393 LABILITY AND ENERGY IN RELATION TO PROTOPLASM. 



But not only docs the lability of these hydrogen atoms vary con- 

 siderably in different compounds, that of the entire amido-group 

 also does so, and the latter is, in some cases, easily split off as 

 ammonia, as in the case of diacctone-amine, or the pinylamine of 

 Wallach, and in other cases is readily replaced by hydroxyl, as 

 in the amides of acids. Of the ^-amido-acids the amido-group 

 is also said to be easily removed with the formation of lac- 

 tones. (1) The relative position of the amido-group also exerts 

 a powerful influence upon the special character of a compound ; 

 thus ortho and para-amido phenol are stronger bases than aniline, 

 while meta-amidophenol is a weaker one, than aniline/ 2 ' 



Of special interest is the transition of a labile compound into a 

 stable mollification. In certain cases the latter can easily be re- 

 transformed into the former, in others it is difficult. Of nitro-para- 

 aceto-toluide a yellow and a colourless modification exist ; the 

 former is more stable at a high temperature than the latter but 

 can easily be retransformed into it/ 3 ' The oxime of oxynaph- 

 thoquinonc-imide exists in two forms, a red one, stable in alkaline 

 solution; and a light yellow one, stable only in acid solution/ 4 ' 



Claisen' 5) infers from his investigations on I. 3 diketones that 

 some of them may exist in two modifications, viz., as 

 . C(OH) : C • CO . and . CO ■ CH ■ CO . " It depends upon 

 the nature of the attached radicals, the temperature, the nature of 

 the solvent, which of the two forms is the more stable under the 

 conditions jjresent." Two isomeric forms of the formyl-phenyl- 

 acetic ether have been isolated which can easily pass one into 

 the other, the liquid or ^-modification corresponds to the enol 

 (hydroxyl-) structure, the solid or /^-modification to the 

 aldo-structure. (6) The former which alone gives a blue violet 



(1) Ber. Chem, Ges. 17, 203. The replacement of an alcoholic hydroxyl group 

 by an amido-group is only in certain cases easily accomplished, as in cyanhydrines, in 

 nitrosonaphlhol (Ber. 17, 393) and in the ortho-nitro-derivative of the phenyl-/3- 

 oxypropionic acid {Einhorn, Ber. 16, pp. 2645 and 2651). Evidently the influence of 

 a negative group is required for enabling such an exchange. 



(2) Lellmann and Gross, Ber. Chem. Ges. 24, R. 107. 



(3) Gattermann, Ber. Chem. Ges. 23, 1733. 



(4) Kellertnann and Hertz, Ber. Chem. Ges. 29, 1 145. 



(5) Ibid. 29, R. 499. 



(6) Wislicenus, Ibid. 29, R. 503. Briihl, Ibid. K. 484. In this case the aldo- 

 modifieation has a decidedly acid character, while in the above mentioned case of 

 Claiscn it is the end-modification. 



