hydroxybenzoic

From the point of view of the chemistry of the tannins, therefore, the starting-point would naturally be that of synthesising the ester anhydrides of hydroxybenzoic acids.

Synthetic Tannins Georg Grasser

If the carboxyl of the first molecule combines with a hydroxyl of the second molecule (ester formation), then a substance possessing character similar to that of a hydroxybenzoic acid is formed, which is capable of combining up with a further molecule in the same way.

Synthetic Tannins Georg Grasser

They readily form esters with alcohols, which on subsequent saponification with alkali are converted into the esters of the free hydroxybenzoic acids.

Synthetic Tannins Georg Grasser

Of the three classes of isomeric anhydrides which can be formed from hydroxybenzoic acids, the chemistry of the natural tannins is only concerned with the class comprising the ester anhydrides.

Synthetic Tannins Georg Grasser

This simple procedure, however, is not applicable to most other hydroxybenzoic acids which are decomposed at the high temperature necessary to induce reaction.

Synthetic Tannins Georg Grasser

These investigators found that by the condensation of phenols and hydroxybenzoic acids with formaldehyde, diphenylmethane derivatives were formed; pyrogallol yields hexahydroxydiphenylmethane --

Synthetic Tannins Georg Grasser

Similarly to sugar, the true glucosides can be coupled with hydroxybenzoic acids, which is proved by the preparation of tetra-galloyl - [Greek: a] - methyl glucoside; this substance, also, exhibits tannoid character.

Synthetic Tannins Georg Grasser

The production of synthetic tannins employs two quite distinct methods; one is to synthesise the most simple tannin, viz., the tannic acid contained in galls (tannin), or to build up substances similar in character to the tannins, from hydroxybenzoic acids.

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

The chlorides, being for the most part solids, the mode of procedure is as follows: -- the hydroxybenzoic acid required for coupling is dissolved in normal or double-normal alkali (the volume calculated per molecule acid), a little acetone added, and the mixture well cooled;

Synthetic Tannins Georg Grasser