The Open University since 2006
Alternatively you can skip the navigation by pressing 'Enter'.
Thinking Allowed 2016: 'Queer' wars, Nigerian beauty pageantsMonday, 30th May 2016 00:15 - BBC Radio 4Laurie Taylor and guests looks at the international polarisation over sexual rights and beauty contests in a... Read more: Thinking Allowed 2016: 'Queer' wars, Nigerian beauty pageants
The Educators: Series 2: Character LessonsMonday, 30th May 2016 23:30 - BBC Radio 4
Life - with David Attenborough: Creatures of the DeepTuesday, 31st May 2016 09:00 - Eden
Life - with David Attenborough: PlantsTuesday, 31st May 2016 10:00 - Eden
Old School With The Hairy Bikers: EPISODE 3Available until Sunday, 26th June 2016 20:00With only four weeks left at the Oxford Academy, we look to see how the old and young have learned from each other. Read more: Old School With The Hairy Bikers: EPISODE 3
Thinking Allowed 2016: 'Queer' wars, Nigerian beauty pageantsAvailable for over a year
All in the Mind - Summer 2016: Exams and the mental health of children, a community approach to suicide preventionAvailable for over a year
Thinking Allowed 2016: Glasgow gangs - Russian gangsAvailable for over a year
Life - with David AttenboroughDavid Attenborough explores the vibrant mix of life found on our plant - where it comes from, and... Read more: Life - with David Attenborough
Take the photographic memory testCan you capture scenes just by looking at them? Find out with our photographic memory test. Launch now: Take the photographic memory test
Una lengua en movimientoThis free course will develop your knowledge and understanding of the societies and cultures of... Try: Una lengua en movimiento now
Forensic psychologyIn this free course, Forensic psychology, you will discover how psychology can help obtain... Try: Forensic psychology now
What causes pain and how do we stop it? This free course, Pain and Aspirin, looks at how the human body responds to the release of certain chemicals and as a result feels pain. Pain can be reduced by inhibiting the formation of such chemicals and you will learn how the molecular structure of aspirin has been formulated to help in this process.
After studying this course, you should be able to:
- demonstrate general knowledge and understanding of some of the basic facts, concepts and principles relating to the development of medicines
- demonstrate knowledge and understanding of the science behind the development of some drugs to achieve particular tasks
- demonstrate knowledge and understanding of how chemical bonding determines the properties of compounds and provides an explanation for the mode of action of drugs
- apply this knowledge and understanding to address familiar and unfamiliar situations
- express unit concepts in an objective and factually correct way.
- Learning outcomes
- 1 Ouch – that hurts!
- 1.1 Why does it hurt?
- 1.2 How does it hurt?
- 1.3 The aspirin story
- 1.4 The molecules involved
- 1.5 Some chemistry involving esters
- 1.6 How does aspirin relieve pain?
- 1.7 Enzymes
- 1.8 Enter aspirin!
- Keep on learning
Study this free course
Enrol to access the full course, get recognition for the skills you learn, track your progress and on completion gain a statement of participation to demonstrate your learning to others. Make your learning visible!
Compare the structure of aspirin, 2.8, with that of salicylic acid, 2.7. What similarities and differences can you see?
The structures look quite similar. They both have a benzene ring carrying two groups, on adjacent carbon atoms. In both of them one of the groups is a carboxylic acid group. But, salicylic acid carries a phenol group whilst aspirin does not.
Can you identify the group that is carried by aspirin in the corresponding place to the phenol group in the molecule of salicylic acid? Have a look at options in Table 1.
You should have concluded that this is an ester group. If you did not identify this group correctly, try making a model. Remember there is free rotation about the single bonds and this should enable you to make it look like the ester group in Table 1.
You are going to study an important reaction between functional groups on molecules in this section. If you are new to chemistry you may not have seen chemical equations before, so before moving on work through Box 1 which provides you with a brief introduction to this topic.
Box 1 An introduction to chemical equations
When chemists want to refer to a chemical reaction in which bonds are broken and new bonds are formed to produce new molecules (the products) from other molecules (the reactants), they often do so by means of a chemical equation. The reactants are shown on the left and the products are on the right,
reactants = products
As atoms cannot be created or destroyed in chemical reactions, the total number of atoms of each element involved must be the same on each side of the equation, if the equation is to ‘balance’ correctly. The two sides are then linked by an equals (=) sign and the reaction is referred to as a ‘balanced reaction’.
For example, methane – the first molecule you made a model of and a fossil fuel gas – burns in the oxygen of the air to form carbon dioxide (CO2) and water (H2O). The reaction can be represented by the equation:
CH4 + 2O2 = CO2 + 2H2O
Count the atoms of each element on the left of the reaction and compare with the numbers on the right. They should be the same! Remember 2O2 means 2 × 2 = 4 atoms of oxygen (O).
Note the need for two molecules of oxygen and two molecules of water to balance the equation. The information that this equation contains is that one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
Sometimes the numbers of the molecules are unimportant and we just want to focus on the formulae of the reactants and products, not how much of each is involved. Chemists often show this type of relationship with a reaction having an arrow (→) instead of an equals sign. The following reaction is in this style:
CH4 + O2 H2O
Copyright & revisions
Originally published: Thursday, 24th March 2016
Last updated on: Thursday, 24th March 2016
- Creative-Commons: The Open University is proud to release this free course under a Creative Commons licence. However, any third-party materials featured within it are used with permission and are not ours to give away. These materials are not subject to the Creative Commons licence. See terms and conditions. Full details can be found in the Acknowledgements and our FAQs section.
- This site has Copy Reuse Tracking enabled - see our FAQs for more information.
If you enjoyed this, why not follow a feed to find out when we have new things like it? Choose an RSS feed from the list below. (Don't know what to do with RSS feeds?)
Remember, you can also make your own, personal feed by combining tags from around OpenLearn.
- Latest OpenLearn pages
- Latest pages from OpenLearn - Biology
- Latest pages tagged - pain
- Latest pages tagged - Maths
- Latest pages tagged - enzymes
- Latest pages tagged - health
- Latest pages tagged - mu123 Learning Club
- Latest pages tagged - pre course work
- Latest pages tagged - Units
- Latest pages tagged - using maths
- Latest pages tagged - Powero
- Latest pages tagged - Power station
- Latest comments on this page
All our alternative formats are free for you to download, for more information about the different formats we offer please see our FAQs. The most frequently used are Word (for accessibility), PDF (for print) and ePub and Kindle to download to eReaders*.
- Word (1.9 MB)
- PDF (2.4 MB)
- ePub 3.0 (1.5 MB)
- ePub 2.0 (1.5 MB)
- Kindle (520 KB)
- RSS (173 KB)
- HTML (1.6 MB)
- SCORM (1.6 MB)
- OUXML Package (22 KB)
- OUXML File (72 KB)
- IMS Common cartridge
*Please note you will need an ePub and Mobi reader for these formats.