Optical Properties of Sugar Hydrazones

VotoCek and coworkers confirmed this result and extended it to the p-chlorobenzylphenyl-, benzyl-p-tolyl- and dibenzyl-hydrazones which were found to behave in the same way as the benzylphenylhydrazones. On the other hand the ethylphenyl-, butylphenyl- and diphenyl-hydra-zones as well as the phenyl- 9-phenylethylhydrazones do not follow the rule the presence of a benzyl group or substituted benzyl group seems to be the deciding factor. 

Although, as mentioned previously, other possibilities of isomerism exist, most attention has been devoted to attempts to decide whether sugar osazones are cyclic or acyclic. The results of methylation experiments indicate that under these conditions the osazones react as cyclic structures, but there is less certainty about the structure of acetylated osazones. 

He shows that n-fructose methylphenylosazone in contact with phenyl-hydrazine at room temperature yields n-fructose methylphenylphenyl-osazone and with p-nitrophenylhydrazine, n-fructose methylphenyl-p-nitrophenylosazone. It is possible to interpret this result in another way, namely that since the competing base removes one methylphenyl-hydrazine residue but not both, one is less firmly bound than the other, and might be admitted as evidence that the two methylphenylhydrazine residues are bound by different types of linkage to the sugar, as in fact the cyclic formulation demands. 

The four acetyl groups of the hexose phenylosazone tetraacetates when examined in this way all appeared to be joined through oxygen, and Wolfrom and coworkers concluded, therefore, that these osazone acetates are open-chain compounds. 

Some doubts have been expressed as to whether such a conclusion is justified, on the ground that, if the osazone acetates are cyclic, the fourth acetyl group would be present in an acetylated hydrazide and could not be compared with the acetyl group in such a compound as acetanilide or methylacetanilide. In a.jS-diacetylphenylhydrazine, for example, an amount of acetyl corresponding to about one acetyl group is removed under conditions which would be expected to saponify only 0-acetyl groups. 

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