Dimethoxybenzoic Acid Research Articles

Interaction of metal ions with humic-like modelsX. Synthesis, spectral properties and thermal decomposition of copper(II) methoxy- and dimethoxy-benzoates

Cu(II) complexes of 2-methoxybenzoic acid (MBH), 2, x-dimethoxybenzoic acids (2, x-DMBH; x = 3, 4, 5 and 6) and 3, y-dimethoxybenzoic acids (3, y-DMBH; y = 4 and 5) have been prepared and characterized by spectroscopic methods. They involve tetracarboxylate bridged dimeric arrangements of the copper(II) acetate monohydrate-type. The thermal decomposition of such complexes has been studied by thermogravimetric measurements and spectroscopic as well as mass spectrometric analysis of the evolved products and the intermediate residues. A mechanism which involves the shift of a CH 3 group from a ligand molecule to the carboxylic group of a second ligand, to give the methyl ester of the parent methoxy- or dimethoxy-benzoic acid, has been substantiated. Simultaneously, monomeric copper(II) complexes involving a 1 : 1 metal to ligand ratio and metal coordination by a carboxylate and a phenolate group are formed in the residues.

Benzocyclobutenes. Part 5. Synthesis of 4-hydroxy-, 4,5-dihydroxy-, and 3,6-dihydroxy-benzocyclobutene-1,2-dione (benzologues of semisquaric and squaric acid)

4-Methoxy- and 4,5-dimethoxy-benzocyclobutene-1,2-dione have been made by flash vacuum pyrolysis of the anthracene adducts of the corresponding phthalazine-1,4-diones which were prepared from the appropriate methoxyphthalic anhydrides. 3,6-Dimethoxybenzocyclobutene-1,2-dione has been prepared from 2-amino-3,6dimethoxybenzoic acid via the addition of 3,6-dimethoxybenzyne to vinylidene chloride followed by hydrolysis of the resulting 1,1-dichloro-3,6-dimethoxybenzocyclobutene, bromination, and further hydrolysis. The three methoxy-diones and 4,5-dimethoxyphthalaldehyde have been demethylated by heating them with hydrobromic acid and the pKa values of the four hydroxy-compounds have been measured. Preliminary experiments on the synthesis of 4,5-dimethoxybenzocyclobutene are recorded.