HYDROCARBONS II 



another reaction takes place by which the four hydrogen atoms 

 are removed by the chlorine atom by atom, and each time a 

 hydrogen atom is removed a chlorine atom takes its place. 

 (See Exp. II, 2, e.) The steps in this series of reactions are as 

 follows : 



4 CH4 +4 CI2 -> 4 CH3CI + 4 HCl 



Methane 



3 CH3CI + 3 CI2 ^ 3 CH2CI2 + 3 HCl 

 2 CH2CI2 + 2 CI2 -> 2 CHCI3 + 2 HCl 

 CHCI3 + Cl2-> CCI4 + HCl 

 or 4 CH4+ioCl2->(CH3Cl+CH2Cl2+CHCl3+CCl4) + ioHCl 



Methane 



Such products formed from the hydrocarbons or other com- 

 pounds by substituting for one or more of the hydrogen atoms 

 an equivalent number of atoms of other elements are known 

 as substitution products, and the phenomenon is called substitu- 

 tion. We shall find that numerous series of substitution prod- 

 ucts are known which have different groups acting as substitutes. 

 The most important ones are those in which one of the halogen 

 elements (CI, Br, I), the hydroxyl group (OH), the amino group 

 (NH2), the nitro group (NO2), the sulphuric acid group (SO2OH), 

 the cyanogen group (CN) become substituted for a hydrogen 

 atom of a hydrocarbon. Also one oxygen atom (O) may take 

 the place of two hydrogen atoms. 



Of the substitution products just described as obtained from 

 methane by the action of chlorine two are well-known sub- 

 stances, viz. CHCI3, chloroform, and CCI4, carbon tetrachloride. 

 Collectively they are known as the chlor-methanes and they are 

 distinguished by prefixes denoting the number of chlorine 

 atoms substituted. The condensed structural formulas and 

 also the full structural formulas together with the names are 



shown as follows : 



H 



CH3CI — Mono-chlor-methane, H - C - CI 



I 

 H 



