HYDROCARBONS. 



A. SATURATED. 



The simplest organic compounds are the hydrocarbons, which con- 

 sist of carbon united with hydrogen. 



Carbon is a tetravalent element, but, unlike other elements, the 

 carbon atom can combine with itself many times, thus 2, 3, 4, 5, 6, 

 etc., carbon atoms can be combined together. 



_U_i_U_L 

 i i i . i i i 



The hydrocarbons are the compounds in which the remaining 

 valencies of the carbon atoms so joined together are satisfied by 

 hydrogen, as for example in 



H H H H H H 



H C-H H-C C H H C C C H 



H H H H H H 



Methane. Ethane. Propane. 



They form a homologous series of compounds in which the member 

 containing i carbon atom more than the preceding one also contains 

 2 hydrogen atoms more, i.e. the members differ from one another 

 by CH 2 . They possess the general formula C n H 2 + 2- 



If we continue the process of adding CH 2 to propane, two ways 

 are possible : it may be added to one of the end carbon atoms or to 

 the middle carbon atom. The two compounds 



H 



H-C H 

 H H H H H | H CH 3 



H C C C C H and H C C C H or CH, C CH 3 



I I I I III I 



HHHH HHH H 



Butane. Isobutane or trimethyl-methane. 



are thus obtainable. Continuing the process we obtain 



49 



