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isomeric gulose; only the formula I B a admits of such an isomer, and therefore the configuration of mannose and gulose, of mannosaccharic and saccharic acid, is at once settled, as well as that of the corresponding mannite and sorbite, which are formed on reducing mannose 2 and glucose 3 respectively.

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At the same time this determines the configuration of levulose. The constitution is, according to Kiliani, H2COH(HCOH),COCH2OH. Now, as this yields on reduction sorbite and mannite 1 :

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it must possess the third formula.

Glucose group, mucic acid derivatives. Since it is

1 Fischer, Ber. 24, 521.

2 Ber. 22, 365; 24, 539.

3 Meunier, Delachanal, Compt. Rend. 111, 49, 51.

4. Ber. 23, 2611.

proved that mucic acid, CO2H(HCOH),CO2H, and the corresponding dulcite belong to the inactive indivisible type,' we have only to choose between the two following configurations for the acid:

1

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2

(and galactose), two possibilities. Now, this acid is converted into talonic acid (and talose) by heating the quinoline- and pyridine-salt, and the transformation must be supposed to take place in the HCOH group next to the carboxyl. Talonic acid is accordingly :

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But this determines the configuration of the talomucic acid obtained by oxidation. Of the four active types we have now determined three, saccharic acid by the configuration of glucose, mannosaccharic

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2. That globose, by means of its osazone, can be changed into levalose?

5. That mannite forms on oxidation mannose and jevclose.*

4. That glucose, on being treated according to the method of Kiliani-Fischer, gives a glucoheptonic acid in two isomers, of which one forms on oxidation an inactive, indivisible pentoxypimelic acid,3 and so

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CHAPTER V

THE UNSATURATED CARBON COMPOUNDS

I. STATEMENT OF THE FUNDAMENTAL IDEA

Historical. In planning this chapter for the new edition, it was of special importance to make plain the present position of the theory.

Having hitherto considered chiefly the derivatives of methane, CH, we have now to do with those of ethylene, C2H. The problem is here more complicated, since there are now six atoms whose relative position is to be considered, whereas before there were only five; and accordingly we find the position of affairs less satisfactory.

With regard to the asymmetric carbon atom, Le Bel's conceptions and mine led to the same result. There was here at least the possibility of a difference. My fundamental idea was the tetrahedral grouping, that is to say, any force-cause so far unknown--proceeding from the carbon atom and tending to drive the groups united with carbon as far away from one another as possible, that is, to bring them into the tetrahedral position. Although it did not necessarily follow that the tetrahedron must be regular because the mutual action of the different

2. That glucose, by means of its osazone, can be changed into levulose.1

3. That mannite forms on oxidation mannose and levulose.2

4. That glucose, on being treated according to the method of Kiliani-Fischer, gives a glucoheptonic acid in two isomers, of which one forms on oxidation an inactive, indivisible pentoxypimelic acid,3 and so

on.

2 Dafert, ibid. 17, 227.

1 Ber. 22, 94.

3 Fischer, Ann. 270, 64.

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