28 FALK— DEVELOPMENT OF THE [April 24. 



facts must be mentioned. A single bond between two atoms gives 

 no information as to the stability of the union between these atoms. 

 A double bond between two atoms cannot give any more information 

 with regard to the stability of the linking. Qualitatively it has been 

 found that the rate of reaction for compounds containing double 

 bonds is greater in some ways than the rate for compounds contain- 

 ing single bonds, and that with certain reagents decomposition at the 

 double bond occurs more rapidly than at other parts of the mole- 

 cule, but this is manifestly different from a discussion of true 

 stabilities of compounds. Reaction velocities bear no simple rela- 

 tion to stabilities of substances and "reactivity" as used in organic 

 chemistry very often refers only to these reaction velocities. The 

 double bond in the ordinary language signifies two units of valences 

 just as the single bond denotes one unit of valence, and in this sense, 

 the only permissible one, the representation of a double bond by 

 two lines is a correct picture of the linking when one line is used for 

 tlie single bond. 



When two atoms of elements which differ very markedly in elec- 

 trochemical properties are combined by a double bond, one of these 

 atoms may be considered to be electropositive and the other electro- 

 negative. In valence terms, an atom of one of these elements has given 

 up two negative electrons to the atom of the other to form the double 

 bond, the former becoming positive, the latter negative. These 

 cases are as simple as those in which only single bonds are involved. 

 Two units of valence are used in each linking with the result that 

 the valence of one of the atoms is 4~ 2 and of the other — -2 due to 

 the double bond. 



If two atoms of elements which do not differ much in electro- 

 chemical properties are combined by a double bond, the possible 

 relations from the electronic point of view are somewhat more com- 

 plex. On the other hand, explanations of reactions and classifica- 

 tions of isomers ahe afforded which are not possible with the view 

 of the double bond in which electrons are not considered. 



For the present purpose, it will be sufficient to outline some of 

 the relations. The substances to be considered include mainly the 

 compounds of carbon with double bonds between two carbon atoms 



