444 TRANSACTIONS OF SECTION B. 
thus able tu show that both monomethyl- and dimethylglucose conform to the 
generalisation established by C. S. Hudson ‘ regarding molecular rotation in the sugar 
group. As the two sugars are substituted respectively externally and internally to 
the y-oxidic ring, it would appear that Hudson’s rule is applicable to certain types of 
substituted sugars and can be used for calculating the activity of unknown 8 forms 
or for the adjustment of approximate values determined experimentally. On this 
basis the specific rotation of 8-tetramethyl glucose becomes +-32°-16, a value which is 
consistent with the rotatory powers of the fully alkylated glucosides. Hudson’s rule 
cannot however be applied to benzylidene methylglucoside, a new isomeric form of 
which was isolated, on account of the introduction of a new asymmetric system into 
the molecule. 
Our results also show that the hydroxy] groups in glucose fall into two classes with 
respect to their influence on optical power, (a) those situated within the y-oxidic ring, 
and (6) those external to the ring. In class (a) the asymmetric systems in which the 
hydrogen atom is above, and the hydroxyl group below the plane of the ring, exert a 
dextro-rotatory effect. Those in which the reverse arrangement exists are levo- 
rotatory. Definite configurations can thus be suggested for the a- and 8-glucoses. 
The effect of methylating the hydroxyl groups of class (a) is to greatly intensify 
the rotation of the system to which it belongs, while in class (b) the effect is relatively 
small, If the groups are numbered according to the scheme :— 
O 
| | 
CH,OH - CHOH - CH - CHOH - CHOH - CHOH 
(6) (5) (4) (3) (2) (1) 
the deduction can also be made that the optical effect of methylating the hydroxyl 
group No. 2 is to raise the rotation of glucose by an unknown amount (x) which is 
probably over 100 per cent. 
Methylation of No. 3 depresses the dextro-rotation to the extent x+-20-7 per cent. 
On the other hand, methylation in positions 5 and 6 contributes a rise in the dextro 
sense to the extent of 48-9 and 8 per cent. respectively. ‘These numbers are arrived 
at by adopting as the standard of comparison in each case the value 
[M], a-form + [M], 8-form. 
2 
The application of these quantitative results is now being tested in the case of 
partially alkylated mannoses and galactoses. 
4. Acetyl-halogen Sugar Derivatives. 
By W. Stoan Mus, M.A., D.Sc., B.E. 
Acetyliodoglucose and acetyliodogalactose were prepared by me at Queen’s 
College, Galway, and formed part of a thesis presented for a D.Sc. degree to 
the Royal University of Ireland in 1906. As they were not published by me, 
Fischer has recently described® the former compound which he prepared, how- 
ever, by a more indirect method. 
Preparation of 8-acetyliodoglucose, C,H,O(OAc),I.—Hydriodic acid gas 
was generated by the action of water on iodide of phosphorus and dried by 
means of calcium chloride and phosphorus pentoxide. A slow stream of the gas 
was passed into a solution of five grams of B-pentacetylglucose in 8 c.c. of dry 
methylene chloride contained in a small distilling-flask. The gas was rapidly 
absorbed at first, and when fumes began to issue from the side-tube of the dis- 
tilling-flask the supply was cut off and the side tube directly connected with a 
vacuum pump. The bulb was immersed in warm water till the methylene 
chloride and excess of hydriodic acid had distilled off. The thick syrup remain- 
ing solidified on being touched with a glass rod moistened with alcohol. Jt 
should be recrystallised as quickly as possible from the alcoholic solution, as 
both methyl and ethyl alcohol decompose it, the solution becoming acid. 
It melts at 108° to 109° and readily yields acetyl acoholic and acetyl phenolic 
glucosides. Various attempts were made to prepare a-acetyliodoglucose from 
a-pentacetylglucose, but in all cases the 8 compound was isolated. 
4 Journ. Amer. Chem. Soc., 1909, 31, 66. 5 Ber, 48 (1910), 2521. 
