February 2016 archive

HL only D9: drug detection and analysis

Nature of Science

Advances in technology (IR, NMR and MS) which enable very small amounts of substances to be analysed comprehensively have assisted in drug detection, identification, isolation and purification.

International-mindedness

Cheating by taking illegal or banned drugs in sport is an international problem.

A very basic overview of drug testing (for forensics) on this site.

After studying this topic students should be able to:

Understand:

  • Infrared spectroscopy, mass spectroscopy and proton NMR can all be used to analyse and identify organic structures. (Revise topic 11/21!) and see Videos here on IR, and H NMR and mass spectroscopy)
  • The presence of alcohol in a breath sample can be detected either by using a  redox reaction or by a breathalyser that uses a fuel cell.

Apply their knowledge to:

  • Determine an organic structure by interpreting a variety of analytical spectra (IR, mass spectroscopy and 1H NMR).
  • Describe the process of extraction and purification of an organic product. This should cover fractional distillation, Raoult’s law, and the properties on which extractions are based.
  • Explain the relationship between organic structure and solubility.
  • Describe how chromatography and mass spectroscopy can be used to detect the presence of steroids in sport .
  • Explain how alcohol can be detected by using a breathalyzer. (some basics of this process are here)

Clarification notes

Students should be able to identify common organic functional groups in a given compound by recognition of common drug structures and from Sections 26, 27 and 28 of the data booklet which give data on IR, 1H NMR and mass spectral fragments respectively.

A common steroid structure is given in Section 34 of the data booklet.

HL only: D8 – Nuclear Medicine

Nature of science

The benefits of the technique(s) being considered need to be balanced against the risks associated with the exposure to radiation.

 

What is nuclear stability and an example of a nuclear equation, in a video tutorial from Khan.  (Types of decay are the next video in the series, which you should watch if you are not in Physics, or if you are in Physics and didn’t pay attention in that part of the course).

How to write nuclear equations with the Khan Academy.

What is Technetium-99, the most widely used radioisotope in medicine? (see also Wikipedia on technetium-99m)

What is an MRI and how does it work? (Read the section on how it works in particular)

What is radiotherapy? How can it be used internally or externally? What are some common side effects?

See videos by Richard Thornley on Targeted alpha therapy (TAT) and Boron neutron capture therapy (BNCT).

Notes from IB:

The discussion of common side effects should include loss of hair, nausea, fatigue and sterility. The discussion should also include the damage to DNA and growing or regenerating tissue.

Students should know that the isotopes used in nuclear medicine include: Tc-99m, Lu-177, Y-90, I-131 and Pb-212.

Note taking sheet here. (Handed out in class Friday March 4)

Learning outcomes

After studying this topic students should be able to:

Understand

  • Many different types of emissions (e.g. alpha, beta, gamma, proton, neutron and positron) are used for medical investigations and treatment.
  • MRI (magnetic resonance imaging) is an application of NMR technology.
  • Radiotherapy can be used internally and/or externally.
  • TAT (targeted alpha therapy) and BNCT (boron neutron capture therapy) are two different methods used in the treatment of cancer.

Apply their knowledge to:

  • Discuss the common side effects of radiotherapy.
  • Explain (based on its half-life, emission type and chemistry) why technetium-99m is the most common radioisotope used in nuclear medicine.
  • Explain (based on the type of radiation emitted) why lutetium-177 and yttrium-90 are common isotopes used for radiotherapy .
  • Balance nuclear equations that involve alpha and beta particles.
  • Use the nuclear half-life equation to calculate both the percentage and the amount of radioactive material decayed and remaining after a certain period of time .
  • Explain TAT and how it can be used to treat diseases that have spread throughout the body.

International-mindedness

Culture, cost, availability and beliefs are some of the factors that can influence the use of nuclear technology in medicine and explain why its use is not consistent throughout the world.

Sample questions are in your textbook, and also handed out in class (e-version here. ) Make up three more, and trade with someone in the class.

