50 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



H 



H C H 

 HHHHH HH I H CH 3 



H C C C C C H H C C C C H or C 3 H B C CH, 



Pentane. Dimethyl-ethyl-methane. 



H 



H C H 

 H I H H 



H C C C C H H 



4 A 



H C H 



i 



Dimethyl-ethly-methane. Tetramethyl-methane. 



Two of these compounds are identical in structure, so that only 

 three compounds can be derived from butane and isobutane. 



Two or more compounds which have the same empirical composi- 

 tion (C 4 H 10 or C 5 H i2 ), but a different structure as represented by the 

 graphic formulas, are therefore possible. Such compounds are known 

 as isomers. 



The compounds with a straight chain of carbon atoms are 

 termed normal compounds. Those with a branched chain of carbon 

 atoms are regarded as derivatives of methane, the radicles CH 3 , C 2 H 6 , 

 C 3 H 7 , etc., being termed methyl, ethyl, propyl, etc., which shows 

 their origin from the parent hydrocarbon. 



In accordance with this theory an enormous number of hydro- 

 carbons are possible ; those containing from I up to 60 atoms of carbon 

 in their molecule are actually known. The theory was advanced and 

 developed to account for their large number. 



The saturated hydrocarbons are the basis of the nomenclature and 

 classification of all the carbon compounds. The carbon compounds 

 are classified according as to whether they contain I, ?, 3, or 4, etc., 

 carbon atoms in their molecule, i.e. whether they are derived from 

 methane, ethane, propane, butane, etc. 



The saturated hydrocarbons are thus distinguished by the suffix am ; 

 the prefix meth means I carbon atom ; eth means 2. carbon atoms ; 

 prop means 3 carbon atoms, and so on. 



The majority of the saturated hydrocarbons are natural substances. 

 The lower members of the series of the hydrocarbons (up to 4 carbon 

 atoms, which are gases) are formed by the dry distillation of diverse 

 organic substances and are contained in coal gas. Methane occurs in 



