drug.
State the feature of Taxol that is a major challenge in its synthesis. Use section 37 of the data booklet.
Describe how the challenge in (a) was resolved by pharmaceutical companies.
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.
Opiates are strong analgesics.
Explain why diamorphine (heroin) crosses the blood–brain barrier more easily than morphine.
Outline the meaning of the bioavailability of a drug.
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.
Nuclear isotopes are used in the treatment of cancer.
Gamma radiation is also used in radiotherapy.
Alpha particles are more damaging to human cells than any other nuclear radiation and yet they are used in targeted alpha therapy (TAT).
Explain how TAT is relatively safe to use in the treatment of dispersed cancers.
Technetium-99m () has a half-life of 6.0 hours. Calculate the percentage of remaining in a sample of the radioisotope after two days.
Suggest why the percentage of technetium-99m remaining in the human body two days after injection will be lower than that calculated in (b)(i).
Many drugs, including aspirin, penicillin, codeine and taxol, have been modified from compounds that occur naturally.
Many drugs are chiral. Explain how a polarimeter can be used to determine the relative proportion of two enantiomers.
Mild heartburn is treated with antacids such as calcium carbonate.
Formulate an equation for the neutralization of stomach acid with calcium carbonate, CaCO3 (s).
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:
Medicines and drugs are tested for effectiveness and safety.
Distinguish between therapeutic window and therapeutic index in humans.
Therapeutic window:
Therapeutic index:
Explain why diamorphine (heroin) is more potent than morphine using section 37 of the data booklet.
A number of drugs have been developed to treat excess acidity in the stomach.
Outline how ranitidine (Zantac) functions to reduce stomach acidity.
Technetium-99m, Tc-99m, is a gamma-ray emitter commonly used as a medical tracer.
Its half-life is 6.0 hours.
Evaluate the suitability of technetium-99m for this use.
Calculate the percentage of technetium-99m remaining after 10.0 hours. Use section 1 of the data booklet.
Codeine, morphine and diamorphine (heroin) are derived from opium.
Explain why diamorphine has greater potency than morphine.
Experimental research on both animals and humans contributes to the development of pharmaceuticals.
State the meaning of the term therapeutic index in human studies.
The presence of alcohol in the breath can be detected using a breathalyzer.
Describe how a fuel cell breathalyser works.
Alcohol levels in the breath can also be determined using IR spectroscopy.
Suggest, giving a reason, which bond’s absorbance is most useful for detecting ethanol in breath.
Bond:
Reason:
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.
Outline the impact of antibiotic waste on the environment.
Suggest a concern about the disposal of solvents from drug manufacturing.
Discuss two difficulties, apart from socio-economic factors, associated with finding a cure for AIDS.
Aspirin can be obtained from salicylic acid.
Additional information can be obtained from the 1H NMR spectrum of aspirin.
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 diff erentiates salicylic acid from aspirin. Use section 26 of the data booklet.
Name:
Absorption band:
Deduce the protons responsible for signals X and Y by marking them on the structure of aspirin in (a). Use section 27 of the data booklet.
Identify the splitting pattern of signals X and Y.
X:
Y:
Steroids are lipids with a steroidal backbone. The structure of cholesterol is shown in section 34 of the data booklet.
Infrared (IR) spectroscopy is used to identify functional groups in organic compounds.
Deduce the wavenumber, in cm−1, of an absorption peak found in the IR spectrum of testosterone but not in that of cholesterol.
Describe a technique for the detection of steroids in blood and urine.
Explain how redox chemistry is used to measure the ethanol concentration in a breathalyser.
Scientists have developed various analytical techniques.
State an analytical technique used to separate anabolic steroids from other compounds in an athlete’s urine or blood.
Ethanol in breath can be detected by a redox reaction. Outline this method of detection. An equation is not required.
Viruses and bacteria both cause diseases and are frequently confused.
Outline two different ways in which antiviral medications work.
Nuclear medicine uses small amounts of radioisotopes to diagnose and treat some diseases.
State two common side effects of radiotherapy.
Explain why technetium-99m is the most common radioisotope used in nuclear medicine.
25.0 μg of iodine-131, with a half-life of 8.00 days, was left to decay.
Calculate the mass of iodine-131, in μg, remaining after 32.0 days. Use section 1 of the data booklet.
Radiotherapy is one type of treatment for cancer.
Describe how ionizing radiation destroys cancer cells.
Outline how Targeted Alpha Therapy (TAT) is used for treating cancers that have spread throughout the body.