36 CHEMISTRY OF PLANT LIFE 



Hexoses 



Mannitol series Dulcitol series 



Aldoses d- and Z-Glucose d- and /-Galactose 



d- and Z-Mannose d- and Z-Talose 



d- and Z-Gulose 

 d- and Z-Idose 



d-Altrose 

 d-Allose 



Ketoses d-Fructose d-Tagatose 



d-Sorbose 



Heptoses (C 7 Hi 4 O 7 ) Octoses (C 8 Hi 6 O 8 ) Nonoses (C 9 Hi 8 9 ) 



Glucoheptose Gluco-octose Glucononose 



Mannoheptose Manno-octose Mannononose 



Galactoheptose Galacto-octose 



Persuelose 



Sedoheptose 



The hexoses are by far the most important group of monosac- 

 charides. They are undoubtedly the first products of photo- 

 synthesis, and all the other carbohydrates may be considered to 

 be derived from them by condensation. Because of their bio- 

 chemical significance and their immense importance as the fun- 

 damental substances for all plant and animal energy-producing 

 materials, the following detailed studies of their chemical compo- 

 sition and molecular configuration are fully warranted. 



That all the hexoses contain five alcoholic groups is proved 

 by the experimental evidence that each one forms a penta-ester, 

 by uniting with five acid radicals, when treated with mineral or 

 organic acids under proper conditions. Thus, glucose penta- 

 acetate, penta-nitrate, penta-benzoate, etc., have all been pre- 

 pared. The presence of the aldehyde group is proved by the fact 

 that all aldohexoses have been converted, by gentle oxidation, 

 into pentaoxy-monobasic acids, and the ketohexoses broken down 

 into shorter chain compounds by similar gentle oxidations; these 

 reactions being characteristic of compounds containing an alde- 

 hyde and a ketone group respectively. This experimental evi- 

 dence establishes the nature of the characteristic groups in the 

 molecule, in each case. 



The molecular configurations illustrated in the following table 

 are those suggested by Emil Fischer, as a result of his exhaustive 



