Basic Organic Nomenclature

Alkanes

Family name: suffix: -ane

Carbon atoms are capable of forming 4 bonds (due to the 4 electrons in its valence shell). In alkanes the carbon atom will form 4 single bonds (or s (sigma) bonds) to 4 different atoms. The alkanes are also referred to as saturated hydrocarbons (they contain no multiple bonds), or paraffins. The geometry of these saturated or sp3 hybridized carbon atoms is tetrahedral (bond angles of approximately 109o). The general formula for an alkane is CnH2n+2 where n is the number of carbon atoms present in the molecule.
 


There are several conventions for writing chemical formulas and structures. In general the chemical formula will indicate the total number of each type of atom in the compound, i.e. C5H10O2. This does not give an indication of the structure of the compound. However there are several methods of relaying structural information. The first is a structural formula, i.e. CH3CH2CH2CH2COOH where the atoms are written out in the order they are bonded together. Another common method of displaying structural information is line drawings. In this style of diagram straight lines connect carbon atoms. Thus, unless otherwise indicated, each end of a straight line segment is a carbon atom. Hydrogen atoms are present to fill the 4 possible bonds the carbon atom may form. It is common to leave out all of the hydrogen atoms, except those bonded to heteroatoms (N, O, S...). i.e.
 
 




The structural formula and names for the simple alkanes are shown in the following table.
 
Number of 
C atoms
Formula
Line Drawing
Alkane Name
3D Model
1
CH4
N/A
methane
2
C2H6
ethane
3
C3H8 or
CH3CH2CH3
propane
4
C4H10 or
CH3(CH2)2CH3
butane
5
C5H12 or
CH3(CH2)3CH3
pentane
6
C6H14 or
CH3(CH2)4CH3
hexane
7
C7H16 or
CH3(CH2)5CH3
heptane
8
C8H18 or
CH3(CH2)6CH3
octane
9
C9H20 or
CH3(CH2)7CH3
nonane
10
C10H22 or
CH3(CH2)8CH3
decane
NOTE: The Chime displays can be manipulated, see the following tutorial for using Chime.
 

Next Page: Branched Alkanes

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