Fundamentals of organic chemistry
10.1 Fundamentals of organic chemistry (4.5 hours)
Pause for thought
‘Fundamentals of organic chemistry' is rather a strange name for this first sub-topic. There are no explanations given as to why organic chemistry is important or why more compounds of carbon are known than the sum of all the compounds of all the other elements present in the periodic table. There is also no explanation as to why the chemistry of carbon is called ‘organic’ chemistry. Essentially this sub-topic lists several classes of compounds and students are required to understand the difference between 'class' and 'functional group' and be able to relate properties such as boiling points to members of each class. The classes specified are alkanes, alkenes, alkynes, halogenoalkanes, alcohols, ethers, aldehydes, ketones, esters, carboxylic acids, amines, amides, nitriles and arenes. They are also expected to be able to deduce and/or recognise the names and structures for compounds containing up to six carbon atoms in these classes and to make 3-D models of these compounds. They should also understand the terms homologous series and structural isomers and know the difference between saturated and unsaturated and be able to discuss the evidence for the structure of benzene.
Naming organic compounds can cause some problems even when the compounds are relatively simple. Generally the IB follows the preferred IUPAC naming system. So that CH3CH(OH)CH3 is called propan-2-ol by the IB when referred to in the syllabus or in examination questions although 2-propanol or isopropyl alcohol are both perfectly acceptable alternative names and would be accepted by the IB in a student's answer to a question (although isopropyl alcohol would not be accepted if the questions asked specifically for the IUPAC name).
Students should be familiar with the various ways of representing organic molecules. These include full structural formulas showing the bonds between all the atoms and condensed structural formulas. They should also be able to use and interpret the various different ways of modelling molecules, including ball and stick and space-filling models. To exemplify this, the following are some of the different ways of representing propan-2-ol. Note that the last two are skeletal or part-skeletal structures and these should also be known by students for the IB. Because a line represents two carbon atoms in a skeletal structure students must show all the hydrogen atoms when they are giving the full structural formula of a compound.
Nature of Science
Organic chemistry contains many examples of serendipity in the discovery of compounds and their uses, e.g. penicillin, teflon and superglue.
Organic chemistry also provides many instances where ethical implications are important. For example, drugs, pesticides and additives can all have positive and negative effects on humans, other animal species and the environment.
Learning outcomesAfter studying this topic students should be able to: Understand
Apply their knowledge to:
| Clarification notesStudents should know that skeletal formulas can be used to represent organic molecules. Students should know the general formulas of alkanes, alkenes, alkynes, ketones, alcohols, aldehydes and carboxylic acids . For example, the general formula of saturated alcohols is CnH(2n+1)OH. Student should be able to distinguish between class names and functional group names. For example, for compounds containing the -OH group, alcohol is the class The following nomenclature should be covered: International-mindednessGlobal policies and economic development are often shaped by supply and demand. This is especially evident with the world's reserves of oil as relatively few countries have control over its extraction and supply. The performance of the fuel used in cars and aircraft is measured by its octane number or octane rating. Octane ratings can differ quite widely from country to country. This is further complicated by the fact that different countries use different ways to express the values. |
Teaching tipsAfter an initial lesson on why organic chemistry is so special I launch into this by looking at the alkanes. They can be used to exemplify an homologous series and also their IUPAC names follow a logical sequence once you reach C5. I get students to draw the Lewis structures and also make models as we go down the series. They can see that butane has two isomers and this can be used to begin to show the numbering system so that isobutane becomes 2-methylpropane. By giving the boiling points students can see that the rate of increase in boiling point decreases as each -CH2 is added as the percentage increase in mass becomes less each time. Alkanes are obviously not miscible with water as they are non-polar. By assuming an alkane is R-H students can see that R is an organic radical and the -H can be replaced by different functional groups such as -OH, -CHO, -Cl etc. Students should then begin to understand how to name compounds systematically and you can give them example of structures they have to name and compounds they have to draw from the name. Solubility is not specifically mentioned in this sub-topic but whether they are soluble in water or not depends on the polarity of the R group. -OH, -NH2 and -COOH can form hydrogen bonds with water molecules and -COR and -CHO are polar and so can form dipole-dipole interactions with water. By making their own models students can see that there must be free rotation around a carbon atom that has four other atoms bonded to it. This should help them work out the structural isomers of pentane and hexane and not be fooled by diagrams of normal hexane for example showing 90o angles, i.e.
are both structural representations of the same molecule. Note that the IB emphasises the difference between the class of compounds and functional group. In the past 'alcohol' was accepted as the functional group name for -OH. This is no longer the case. -OH is the hydroxyl functional group and compounds containing the -OH group are known as alcohols. You can use the data book to extend the examples for classes of compounds, functional groups and whether compounds are primary, secondary or tertiary (see Classes of compounds & functional groups under Novel uses for the IB data booklet). | Study guide
Page 79 - 83 QuestionsFor ten 'quiz' multiple choice questions with the answers explained see MC test: Fundamentals of organic chemistry. For short-answer questions which can be set as an assignment for a test, homework or given for self study together with model answers see Fundamentals of organic chemistry (1) questions and Fundamentals of organic chemistry (2) questions. Vocabulary listIUPAC
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Teaching slides
Teachers may wish to share these slides with students for learning or for reviewing key concepts.
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Other resources
1. There are many rather boring videos on YouTube on naming organic compounds. It is not really a topic to make an exciting video but Mark Rosengarten seems to have managed it with this video by setting it all to music. Some students might enjoy it.
2. A video by Richard Thornley showing how the different strengths of intermolecular forces of attraction affect volatility and solubility in water for several different classes of organic compounds.