1.11 CHAPTER 1. ORGANICMOLECULES
Chapter 1 — Summary
See the summary presentation ( Presentation: VPmtm atwww.everythingscience.co.za)- Organic chemistry is the branch of chemistry that deals with organic molecules.
An organic molecule is one that contains carbon. - All living organisms contain carbon. Plantsuse sunlight to convert carbon diox-
ide in the air into organic compounds throughthe process of photosynthesis.
Animals and other organisms then feed on plants to obtain their ownorganic
compounds. Fossil fuels are another important source of carbon. - It is the unique properties ofthe carbon atom that give organic compounds
certain properties. - The carbon atom has four valence electrons, so it can bond with many other
atoms, often resulting in long chain structures. It also forms mostly covalent
bonds with the atoms that it bonds to, meaning that most organic molecules are
non-polar. - An organic compoundcan be represented in different ways, using its molecular
formula, structural formula or condensed structural formula. - If two compounds are isomers, it means that they have the same molecular for-
mulae but different structural formulae. - A functional group is a particular group ofatoms within a molecule, which give
it certain reaction characteristics. Organic compounds can be grouped according
to their functional group. - The hydrocarbons are organic compounds that contain only carbon and hydro-
gen. They can be further divided into the alkanes, alkenes and alkynes, based on
the type of bonds between the carbon atoms. - The alkanes have only single bonds between their carbon atoms and are unreac-
tive. - The alkenes have at least one double bond between two of their carbon atoms.
They are more reactivethan the alkanes. - The alkynes have at least one triple bond between two of their carbon atoms.
They are the most reactive of the three groups. - A hydrocarbon is said to be saturated if it contains the maximum possible number
of hydrogen atoms for that molecule. The alkanes are all saturated compounds. - A hydrocarbon is unsaturated if it does not containthe maximum numberof
hydrogen atoms for that molecule. The alkenes and alkynes are examples of
unsaturated molecules. If a double or triple bond is broken, more hydrogen
atoms can be added to the molecule. - There are three types of reactions that occur inthe alkanes: substitution, elimi-
nation and oxidation reactions. - The alkenes undergo addition reactions because theyare unsaturated.
- Organic compounds are named according to their functional group and its po-
sition in the molecule,the number of carbonatoms in the moleculeand the
position of any double and triple bonds. The IUPAC rules for nomenclature are
used in the naming of organic molecules.