pentagalloyl

Careful saponification with excess alkali in acetone-aqueous solution at room temperature yielded a tannin very closely resembling tannin, identified as pentagalloyl glucose.

Synthetic Tannins Georg Grasser

The preparation of pentagalloyl glucose has proved this compound to be nearly identical with tannin obtained from galls (_tannin_); a few other natural tannins belong to this type which Fischer terms acyl compounds of sugar with hydroxybenzoic acids.

Synthetic Tannins Georg Grasser

Considering the very similar structure of these two tannins, such differences appear surprising, but an analogy may be readily found in the existence of colloidal solutions of tannin and the (nearly) identical pentagalloyl glucose.

Synthetic Tannins Georg Grasser

The method of preparation employed in the synthesis of pentagalloyl glucose may be easily applied to other hydroxybenzoic acids, _e. g._ penta [_p_-hydroxybenzoyl] glucose

Synthetic Tannins Georg Grasser

In this connection it should be noted that the calculated molecular weight of pentagalloyl glucose, which in E. Fischer's opinion forms a substantial part of the tannin molecule, is 940, but Fischer also thinks that this compound possesses a much higher molecular weight.

Synthetic Tannins Georg Grasser

The latter is isomeric with pentagalloyl glucose and possesses similar properties; there is, however, a vast difference in the solubility of the two.

Synthetic Tannins Georg Grasser