72 
2. by oxidation of cyclohexene with KMnO,, by which a compound 
is formed melting at 99° and which was taken for the trans diol. 
However as this last compound according to experiments executed 
by H. G. Derx, quantitatively yielded an acetone compound, we must 
assign to it the cis configuration ; the diol, melting at 104°, did not react. 
Curiously enough both exercise a small negative influence on the 
conductivity of boric acid, so that in this case the acetone method 
is more reliable than the boric acid method. 
We must however observe that the classic method, based on the 
action of an active isocyanate has not yet been applied. 
So with the eyclopentane diols the configuration has been determined 
in three ways entirely independent of each other; the reliability of 
the borie acid method has been greatly exhanced by this. A close 
study will have to be made of the acetone method. It has the great 
advantage of quickly leading to the purpose; however its drawback 
is, that under the influence of the condensation reagent (HCI) inversions 
are not impossible. 
The determination of the configuration of the cyclic 1-2-diols has 
brought to light the remarkable fact that by the addition of water 
to the oxides not only the expected cis diol is formed, but besides 
and sometimes exclusively the trans-isomer. 
Therefore, if the oxide has a configuration in which the oxygen 
atom lies ontside the plane of the cyclopentane ring, which configu- 
ration in regard to the distribution of matter is the most probable 
one, then the opening of the three-membered ring must have been 
accompanied by an inversion. 
It is remarkable that this inversion with the symmetrical oxides 
of cyclopentene and cyclohexene is almost complete and that under 
all circumstances; on the other side with the asymmetrical indene 
oxide the inversion is dependent on the reaction of the medium. 
A very weak alkaline reaction reduces the quantity of cis diol, 
which is the principal product in acid medium, to zero. 
Attention may be drawn to the fact, that with the reaction in 
alkaline medium, 8 hydrindone (or a condensation product there-of) 
is always formed, so that the alkali seems to loosen the a-CO-linking. 
Indeenoxyd B-hydrindon 
