Homologous Series: Alkanes

 

A FUNCTIONAL GROUP  is an atom or combination of atoms which gives an organic molecule its distinctive and characteristic chemistry. A homologous series is a group of molecules with the same general formula and the same functional group. They have similar physical and chemical properties (albeit with trends e.g. increasing boiling point with increasing carbon chain length).

Alkanes, also known as paraffins,  contain C and H only, linked  by single bonds (i.e., they are saturated)

Each carbon atom must have 4 bonds (covalent C-H or C-C), and each hydrogen atom must be joined to a carbon atom (H-C bonds).

The C-H bond in general is very unreactive and alkanes have a low solubility in water. The burn well, however. Generally, the longer the C-C chain the smokier the flame

This graph shows the m.p and b.p’s of the first 14 alkanes.

Make sure you can draw CH4 and C2H6

In general : Alkanes – CnHn+2


More about covalent bonding later.

Temperature in Celsius on the vertical axis. Carbon #1-14 shown
Temperature in Celsius on the vertical axis. Carbon #1-14 shown

 

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