Chapter 23:Alkanes and Alkenes

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Organic chemistry

• Organic Chemistry is the study of organic compounds.

Organic compounds

• Organic compounds are compounds which contain the element 'carbon'.
• They might contain 'hydrogen'
• Organic compounds which contain carbon and hydrogen only are known as

• Saturated hydrocarbons- each carbon has single bonds and surrounded by four other atoms.(Alkanes)

• Unsaturated hydrocarbons- each carbon has double bonds. (Alkenes)

Homologous Series

A homologous series refers to a family of organic compounds with the same general formula and similar chemical properties.

• Similar chemical properties
• Same functional group (except alkanes homologous series)
• Represented by a General Formula
• Regularly increasing relative molecular masses from one member to the next member
• Can be prepared by similar methods
• Gradual change in physical properties from one member to the next member

Functional Group

A functional group is defined as an atom or a group of atoms that gives a molecule its characteristic properties

• Alkanes – There are only C-C and C-H covalent bonds in the molecules
• Alkenes – Contain the carbon-carbon double bond, C=C.
• Alcohols – Contain the hydroxyl group, -OH
• Carboxylic acids – Contain the carboxyl group, -COOH

Naming of Organic Compounds

The naming of organic compound is divided into three parts:

• Part 1: Length of the parent chain i.e. the number of carbon atoms in the longest continuous unbroken chain(prefix)
• Part 2: Functional Group found in main parent chain [Suffix]
• Part 3: Side group that are attached to the main parent chain [ Substituent]

Formulae

• Empirical  formula which is the simplest whole no. ratio of atoms of each element
• Molecular formula which is the total no. of atoms of each element in each molecule
• Structural formula which shows how atoms are arranged in the molecule
• Full Structural formula which shows all the bonds between atoms in a molecule.

Isomers

• Isomers: have the same molecular formula but different structural formula (arrangement of atoms).
• eg  Butane

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