( 7«0 ) 



f'oinerfed into the other eompoiiiid l>v boiling its solution in acetic 

 ;iiili\ th'idc for a short time \v\\\\ a little ZiiClj. 



I have made a closer stiidv ot" this transfoi'mation ; it is caused by 

 an ijdramolecnlar ini,uralioii at the Iciminal asymmetric carbon atom. 

 One might feel disposed to explain the ti-ansformation in an acetic 

 aidivdrifh' solution l)v an addition and subsequent elimination of" 

 a molecide of the solvent, such as Fischer supposed to happen in 

 the mutual transformation of the two isomeric methylglucosides ^). 

 This view, however, becomes untenable as the transformation can 

 also take place without the presence of acetic aidiydride. Then 

 LoBRY DK Bruyn, by sim[)ly melting the (?-isomer m.p. 134° with dry 

 ZnClg, at once obtained the other compound m.p. Ü12^ T also succeeded 

 in causing the same transformation in a chloroform solution containing 

 SOj,. On shaking chloroform Avith fuming sulphui-ic acid, a portion 

 of the SO, jiasses into the chloroform. This solution has been found 

 to accelerate many i-eactions by catalytical action. A solution of 

 the j^-peutacetate in C-HCH, which contained IS. 8 milligrs. ofSO^jjcr 

 cc. at tirst rotated hut slightly to\\ards the riuiit ; afl(M- a short time 

 its I'otatoi'v po^vor had inci-cased. The SO., was now removed by 

 means of dilute alkali and the chloi-oform distilled off. The residue 

 was recrvstallised from alcohol and in this way the pure «-isomer 

 m.p. 1 T2^ was obtained. 



3. As in the case of the \\\o methylglucosides, the tinal con- 

 dition in the transformation between the two stereoisomers is here 

 also an c(|nilibrium : the limit how e\er is situated close to the 

 form melting at 112"'. A solution |>repared by dissolving 5 grams 

 of ;?-pentacetate in 100 cc. acetic anhydride (containing 2 grams 

 of y.iiicchloride) showed an initial i-otatiou of -}" 1 (l>olai'iscoj)e 

 Schmidt and Haknscii: 10 cm. tube). On. keeinng this solution at 

 35°, the rotation increased with measurable velocity and linally ari'ived 

 j^t _|_ 14\o. Ill the case of a (piile similar solution of the /(-isomer, 

 having an initial rotation (»f -|- 16".3 the iiiial rotation was also 

 -j- 14°.5. From this we calculate that in the condition of equiliiirinm 

 tiiere exists SS^/o of the a and 12" „ of the ,i-compoiüid. The former 

 could in fact be isolated in a pui-e condition : in addition also some 

 ci'jstals which melted at 95 — 9S' and contained Ixdh isomei's. 



4. By determining at definite times the said changes in the rotation 

 the velocity of the mutual transformation could be measured. 



It conformed with the formula for the iiuimolecular reversible 



*j Compare my communication, these Proc. June 27, 1903. 



