ON OPTICAL ROTATORY DISPERSION. 
263 
In the case of nitrocamphor, only one form of the parent substance is known, 
although derivatives of both types have been prepared, including dextrorotatory salts, 
such as 
C:NO. ONa 
C,H„< | 
CO 
and a dextrorotatory anhydride 
,C:NO.O.ON:a 
c 8 H ]4 < 
>C S H 
'CO 
oc / 
8 J ~ L 14 
derived from the acidic pseudo-form of the nitro-compound. 
In the case of 7r-bromonitrocamphor, however, both isomers have been isolated and 
have been found to change in opposite directions to an equilibrium mixture of 
intermediate rotatory power {ibid., p. 225). 
.CH.NO* XkNO.OH 
C 8 H 1; 3< I t C 8 H 13 Br ; I 
x CO x CO 
Nitrocamphor agrees with tartaric acid in that its optical rotatory power is 
exceptionally sensitive to changes of conditions, no doubt in part as a result of the 
displacement of the point of equilibrium, e.g., in different solvents. As in the case of 
tartaric acid, the rotations may even exhibit a change of sign under some extreme 
conditions; thus in certain oxygenated solvents nitrocamphor, which is usually laevoro- 
tatory, gives small dextrorotations, just as dextro-tartaric acid, when dissolved in an 
excess of alkali, may give small hevorotations (see pp. 280-282 below). 
It is, however, characteristic of nitrocamphor that it is able also to give derivatives 
of fixed type (compare the conversion of prussic acid into methyl cyanide and methyl 
isocyanide) in which the plasticity of the parent substance has disappeared. Thus by 
chlorination nitrocamphor is converted into two derivatives of the normal nitro type, 
whilst in the formation of the anhydride and of the salts a complete conversion into 
the acid pseudo-nitro type takes place. The chloro-nitrocamphor corresponding to 
nitrocamphor itself gives [a] D —5° in chloroform, whilst the anhydride gives [a] D -f- 167° 
in chloroform. 
In the case of tartaric acid, it has been less easy to discover fixed derivatives to 
correspond with these compounds, since (as has already been noted) the esters show 
just the same anomalies as the acid itself, and any molecular rearrangement which 
involves the hydrogen atoms of the carboxyl groups is therefore ruled out as an explana¬ 
tion of the flexible rotatory power of the acid. Biot in 1835 ( ; Comptes Rendus,’ 1835, 
vol. 1, pp. 458-459) appeared to have found a solution of this problem when he stated, 
in his sealed note to the Academy, that “ The combinations of tartaric acid with solid 
bases, also with boric acid, give products endowed with rotation towards the right; 
