560 



CONSIDERATION OF CARBON COMPOUNDS. 



The molecular formula of the above three compounds is C 6 H 6 O 2 , 

 apparently indicating benzene in combination with two atoms of 

 oxygen or dioxybenzene ; actually they are dihydroxy benzene. 



Otfto-dihydroxy benzene, C 6 H 4 OHOH, or C 6 H 4 (OH) 2 1 : 2, is known 



1 3 



as pyro-catechin, wefa-dihydroxy benzene, C 6 H 4 OHOH, or C 6 H 4 (OH) 2 



1 4 



1:3, as resorcin, and >ara-dihydroxy benzene, C 6 H 4 OHOH, or 

 C 6 H 4 (OH) 2 1 : 4, as hydroquinone. 



Benzene derivatives. The analogy existing between methane- 

 and benzene-derivatives may be shown by comparing the composition 

 of a few derivatives : 



The following graphic formulas may serve to illustrate the consti= 

 tution of some aromatic compounds : 



OH 



J 



^ 



A 



Benzene, CH. 



C0 2 H 



r I 



H 



i 



H 



Phenol or carbolic acid, Benzoic acid, C 6 H 5 .CO9H. 

 C 6 H 5 .OH. 



