carbomethoxy

In the presence of AlCl_3 the chlorides easily combine with benzene, and on removing the carbomethoxy group unsymmetrical hydroxy derivatives of benzophenone are formed: --

Synthetic Tannins Georg Grasser

The chlorides may be coupled with free hydroxybenzoic acids, and on removing the carbomethoxy group didepsides are obtained.

Synthetic Tannins Georg Grasser

The substance is dissolved directly in sufficient normal alkali to neutralise the carboxyl group and a further 2 molecules of caustic soda for each carbomethoxy group to be eliminated are added.

Synthetic Tannins Georg Grasser

The elimination of the carbomethoxy group may be brought about by dilute alkaline solutions in the cold, or by aqueous ammonia.

Synthetic Tannins Georg Grasser

The principles underlying the synthesis of depsides are the following: -- If the chlorides of carbomethoxy (or carbethoxy) hydroxybenzoic acids are coupled with the sodium salts of hydroxybenzoic acids, esters are formed, _e. g.

Synthetic Tannins Georg Grasser

The carbomethoxy group is easily removed by excess of aqueous alkali in the cold, and is also partially removed when insufficient alkali is present; the latter fact is of importance in the synthesis of didepsides.

Synthetic Tannins Georg Grasser

The carbomethoxy derivatives of the depsides are as a rule crystalline substances of distinct acidic character, and decompose alkaline carbonates.

Synthetic Tannins Georg Grasser

When the chloride of its carbomethoxy derivative is allowed to interact with _p_-hydroxybenzoic acid in aqueous alkaline solution, in the cold, the alkali salt of carbomethoxy-_p_-hydroxybenzoic acid is formed: -- [Footnote 1: _Ber.

Synthetic Tannins Georg Grasser

Many hydroxybenzoic acids require an excess of chlorocarbonic methyl ester, which then also, to some extent, attacks the carboxyl group; but on dissolving the product in acetone and treating it with bicarbonate the carboxyl group as such is again restored without splitting off the carbomethoxy group. [

Synthetic Tannins Georg Grasser