202 
A complete rotation, as is the case with the saturated non-cyclic 
glycols, is not possible here, as this would mean a continual transi- 
tion from ecis- into trans-diol, and vice-versa, which does not take 
place; besides, the trans-diol gives no trace of an acetone compound. 
How can we now form an idea of the movement in the cyclo- 
hexane diol ? 
In 1890 an extensive study was published by Sacnsr*) on the 
position of the C-atoms in the saturated ring systems starting from 
the premise that the directions of affinity form angles of 109°28’ 
with each other. He proves for the three-, four-, and five-rings that 
the atoms must be situated: in one plane, and that a tension is 
inevitable, which is, however, insignificant for the five-ring. (Von 
Bayrr’s ring tension). He shows for the six-ring that the molecule 
can escape a tension in two ways. First of all the C-atoms can lie 
three in one plane, and three in another, so that the bonds between 
the C-atoms form a zig-zag line. It is, however, also possible that 
four atoms lie in one plane, and two (e.g. 1 and 4, 2 and 5 or 3 
and 6) outside it. 
To bring the molecule out of the first position, a certain resistance 
must be surmounted; the second position is pliable. 
It has been pointed out on different sides that these positions of 
the molecule could not form the image of the stable situation of 
the atoms, because the number of isomers, and particularly of optical 
isomers would then have to be much greater. 
AscHAN *), however, remarks, that these positions are possible 
when they are considered as the successive phases of a system in 
motion. 
This view, indeed, has been confirmed by our boric acid measure- 
ments and the study of the acetone-compounds. 
When we accept the view that the molecules of the six-rings 
move through space as undulatory surfaces, the OH-groups of the 
cis-diol get from time to time into the same plane with and on the 
same side of the C-atoms to which they are attached, and the 
frequency of this occurrence will depend on the most stable state 
of the molecule. 
It is clear that in these undulations repeatedly a symmetric 
position is passed, so that, though the most stable situation is an 
asymmetric one, the separation of optical isomers in liquid state is 
not very well possible; for racemisation will continually set in for 
1) Berichte 23, 1363 (1890). Zeitschr. f. physik. Chemie 10, 228 (1890). 
*) “Chemie der Alicyclischen Verbindungen”, pag. 328—331. 
