912 REPORT—1904. 
The second asymmetric carbon atom is not inverted, and no /-camphoric 
acid is produced, It is therefore possible, by merely converting into an 
anhydride, to restore completely the original activity of the acid. 
In d-tartaric acid both active carbon atoms can be inverted, giving 
rise to meso-tartaric and /-tartaric acids. The rate of formation of the 
meso- acid from the d+/ acid in presence of hydrochloric acid at 140° 
is 1:9 time as great as that of the d+/ from the meso- acid, and 
the proportions in the equilibrium are therefore those indicated in the 
equation 
Wi H ,CO.OH HO. 00.0H 
Hise) 19 Ose. at Nea Yd 
SeOMHS y= pr ee | NH 
| CO.0H = | (COOH, = AM 
Cx Cx Cz 
Ho’ ~ NH HO? HO’ ~ \CoOH 
d-acid 17:33 % meso- acid 65°4 % l- acid 17:3 % 
The formation of the meso- acid involves a double, and that of the /- acid a 
quadruple keto-enolic change, and the conversion is therefore exceedingly 
slow, the proportions after heating during 42 hours at 155° being only 
3°4%1 : 18 % meso : 78:6 %d.' The salts undergo similar isomeric 
change when heated with an excess of alkali, but the proportions when 
equilibrium is reached appear to be 38 % / : 24 % meso : 38 % d. 
The reversible isomeric change which glwconic and allied acids undergo 
when heated with quinoline or pyridine at 130°-150° ” is of importance, not 
only in the synthesis of the sugars but also because of the proof it affords 
that a definite mechanism is needed to bring about optical inversion, and 
that apart from this it is impossible even to interchange the points of 
attachment of an H and OH group. In each case only the terminal 
CHOH group which carries the carboxyl is inverted, whereas if it were 
possible by this drastic treatment to shake the remaining CHOH groups 
the product would be a chaotic mixture of the sixteen acids which are 
theoretically possible. 
Closely related to the isomeric changes of the sugar-acids are those 
which the hexoses themselves undergo in solution, and especially in 
presence of alkalies. Glucose appears to exist in four isodynamic forms,’ of 
which the stereoisomeric a and f (hydrogen-) glucosides are the dominant 
forms and the aldehyde a minor constituent, the enol being present only 
in traces. Owing to the moderate proportion of aldo-glucose present in- 
the solution equilibrium is rapidly established between the a and B gluco- 
sides. The enolic form is common to glucose, fructose, and mannose, and 
the slow rate at which equilibrium is established between these three 
sugars, even in the presence of considerable quantities of alkali,‘ is an 
1 Holleman, Rec. Trav. Chim. 1898, 17, 66. 
2 Fischer, Ber. 1894, 27, 3193. 
3 Compare Zrans. 1903, 83, 1314. For the proof that the a and B glucose are the 
parent substances of the « and £ glucosides, see E. F. Armstrong, Vans. 1903, 83, 1305, 
and Behrend and Roth, Ann. 1904, 331, 359. With reference to the proportions of the 
constituents in the mixture, see Lowry, Proc. 1904, 20, 108, For the dynamic 
isomerism of the methyl glucosides and of the pentacetates, see Jungius, Proc. Kon. 
Akad. Wet. Amsterdam, 1904, 99 and 779. 
4 Lobry de Bruyn, Rec. Trav. Chim. 1895, 14, 201, 
