( 145 ) 
Isodialdane contains no unsaturated bond, bromine is not taken up 
and alkaline permanganate is not decolorised. The two hydroxyl 
groups of the two aldole molecules have disappeared; the solutions 
in benzene and xylene giving no hydrogen when boiled with sodium 
and acetic anhydride and sodium acetate having no action on iso- 
dialdane even on boiling; acetic anhydride with a trace of sulphuric 
acid or of zine chloride gave rise to resinous products from which 
an acetate could not be separated. The application of SCHOTTEN— 
BauMANN’s reaction with benzoylchloride also gives a negative 
result. Phenylhydrazine is quite without action even after boiling 
the alcoholic solution, so that a carbonyl group is not present in iso- 
dialdane. Sodium amalgam does not effect reduction or acts very 
slowly, since after four days reaction, partly at the temperature of 
the boiling water bath, almost the whole of the isodialdane was 
recovered unchanged. 
We consider that the structural formula, which satisfactorily re- 
presents the results obtained, must be that in which each of the 
three oxygen atoms still present in isodialdane are supposed to be 
connected to two carbon atoms. 
This leads to the hypothesis that two aldole molecules 
GH, CH, 
| | 
CHOH CHOH 
| | 
orto 
| | 
OE 
Cy. of 
lose one molecule of water, yielding 
CH, CH, 
| | 
CH—0—CH 
| | 
CH, CH, 
| 
| 
rns we 
This system is apparently very stable, except under the action of 
dilute acids. 
11* 
