ANODIC-OXIDATION OF 2,6-DIHYDROXYNAPHTHALENE AND STRUCTURAL CHARACTERIZATION OF THE OLIGOMERS

Potential-controlled electrochemical oxidation of 2,6-dihydroxynaphthalene (1) produced two oligomers, which were characterized by spectrometric (H-1 and C-13 NMR, IR, and UV) and electrochemical (CV) methods. The H-1 NMR chemical shifts of the peracetyl derivatives, which showed different values for the acetoxy groups attached at the terminal and the internal positions of the chain, were essential for structure determination of the products. Peracetyl derivatives of the monomer 1a, dimer 2a, and two stereoisomeric trimers 3a and 4a served as models in the spectrometric characterization and structure determination of the oligomers. The product isolated from the anolyte was a mixture of oligomers 5 composed of an average of nine monomer units. The spectroscopic data for the product extracted from the anode 6 suggested that its molecular weight was much higher. In all investigated compounds, the naphthalene rings were proven to be linked at the 1- and 5-positions. The solubility and the spectroscopic data of both oligomers suggested that the chains were not cross-linked. Similar cyclic voltammetric (CV) behavior was found for poly(2,6-dihydroxynaphthalene) films prepared either by the dip-coating technique from a solution of 6 or by the previously reported electrochemical deposition from a solution of 1 by the potential-scanning technique.(2)