396 LABILITY AND ENERGY IN RELATION TO PROTOPLASM. 
discussion of the energy of aldehydes it may be worth while to 
p-ive a series of cases which show how much various atomic 
groups and their relative positions can influence the stability of 
compounds which ranges within very wide limits. (1) While, e.g., 
certain substances easily resist higher temperatures, as benzene 
and pyridine, others are decomposed by boiling water, as aceto- 
acetic acid ; others again change even at low temperatures, as 
cyanic acid or diamido-acetone. 
As a general rule it may be considered that the increase in 
number of hydroxyl or amido-groups , as also the alternation of 
positive and. 7iegative groups , depresses the degree of stability. 
Glycerol is less stable then propyl alcohol ; di- and triamido- 
benzenes much less so than mono-amido-benzene i.e. aniline. 
Diketohexamethylene is less stable than dioxyhexamethylene 
( Baeyer ), and acetoacetic acid less so than pyruvic or acetopro- 
pionic (lævulinic) acid ; but it becomes more stable by the intro¬ 
duction ol one more carboxylic group. 
CH 3 
I 
CO 
I 
ch 2 -cooh 
— - —^ 
Aceto-acetic acid 
CH,-COOH 
I 
CO 
I 
ch 2 -cooh 
Acetone-dicarboxylic acid (2) 
CH 3 
I 
CO-COOH 
Pyruvic acid 
CH 3 
I 
CO 
I 
ch 2 
I 
ch 2 -cooh 
— — "V 
Lævulinic acid 
The increase in number of carboxylic groups considerably 
diminishes the degree of stability in such cases in which two of 
these groups are linked to the same carbon atom. With the 
(1) In stable chemical compounds the atoms are placed in comparatively fixed posi¬ 
tions relatively to each other and a change is not brought about except by relatively very 
energetic actions. 
(2) The ratio of positive to negative groups is in aceto-acetic acid 2 : 2, while in 
acetone-dicarboxylic acid it is 2 : 3. This difference may account for the greater stability 
of the latter. 
