440 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



Kekulfs 

 graphic 

 formulae. 



Derivatives of 

 Marsh Gas, 



Marsh gas 

 Methyl chloride . 

 Carbonyl chloride 

 Carbonic anhydride 



Prussic acid . 



Derivatives of 

 Ethane. 



Ethyl chloride 

 Ethyl alcohol 

 Acetic acid . 

 Acetamide 



H H 



CH 3 -CH 2 -C1 H-C-C-C1 



H A 



TT TT 



CH 3 -CH 2 -OH K-C-C-OH 



CH 3 -CO-OH 



-ll 



OH 



CH 3 -CO-NH 2 H-C-C-NH, 



modern structural formulae, in which dots are used to show 

 the linkages between the radicals, and modern graphic 

 formulae, in which the linkages are shown in detail by a 

 series of straight lines. 



Kekule's formula for benzene (1865). The subsequent 

 history of organic chemistry has consisted largely of a 

 search for, and demonstration of structural formulae for 

 compounds of greater and greater complexity. At first 

 these compounds showed only " open-chains " of carbon 

 atoms, but Kekule himself in 1865 (Bull. Soc. C/iim., 1865, 



alternative formula. It will be seen that Kekule regarded sulphur as 

 bivalent in all its compound and nitrogen as tervalent ; modern formulae 

 often show sulphur as quadrivalent or sexavalent and nitrogen as 

 quinquevalent. 



