Eicosane, isomers

Constitutional isomerism becomes more complex as the size of the hydrocarbon molecule is increased. For example, there are three constitutional isomers of pentane, C5H12. The number of constimtional isomers increases quite rapidly with an increasing number of carbon atoms. Thus, there are five constimtional isomers of hexane, CeH, nine isomers of heptane, C7H16, 75 isomers of decane, C10H22, and 366,319 isomers of eicosane, C20H42. You can begin to understand why it is possible to make so many different molecules based on carbon. 

They have a different structure, although they both have the same molecular formula. One is called normal butane, abbreviated to -butane the other may be called isobutane or 2-methylpropane - the latter name describes the structure of the compound, as you will see later. These compounds are isomers of one another. They are not the same compounds and have different melting points, boiling points and solubilities. Isomers are compounds which have the same moiecuiar formuia, but different moiecuiar structures. After butane, the longer the carbon chain of an alkane, the more structurai isomers are possible for a particular molecular formula. For example, there are 75 decanes (C10H22) and over three-hundred-thousand eicosanes (C20H42) ... 

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