424 



GIBBS. 



which is strongly borne out by the facts. Moreover, the aniline absorption 

 band is of great persistence, that is, it is visible over a wide range of dilu- 

 tions, and this persistence is a measure of the reactivity and the number 

 of molecules of the compound which are undergoing transformation at 

 any moment. 



Since there is a labile hydrogen atom in the aniline molecule there are 

 periods in the dynamic equilibrium when a group in the nascent condition 

 must exist. A greater chemical reactivity can thus be argued from anal- 

 ogy with other nascent substances. The ease with which aniline is oxidized 

 in the sunlight in the presence of oxygen with the formation of quinone 

 condensation products, and the rapidity with which azophenine is formed 

 in the sunlight in the absence of oxygen, argue strongly in favor of the 

 view that there is a labile hydrogen atom with a well-defined tendency to 

 vibrate in an equilibrium which can be represented by the Dewar for- 

 mula 24 thus 



NH„ NH 



H 



The formation of the groups : 



H, 



N- 



-HN- 



and 



from aniline either in the presence or absence of 



oxidizing agents under the influence of sunlight, which show a marked 



21 In this connection it may be well to recall that the various formulae pro- 

 posed for the benzene nucleus merely represent phases in the motion of the 

 molecule. The introduction of groups into the benzene nucleus may change the 

 condition of the ring itself. ( Kauff mann et. al. have published a series of articles 

 entitled "Undersuchungen. tiber das Ringsystem des Benzols". Ber. d. deutschen 

 Ghem. Ges. (1900), 33, 1725; Hid. (1901), 34, 682; Ibid. (1902), 35, 3668; 

 Ibid. (1903), 36, 561; Ibid. (1904), 37, 2612, 2941; Ibid. (1905), 38, 789, 

 794; and "Electronentheorie u. Valenzlehre", Phys. Ztschr. (1908), 9, 311. 

 Benzene may be regarded to have the Baeyer-Armstrong, 



the Kekul6, 



or the Dewar formula 



The first condition is aliphatic, as in nitrobenzoic acid, C 6 H 4 . N0 3 . COOH, the 

 second is aromatic as in the phenols and the third is typified by aniline, p-phenyl- 

 ene diamine, naphthalene and anthracene. 



