39 § LABILITY AND ENERGY IN RELATION TO PROTOPLASM. 
But not only does 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 cliacetone-amine, or the pinylamine of 
Wallach , and in other cases is readily replaced by hydroxyl, as 
in the amides of acids. Of the y-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 modification. 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- 
thoquinone-imide exists in two forms, a red one, stable in alkaline 
solution; and a light yellow one, stable only in acid solution. (4) 5 
Claisen® y 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 present.” 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) Bcr. Cliem, 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 
nitrosonaphthol (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) Kellermann and Hertz, Ber. Chem. Ges. 29 , 1145. 
(5) Ibid. 29 , R. 499. 
(6) Wisliccmis, Ibid. 29 , R. 503. Brühl, Ibid. R. 484. In this case the aldo- 
modifioation has a decidedly acid character, while in the above mentioned case of 
Claise?i it is the enol-modification. 
