6 



specific rotations of the lactones of the monobasic acids derived 

 from these sugars are (see Table 2), d-arabonic + 74, d-gluconic + 68, 

 d-glucoheptonic 68,d-gluco-octonic + 46. Writing the carbon chain 



rcH 2 oH. c.c.c.c.c.c.cn 



oftheoctose Q\ ^ (3) (4) (5) (g) (7) , it is first noticed that 



as its lactone rotates positive ( + 46) its ring is to be considered as 

 below the chain and joining atom 7 to its ^-carbon 4. This shows 

 that the hydrogen atom on 4 is above the chain. Passing next to the 

 heptose, since its lactone rotates negative ( 68) the hydrogen atom 

 on the new ^-carbon 3 by the same reasoning is below the chain. 

 Similarly the signs of the rotations of the other two lactones show that 

 the hydrogen atom is above 2 and above 1. This determines the 

 stereo constitution of the carbons 1, 2, 3, and 4, and as these are all 

 the asymmetric carbons which occur in the aldehyde formula of 

 glucose, this may be written as follows : 



H H OH H 

 CH 2 OH. C . C . C . C . COH . This formula is identical with 



OH OH H OH 



the one which Emil Fischer has chosen from chemical data alone. 

 The steps of this proof of the structure of d-glucose give also the 

 structures of d-arabinose and d-erythrose. 



The stereo configuration of d-galactose. The cyanid synthesis or 

 its reverse has shown the following series: d-lyxose > d-galactose 

 > d-galaheptose > d-gala-octose, and the rotations of the lac- 

 tones of the corresponding monobasic acids have been found to be 

 (Table 2), d-lyxonic + 82, d-galactonic -78, d-galaheptonic 52, 

 d-gala-octonic + 64. By the same reasoning as given under the pre- 

 ceding section these rotations show that in the stereo formula of 

 galactose the hydrogen atom is above carbons 1 and 4 and below 2 



H OH OH H 

 and 3, giving, CH 2 OH. C . C . C . C . COH . This formula is 



OH H H OH 



identical with the one which Fischer has chosen for galactose. Th' 

 stereo configuration of d-lyxose follows from that of d-galactose. 



The stereo configuration of d-mannose. The cyanid reaction hat> 

 shown the following series: d-arabinose > d-mannose > d-man- 

 noheptose > d-manno-octose, and the rotations of the lactones of 

 the corresponding monobasic acids have been found to be (Table 2), 

 d-arabonic + 74, d-mannonic + 54, d-mannoheptonic 74, d-manno- 

 octonic 44. In the configuration of mannose, therefore, the hydrogen 

 atom is below 3 and 4 and above 1 and 2, giving 



H H OH OH 

 CH 2 OH. C . C . C . C . COH. This is also identical with the 



OH OH H H 

 structure which Fischer has established for mannose. 



[Cir. 49] 



