Standard solutions of formaldehyde were prepared in the acidified ethanol (1% p-toluenesulfonic acid
The coupling catalyzed by p-toluenesulfonic acid
gave a complex mixture, since norlichexanthone (2) has four free positions for this reaction, and in each possible product, more than one position of the phenolic moiety can attack the electrophile.
The hydrogen peroxide, ferric chloride crystal (Fe[Cl.sub.3]-6[H.sub.2]O), polyethylene glycol 400 (PEG-400), p-toluenesulfonic acid
(p-TSA) and orthodichlorobenzene at analytical reagent grade were obtained from Shanghai Chemical Company (China) and used as received.
(0.1 w/v% with respect to the weight of the reactants) was added as the catalyst.
Diethylene glycol, p-toluenesulfonic acid and paraformaldehyde were used as received without purification.
Diethylene glycol (48 ml), 15 g of paraformaldehyde, and 0.05 g of p-toluenesulfonic acid were added to a flask containing 100 mi toluene.
In both cases, the S[O.sub.3] groups are coupled with the polymer chains in a different way that found in polyaniline doped with p-toluenesulfonic acid, where S[O.sub.3] groups display ionic interactions with the polymer chains.
Sulfonated polyaniline (SPAN), polyaniline doped with p-toluenesulfonic acid (PAni[.sub.TSA]) , and polyurethane from castor oil were used to produce the different kinds of membranes.
The derivatives used were the hydrochloric acid, sulfuric acid, stearic acid, p-toluenesulfonic acid, and methane sulfonic acid salts and the methyl iodide quaternary ammonium salt.
However, the efficiency factors shown in Table 2 clearly show that on a molar basis, the methane sulfonic and p-toluenesulfonic acid salts were the most effective plasticizers.