Glucosazone preparation

Osazone formation. The preparation of glucosazone has already been given (p. 137). It may be carried out on a small scale by either of the following methods, according as (a) the phenyl hydrazine base, or (Z>) one of its salts, is used. 

Osazone formation. Forms an osazone, m.p. 206 (see however footnote, p. 140) this osazone, unlike glucosazone, is soluble in hot water. See p. 139 for preparation. Examine the crystals under the microscope and note the sheaves of plates, not needles (Fig. 63(B),... 

Many of the simpler sugars react after this manner, forming osazones, which have characteristic appearances under the microscope, and are of special value for identification purposes. (J. C. S., 125, 222.) Preparation 249.—Glucosazone. 

Watters, Hockett and Hudson1 have prepared a non-crystalline monomethylmannose which forms an osazone with the same properties as those of 6-methyl-n-glucosazone. The synthesis was achieved by methylation of methyl 2,3,4-triacetyl-a-D-mannopyranoside, followed by hydrolysis. Schmidt and Heiss,13 studying the epimerization of 6-methyl-D-gluconic acid, have claimed to have isolated the phenyl-hydrazide of 6-methyl-n-mannonic acid. 

The identity of the two products not only proves the structure of n-glucosazone formazan, but leaves no doubt that, in the n-glucosone phenylhydrazone prepared by Henseke, the phenylhydrazine residue is attached to Cl. 

The conditions governing the preparation of n-glucosazone fonnazan, and the properties of the product obtained, permit certain conclusions. 

Sugar Osazones, By treatment of sugars with an excess of phenylhydrazine at 100°C., two phenylhydrazine residues are introduced into the molecule, and sugar osazones, difficultly soluble in water, are formed 216), Optimal conditions for the preparation of glucosazone have been determined 217), The reaction proceeds most rapidly in the presence of acetate buffers at a pH of about 4 to 6 in more acid solution (particularly in the absence of air), and with the free base, only the hydrazone is formed 208, 218), The presence of sodium bisulfite in the reaction mixture inhibits the formation of colored by-products 219),... 

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