HL only D7 – Taxol

Nature of Science

The demand for certain drugs is greater than the supply of natural substances required to synthesize them. However, due to advances in technology, many natural substances can now be produced in laboratories in large enough amounts to meet the demand.

International-mindedness

The availability and distribution of certain medicines and drugs around the world is unequal.

After studying this topic students should be able to:

Understand:

  • Taxol is a medicament that is commonly used to treat several different forms of cancer. (How Taxol works as an anti-cancer agent)
  • Taxol occurs naturally in certain types of yew tree but it is now commonly produced synthetically. (See article here about early synthesis results) (Video on Youtube about obtaining taxol from more than one type of Yew Tree)
  • Chiral auxiliaries are optically active substances that are incorporated temporarily into organic syntheses so that they can be carried out asymmetrically to selectively produce a single enantiomer. (Here is Richard Thornley, explaining chiral auxiliaries)

Apply their knowledge to:

  • Explain how paclitaxel (Taxol is the trademark name) is obtained and used as a chemotherapeutic agent.
  • Describe the use of chiral auxiliaries to form the desired enantiomeric product. (HL Article here from Science Journal on some specific ligands that are used for producing single enantiomers)

trans-2-phenylcyclohexan-1-ol – a chiral auxiliary used in the synthesis of taxol (Neuss, G, InThinking IB Chemistry, 2016).

  • Explain how a polarimeter can be used to identify enantiomers. (How does a polarimetre work again? remember in Topic 20?)

The structure of Taxol (paclitaxel) is given in Section 37 of the data booklet.

D 6 Green Chemistry

Please read section D6 in your textbook first, and then look at the following resources.

What is green chemistry? A video here from a scientist at Nottingham University.

Dealing with radioactive waste discussed in a video here.

How are drug companies managing solvents and reducing waste? Some ideas here.

A good article on green chemistry and solvent use in industry. (Poliakoff, Martyn, and Pete Licence. “Sustainable Technology: Green Chemistry.” Nature 450.7171 (2007): 810. Science Reference Center. Web. 10 Feb. 2016.) 

“Green chemistry encourages the reduction and prevention of pollution at source. It does this by trying to minimise the use and formation of substances harmful to the environment. Explain the concept of atom economy and stress its importance to green chemistry.

The different ways of synthesising oseltamivir (Tamiflu) are …(Very)… complex for IB students, so stress that each new way tries to provide a more sustainable route. The normal precursor is shikimic acid which can be obtained in low yield (2-7%) from a plant (the Chinese star anise plant). This is inefficient and environmentally unfriendly and cannot produce enough for industrial production. Synthesis of shikimic acid in the laboratory is a multi-step process with a very low atom economy. It can now be obtained in a much greener way through bioengineering using bacteria.” (G. Neuss, InThinking IB Chemistry, 2015)

International-mindedness

Pharmaceutical companies are multi-national companies. How do they determine how to spend their funds on research to develop new medications? For example, do they have a responsibility to research medications for rare diseases, even though it is unlikely to provide them with significant financial profit?
The production of a drug typically involves a number of different organic reactions. Consider the ethics governing the synthesis of new drugs. Are the standards and practices relating to the design and manufacture of pharmaceutical products the same worldwide, or do they vary by country and region?

After studying this topic students should be able to:

Understand:

  • High-level waste (HLW) is radioactive waste that emits large amounts of ionizing radiation for a long period of time.
  • Low-level waste (LLW) is radioactive waste that emits small amounts of ionizing radiation for a short period of time.
  • Resistance to antibiotics occurs when micro-organisms become resistant to antibacterials.

Apply their knowledge to:

  • Describe the environmental impact of the disposal of radioactive medical waste.
  • Discuss the environmental issues related to left-over solvents.
  • Explain the dangers associated with antibiotic waste, from the improper disposal of drugs and animal waste, and the development of antibiotic resistance.
  • Discuss the basics of green chemistry (sustainable chemistry) processes.
  • Explain how green chemistry was used to develop the precursor for oseltamivir (Tamiflu).