200 THE CARBOHYDRATES. 



In order to explain multirotation HUDSON l believes that the aldoses exist in 

 two isomeric forms having different rotation, which on being dissolved pass 

 into each other by means of a reversible reaction. The two forms can be derived 

 because a lactone-like binding exists between the end carbon atom in the alde- 

 hyde group and the 7 -carbon atom according to the formula 



CHoOHCHOH.CH.CHOH.CHOH.C/' . In this way the end carbon becomes 



-o- |X H 



asymmetric and according to whether the position of the atoms that are combined 

 with this carbon atom are: 



we obtain the two forms. TANRET 2 has obtained two isomeric forms of glucose, 

 galactose, arabinose and lactose which pass from one form to the other. The 

 two forms of glucose correspond according to E. H. ARMSTRONG s to the syntheti- 

 cally prepared a- and /3-methyl glucosides prepared by E. FISCHER (see pages 

 61-62). 



Like the ordinary aldehydes and ketones, the sugars may be made to 

 take up hydrocyanic acid. Cyanhydrins are thus formed. These addi- 

 tion products are of special interest in that they make possible the arti- 

 ficial preparation of sugars rich in carbon from sugars poor in carbon. 



As an example, if we start from glucose we obtain glucocyanhydrin 

 on the addition of hydrocyanic acid: 



CH 2 .(OH).[CH(OH)]4.COH+HCN = CH 2 (OH).[CH(OH)]4.CH(OH).CN. 



On the saponification of glucocyanhydrin the corresponding oxyacid is 

 formed. 



CH 2 (OH).[CH(OH)] 4 .CH(OH).CN+2H 2 



= CH 2 (OH).[CH(OH)] 4 .CH(OH).COOH+NH 3 . 



By the action of nascent hydrogen on the lactone of this acid we obtain 

 glucoheptose, CyHuOy and according to this principle the construction 

 of sugars up to nine carbon atoms has been accomplished. 



The monosaccharides give the corresponding oximes with hydroxyl- 

 amine; thus glucose yields glucosoxime, CH 2 (OH).[CH(OH)1 4 .CH:N.OH. 

 These compounds are of importance on account of the fact, as found by 

 WoHL, 4 that they are the starting-point in the formation of one class 



Uourn. Amer. Chem. Soc., 31,. 61, 955 (1909). 



2 Bull. soc. chim., 13, 728 (1895),' 15, 195, 349 (1896). 



3 Journ. Chem. Soc., 83, 1305 (1903). 



4 Ber. d. d. chem. Gesellsch., 26, p. 730. 



