is a $y OBA: | i yi | 2 
whey 4A v4 aah» 25 He ‘ 
Jae gene a ; . ESFARCH. ‘x 101 
= > se 3 ie LS ede i - \ ¥ j 4 Ds 
e©si SP could “hot he Mieceured” only the final value observed in Vellow light was 
d off: [elo = +38.30°. | ae 
= With. sulphuric acid “monohydrate, /-menthone Sawing aie an intense brown 
cc fe ration and rise in temperature that no optical readings could be taken. Likewise, 
ped and -d-fenchone- turned instantaneously brown in sulphuric acid solution, 
rendering examination impossible. 
es On dissolving a dextrorotatory menthone in sulphuric eid no mutarotation was 
to be observed. This result is opposed to the observations made by Tubandt in 
a alcoholic solution. The. last-named author had even established that the inversion of 
pe eeone by means of sodium ethoxide in alcoholic. solution, proceeds with the 
eact differently. The proposition advanced by Tubandt: “The inversion of menthone 
a. reversible, monomolecular" ‘reaction caused by acids as well as by bases”, must, 
Fis authors’ opinion, be altered insofar that it holds not. good for alcoholic solutions. 
Bs EE was ‘most striking that /-menthone, when dissolved in bromoform, likewise 
re vealed ‘mutarotation, this phenomenon. proceeding even more speedy than in formic 
ai cid- solution. ~ With> chloroform, no: changing of the rotation, after some time, was 
noticed. Hence, the inverting action of bromoform on .menthone might be easily 
made use of for proving the presence of bromoform — in chloroform. The bromoform 
4a sed. was quite neutral. With carvone, it caused no changing of the rotation. Bromo- 
D enzene causes no alteration whatsoever in the rotation, bromal, however, produced 
< Rersion;. which the authors ascribe to its acid reaction. _ 
_ Solutions of l-mehthone in alcoholic potassium hydroxide Showed instantaneously 
dextrorotation, but the latter did not alter on standing. d- -Isomenthone ([«]p +24. 15°), 
BEN, dissolved in alcoholic potash, likewise showed no alteration after some time. © 
4 d-Carvone and d-fenchone turned at once dark when treated with the last-named 
solvent, thus rendering examination impossible. 
Z In alcoholic hydrochloric. acid, PEO OnE showed no mutarotation, dextrorotation 
z sing place instantaneously. — ) 
On boiling with pyridine the rotatory power of Pereaifienc was hardly altered. 
Likewise, higher boiling bases, e. y., aniline, neither caused inversion, nor did prolonged 5 
bo’ oiling with toluene result in any alteration of the rotation of /-menthone. | 
_ Basing on these observations, Grossmann and Brauer consider it. doubtful whether 
the inversion resulting from heating pure menthone is caused, as Beckmann believes, 
the: action of glass. With the object to study the behaviour of pure /-menthone 
B Beating: the ketone was boiled, in a round-bottomed flask of Jena glass, under 
a reflux condenser. Even after 24 hours’ boiling, no alteration of the rotation was 
) be observed, and equally with dextrorotatory menthones the value of the rotation 
a ained practically unchanged after prolonged heating. Likewise, the optical rotation 
of d-carvone underwent, after prolonged boiling under a reflux condenser, only a very 
li sht alteration, a fact proving that carvone does ‘not pare over into Seyi dues on so 
Mu ‘ick as is generally assumed’). . 
Jn addition, the authors eaaéslaed the rotatory. HAAeR ick of the extrbrotatons 
ment ones in alcohol, benzene, and pyridine. These solvents acted insofar differently 
rom /-menthone on dextrorotatory menthone, as they caused a rise of the specific 
ota’ alg and not, as with L-menthone, a ovr: | 
~ 
e velocity as with l-menthone. In alcoholic solution, the d-menthone seems to — 
