Doc Brown's GCSE/IGCSE KS4 science-CHEMISTRY Revision Notes

Oil, useful products, environmental problems, introduction to organic chemistry

8. Introduction to Organic Chemistry - Why so many series of organic compounds?

You might have already come across several organic molecules e.g. methane an alkane, ethene an alkene, ethanol an alcohol, ethanoic acid a carboxylic acid and ethyl ethanoate an ester. This page gives you some idea why such a variety of different molecules can exist based on carbon atoms combined with those of hydrogen, oxygen and nitrogen etc. The different types of organic molecules are classified in what are called homologous series.

Index of KS4 Science GCSE/IGCSE Chemistry Oil & Organic Chemistry Pages: 1. Fossil Fuels : 2. Fractional distillation of crude oil & uses of fractions : 3. ALKANES - saturated hydrocarbons and combustion : 4. Pollution, carbon monoxide, nitrogen oxides, what makes a good fuel?, climate change-global warming : 5. Alkenes - unsaturated hydrocarbons : 6. Cracking - a problem of supply and demand, other products : 7. Polymers, plastics, uses and problems : 8. Introduction to Organic Chemistry - Why so many series of organic compounds? : 9. Alcohols - Ethanol - properties, reactions, biofuels : 10. Carboxylic acids and esters : 11. Addition polymers and condensation polymers : 12. Natural Molecules - carbohydrates - sugars - starch : 13. Amino acids, proteins, enzymes & chromatography : 14. Oils, fats, margarine and soaps : 15. Vitamins, drugs-analgesic medicines & food additives and aspects of cooking chemistry! : 16. Ozone, CFC's and free radicals : 17. Extra notes, ideas and links on Global Warming and Climate Change : Multiple Choice and Gap-Fill Quizzes: m/c QUIZ on Oil Products (GCSE/IGCSE easier-foundation-level) : m/c QUIZ on Oil Products (GCSE/IGCSE harder-higher-level) : IGCSE/GCSE m/c QUIZ on other Aspects of Organic Chemistry : and 3 Easy linked GCSE/IGCSE Oil Products word-fill worksheets

8. Why are there families of organic compounds? - variety !

We have already introduced two series of organic molecules, which illustrate the fact that organic chemistry is the chemistry of carbon based compounds,

namely alkanes like butane, and alkenes like ethene

but there are many more series of organic molecules, so why such variety?

Organic compounds [*] belong to different families, though all organic compounds are based on carbon C, hydrogen H, and other elements such as ...

oxygen O e.g. alcohols like ethanol CH₃CH₂OH, and ...

nitrogen N e.g. in H₂NCH₂COOH the simplest of the amino acids

Most food is chemically organic in nature, apart from some minerals, and many drugs and plastic materials are composed of organic molecules, consequently, organic compounds and organic chemistry is rather important to us!

The compounds in each family have a similar chemical structure and a similar chemical formula. Each family of organic compounds forms what is called a homologous series. Different families arise because carbon atoms readily join together in chains (catenation) and strongly bond with other atoms such as hydrogen, oxygen and nitrogen. The result is a huge variety of 'organic compounds' which can be classified into groups of similar compounds i.e. different homologous series.

The term organic compound comes from the fact that most of the original organic compounds studied by scientists-chemists came from plants or animals, i.e. of natural origin. These days most organic compounds are synthesised from raw materials, in particular the physical separation and chemical manipulation of the products of crude petroleum oil.

• A homologous series is a family of compounds which have a general formula* and have similar chemical properties because they have the same functional group of atoms (e.g. C=C alkene, C-OH alcohol or -COOH carboxylic acid).
• Members of a  homologous series have similar physical properties such as appearance, melting/boiling points, solubility etc. but show trends in them e.g. steady increase in melting/boiling point with increase in carbon number or molecular mass.
• The molecular formula represents a summary of all the atoms in the molecule e.g. butane is C₄H₁₀.
• The structural or displayed formula shows the full structure of the molecule with all the individual bonds and atoms shown (though there are different 'sub-styles' of varying detail)
  • e.g.   all represent ethane
• When a specific group of atoms in a molecule give it a particular set of characteristic reactions, that group of atoms is called the functional group of the molecule. Examples of functional groups include:
  • the double carbon-carbon bond >C=C< in alkenes,
    • eg and
  • the oxygen-hydrogen atom group of the C-OH structure in alcohols,
    • eg   and 
  • and the group of four atoms constituting the -COOH and -COOC- groups in carboxylic acids and esters
    • eg  and 
• NOTE: Inorganic compounds are all the other compounds not based on carbon, except for carbon monoxide CO, carbon dioxide CO₂ and carbonates, which are also considered to be inorganic.
  • Examples of inorganic compounds: water H₂O, ammonia NH₃, sodium chloride NaCl, calcium carbonate CaCO₃

Multiple Choice Quizzes and Worksheets

KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (easier-foundation-level)

KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (harder-higher-level)

KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry

and 3 linked easy Oil Products gap-fill quiz worksheets

ALSO gap-fill ('word-fill') exercises originally written for ...

... AQA GCSE Science Useful products from crude oil AND Oil, Hydrocarbons & Cracking etc.

... OCR 21st C GCSE Science Worksheet gap-fill C1.1c Air pollutants etc ...

... Edexcel 360 GCSE Science Crude Oil and its Fractional distillation etc ...

... each set are interlinked, so clicking on one of the above leads to a sequence of several quizzes

Advanced Level Organic Chemistry revision notes

Revise KS4 Science GCSE/IGCSE/O level Chemistry Revision-Information Study Notes for revising for AQA GCSE Science, Edexcel 360Science/IGCSE Chemistry & OCR 21stC Science, OCR Gateway Science WJEC/CBAC GCSE science-chemistry CCEA/CEA GCSE science-chemistry (and courses equal to US grades 8, 9, 10)

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