HYDROCARBONS I 5 



CH3-H, Methane 



CH3 — CH3, Ethane (Methyl methane) 



CH3 - CH2 - CH3, Propane (Methyl ethane) 



CH3 - CH2 - CH2 - CH3, Butane (Methyl propane) 



CH3 - CH2 - CH2 - CH2 - CH3, Pentane (Methyl butane) 

 CH3 - CH2 - CH2 - CH2 - CH2 - CH3, Hexane (Methyl pentane) 



CH3 — (CH2)58 — CH3, Hexacontane 



From each one of these hydrocarbons substitution products 

 may be formed containing various elements or groups, CI, 

 Br, I, (OH), (NH2), (CN), etc. 



ISOMERISM 



When we come to study the substitution products of pro- 

 pane we find a new phenomenon. When propane, C3H8, or 

 CH3— CH2 — CH3, is converted into monoiodo-propane or propyl 

 iodide, there are formed two compounds of identical composition 

 but of distinctly different properties. Such compounds of like 

 composition but different properties are known as isomeric 

 compounds and the phenomenon is known as isomerism. 

 Isomerism we shall find is a most striking and important phe- 

 nomenon of organic compounds. 



The explanation of the formation of two propyl iodides is 

 derived from our idea of the structure of propane. By examin- 

 ing the formula of propane, 



H H H 



CH3-CH2-CH3 or H-C-C-C-H Propane 



H H H 



we see that the six hydrogens in the two end carbon groups may 

 be considered to be in a different relation, in the compound, to 

 the two hydrogens united to the middle carbon. If then one 

 hydrogen of each of these two sets is substituted, one at one 

 time and the other at another time, by iodine, we can represent 

 the resulting compounds by the following structural formulas r 



