The apparent simplicity of these processes proved deceptive. The number of chemically definable units increased with accelerated speed from the beginning of the nineteenth century. Toward its end, the very multiplicity which sometimes became confusing made it possible to solve many problems. The genius of the great "natural philosophers" of earlier times had its successors in the genius of chemists who constructed a new unity by fitting together separate pieces of special experience. At first, however, the organismic products had to be taken apart and transferred from a biological system to that of elements and molecules.
In 1827 William Prout (1785- 1850) distinguished between three groups of food materials: fats, proteins, and sugars. From the combustion of sugars which he carried out he concluded that sugars are related to starch and characterized by containing oxygen and hydrogen in the proportions in which these elements are present in water. They are hydrates of carbon, or carbohydrates.
The conversion of starch into the sugar found in grape juice (glucose) was carried out by Gottlieb Sigismund Kirchhoff, a German pharmacist in Russia, in two ways: by heating with dilute sulfuric acid or by digesting with the "gluten" of malt (1811, 1814). Glucose was also obtained by the action of certain specific plant extracts on substances like amygdaline or salicin. Latirent proposed to call these substances "glucosamides" (1852) which Gerhardt simplified to "glycosides." They are split by enzymes into glucose and such complex materials as the nitrile of benzaldehyde (Foster-Powell, K., Brand Miller, 1995).
When Alexander Butlerow (1828- 1886, Kasan) subjected a new substance, which was later found to be formaldehyde, to a digestion with limewater, he obtained (1861) "the first example of the synthetic production of a substance which behaves like a sugar." Baeyer explained this reaction (1870) as starting from a hydrate of formaldehyde, CH 2 ((OH) 2, and consisting of a combination of six such molecules with removal of six molecules of water. The sugar thus had the formula COH(C [OH] H) 4.CH 2 0H. This speculation used the results of an investigation of mannit, an alcohol obtained from manna. Berthelot, as a sequence of his work on the tribasic alcohol glycerine, recognized mannit as a hexabasic alcohol 1860); its reduction to the hydrocarbon hexane, by means of hydroiodic acid, proved the arrangement of the carbon atoms in a straight chain. This proof, in turn, was possible only because of the comparison of this hexane with other hydrocarbons.
A. Wurtz applied his findings of aldehyde condensations, in which only two aldehyde molecules were involved, to the problem of the constitution of glucose. Oxidations to sugar acids and reduction to mannit were further helps in solving the problem. The chemical constitution of fructose, which is combined with glucose in cane sugar (sucrose), could be interpreted (1880) from the acids obtained by oxidizing the addition compound with hydrocyanic acid (Foster-Powell, Miller, 1995).
Cellulose also belongs to the group of carbohydrates, since the addition of molecular water, under the influence of strong sulfuric acid, converts it into glucose (Braconnot, 1819). Wood contains a large proportion of cellulose and lignin. The two call be separated, according to Anselme Payen ( 1795- 1871,