CONSTITUTION OF CHEMICAL COMPOUNDS. XXV11 



compounds is exactly the same as that of the hydrocarbon 

 itself. 



Just as marsh gas may be considered as the mother- 

 substance of a whole group of carbon-compounds, so, by re- 

 placing its hydrogen-atoms by various groups, we obtain 

 compounds, each of which may, in turn, be looked upon 

 as the mother-substance of a subordinate group. It has 

 already been shown that the water-residue, hydroxyl, OH, 

 plays an important part in the structure of the two classes 

 of compounds known as acids and bases. If, for a hydro- 

 gen-atom of marsh gas, we substitute OH, we obtain a 



H 



compound H.Q.OH == CH 3 (OH). This possesses the pro- 

 EC 



perties of the bases in general, corresponding to the sim- 

 pler base K.O.H. We have in this case only CH 3 , instead 

 of the element K. Here, too, the hydrogen-atom, which is 

 in combination with oxygen, imparts to the compound its 

 characteristic properties, whereas the other hydrogen- 

 atoms present exhibit only those other general properties 

 which are met with in connection with the hydrogen-atoms 

 of other groups of carbon-compounds. One or all of these 

 latter can be replaced by other elements or groups, and 

 the compound still retains the properties originally im- 

 parted to it by the hydroxyl group. We can, for instance, 

 replace one of these atoms by CH 3 , thus obtaining a com- 



HH 

 pound, H-C-C-O.H = C 2 H 5 (OH). This in every way re- 



HH 



sembles the body from which it is derived. We can, 

 further, in this compound replace one or more hydrogen- 

 atoms by elements or groups, without disturbing the hy- 

 droxyl-group. Let us again employ the group CH 3 . We 

 find that two products are formed, dependent upon the 

 hydrogen-atoms replaced : 



HHH 



H '0 ' 



H -C- C-C-O.H, and 2. H-C C-O'H, 

 HjHH H H 



and, just as in the case of the hydrocarbon C 4 H 10 , the two 

 products differ from each other in properties as well as in 

 constitution. 



