On the Classification of Carbon- Compounds. 
311 
The tendency to form water is explained by the following 
thermochemical equation: 
(H 2 ,0) = H 2 0 vapor. .+57.2 calories, or 
(H 2 ,0) = H 2 0 liquid at 16° C.+68.3 calories. 
There are striking exceptions to this rule, and as a striking 
exception the formation of chloral hydrate from anhydrous 
chloral may be mentioned. The reaction expressed by the fol- 
lowing equation, CCl 3 C n + H =CC1 3 C—O —H, is an ex- 
& ^ O—H \0—H 
othermic one. It must also be granted that e. g. formic alde- 
hyde C - H in aqueous solution, at least, may have the formula 
O—H 
^/LO —H 
’ 
X H 
i. e., formic aldehyde plus water, in which the 
hydrate must not be considered as a molecular addition pro- 
duct of H 2 0 to C—H, written C—H+H 2 0, but as the dia- 
VH \H 
/O-H 
tomic alcohol, methylene glycol 
X H 
The synthesis of a number of carbon compounds cannot be ex¬ 
plained without this assumption. As .examples, the syntheses 
of penta-erythrite and of several of the sugars may be men 
tioned. The former results form a condensation of formic and 
acetic aldehydes according to the following equations: 
^H 9 
C—0—H 
1 
10—Hi 
i+: 
i H i 
: H 2 
i 
■i 0—H+H 
—C— H4-H-0: 
•0— H 
o- 
/1 \ 
COM 
1 1 
MW 
^h 2 
3—O- 
-H 
CH 2 OH 
i 
= HOHoC—C—CHoOH 
l/H 
C—O—H 
\0—li 
+3H 2 0. 
