B.—_CHEMISTRY 33 
camphor both gave an isomorphous mixture of stereoisomeric ««’- and 
«’«-chlorobromocamphors : 
AM aL 
CY“ Cl CCIEY 5, Cr 
CoH | Pre he CoH | Puli Colle. | Nor 
c—O c—O C—O 
a.-Bromocamphor. vy | Chlorobromocamphor. «-Chlorocamphor. 
(Isomorphous mixture.) 
It was then natural to extend the research to the nitro-derivatives (6). For 
this purpose it was necessary not only to nitrate bromocamphor, but to 
brominate nitrocamphor. In this way I first encountered the nitro- 
compound, which has already provided a material basis for two extensive 
series of researches, and has not yet exhausted its utility or interest. 
A NO, NO, 
Ce CY Ge. 
CH | Npr —- CoH | \Br ae Csi | Nu 
C=0 e¢ c=O0 
a-Bromocamphor. ao.’-Bromonitrocamphor. a’-Nitrocamphor. 
The first of a series of happy chances (7) was a measurement of the optical 
rotatory power of a solution of nitrocamphor in the morning, followed by 
a confirmatory reading in the afternoon. During the luncheon interval 
the rotatory power of the solution had become quite different, and I was 
thus presented with a novel example of the phenomenon of change of 
rotatory power with time, which Dubrunfaut had first observed in 1846 
in a freshly prepared aqueous solution of glucose (8). This property of the 
reducing sugars had been variously described as birotation (8), multirota- 
tion, and paucirotation (9), according as the ratio of the initial to the final 
rotation was 2:1, greater than 1 or less than 1; but, since in certain 
_ solvents the szgz as well as the magnitude of the rotation of nitrocamphor 
_ was changed, I suggested in 1899 (10) that the phenomenon should be de- 
_ scribed as mutarotation ; and this name has been in general use ever since. 
The chemical basis of the phenomenon was disclosed by another 
happy accident. Wishing to know whether the change of rotatory power 
could be repeated when the nitrocamphor had been recovered from solu- 
tion, I left a solution in benzene to evaporate on the water bath. Later 
in the day I examined the residue and found that it was now almost 
entirely insoluble in benzene. It had in fact been converted into a new 
compound, an anhydride formed from nitrocamphor by the loss of half 
a molecular proportion of water (11). An anhydride of this type could not 
_be formed directly from nitrocamphor itself, but it could be derived 
_ easily enough from an isomeric hydroxylic form of the substance, such as 
that from which the salts of nitrocamphor were presumably derived. 
: This conclusion was confirmed by the fact that the anhydride of 
: Tevorotatory nitrocamphor was, like the salts, strongly dextrorotatory. 
e 
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