= 
PNexd: ae patatory Giopersion of /-menthone was Y detennidad: in the Same manner 
ir various: organic solvents. It would lead much too far to quote here the values found 
Ww ith each of the solvents, so we must confine ourselves to characterize briefly the 
ir fluence of some of the solvents, and state merely that with a concentration of 
5g. ‘menthone in 100 cc. the specific. angles of rotation lay, with red light, between 
—13 and — 25° and with violet light between — 35 and -— 60°. The quotients of 
dis persion with /-menthone ranged between 2.16 and 2.80. 
Ta Benzene and toluene cause a marked reduction in the rotatory power compared 
vith the rotation of pure /-menthone. In toluene, the dispersion quotient is the largest 
all observed with this ketone at ordinary temperature, with exception of those cases 
where inversion. takes place. The influence of alcohols on the rotatory power of 
i-menthone seems not to be very great, and in ether, the rotation was even nearer to 
‘that of the undiluted ketone than in dilution with alcohols. Benzaldehyde ‘manifested 
nO strong influence on the rotation which, on the whole, was lowered. The values 
" ound in acetone solution resemble those observed _in ether and es the values 
found with the pure ketone. i 
_ Since Beckmann’s investigations have shown that some inorganic elas: causé in- 
version of /-menthone, the authors studied the influence of numerous acids.~ However, 
% at ordinary temperature no inversion took place with acetic, propionic, n-butyric aad 
4so-butyric acids, formic acid being an exception. The acids lower the specific rotation 
of the ketone, although not so marked as does benzene. The influence of acetic an- 
hydride on the rotatory power of /-menthone is. even less than with acetic acid; 
ethyl acetate and in ethyl acetoacetate solution, the rotation differs Ny from a, 
r otation of the pure ketone. , 
The halogenated compounds: chloroform, symm. Pailoractnylene trichloroethylene, 
é-dichlorobenzene, and bromobenzene do not act in the equal sense on the rotation 
of menthone. Di- and trichloroethylene are of hardly any greater influence than for 
. i Binet: ethyl alcohol; the chloro derivatives of benzene cause a depression in the 
rotation, whereas chloroform raises the specific rotation by nearly 13 percent. Thus, 
x hloroform shows an influence opposite to that of all other solvents investigated which 
lower the rotation more or less. 
' The solutions of menthone in aniline and dineteylanitine were difficult to investigate 
since they soon turned brown. Of nitrogenous bodies, the following were examined: 
Ya iiline, dimethylaniline, nitrobenzene, benzyl cyanide, and pyridine, Nearly all of 
them give rise to a marked reduction of the rotatory power, with the sole exception 
f nitrobenzene. Carbon Hesyipaids is of holy little influence on the eperiie rotation 
4 menthone.. 
SA numerous publications on the so-called inversion of -menthone are dealt with 
"critically by the authors. They are of opinion that hitherto an exact proof was missing 
as to the fact that the inversion-products of -menthone with different rotation are not. 
optical antipodes. Difficult as the proof by chemical means may be, it is a very easy 
one by physical, i.c. optical means, the measuring of the rotatory dispersion of /- and of 
‘| the ‘so-called /-menthone giving the most certain evidence that the two optical isomerides 
are completely different, whereas the agreement, in yellow light, is. a mere chance. 
The authors then prepared, with special caution, a dextrorotatory menthone (Il) 
-Beckmann’s directions; a preparation (I) beaded under the conditions originally 
a. svised by Beckmann showed a lower sotation. In addition they examined a third 
menthone (III) handed over to them by other investigators. The values observed with 
| tk ese three inde es show evidently tat none of these dextrorotatory menthones is the 
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Berea er NOTES ON SCIENTIFIC RESEARCH. en MEes Ces S99. 
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