Acetone pyrrole 1-oxides

Solubility - The oxidized polymer (VIII) has a greater solubility than the original polymer (VII). It was found to be soluble in acetone, chloroform, benzene, DMF and DMSO. Unlike the polymer (VII), (VIII) was not soluble in formic acid or trifluoroacetic acid that was expected since the pyrrole moiety is less basic than pyrrolidine. In the oxidized polymer, the pair of unshared electrons on the nitrogen atom are contributing to the pyrrole ring aromaticity, therefore, unavailable for protonation as in the case of polymer (VII). A comparison of the solubilities is given in Table I. 

This procedure provides a method for functionalizing the pyrrole ring 1n the 3-pos1t1on, normally a difficult synthetic step when conventional electrophilic substitution is used. The technique has been extended to addition of several aldehydes and acetone and to a number of pyrroles.4 The generality Includes photoaddition to imidazoles which are substituted in the 4-posltion. Pyrrole photoadduct alcohols are readily dehydrated to 3-alkenylpyrroles or oxidized to 3-acyl derivatives. 

PPy s have been integrated into other structures by polymerizing in the presence of a dissolved polymer. For example,46 polymerization of pyrrole has been achieved in a solution of polycarbonate dissolved in CHC13 with FeCl3 as oxidant. The composite was then precipitated using a nonsolvent such as methanol, ethanol, or acetone. The resultant structure was polycarbonate with conducting PPy dispersed throughout the matrix. 

In chlorophyll where Mg is the central atom it is oxidation of the porphoryn ring which occurs. Under mild oxidation conditions (e g. KMn04 and acetone the vinyl group of chlorophyll a and b is oxidised to carboxyhc acid substituents. Under strong oxidising conditions such as chromic acid a mixture of pyrroles results (Wong, 1989). 

A microemulsion polymerization method [62,63] was also reported to produce magnetic polypyrrole nanocomposites filled with 7-Fc203. The nanoparticles were dispersed in the oil phase. FeCla was used as an oxidizing agent. Sodium dodecylbenzenesulfonic acid (SDBA) and butanol were used as the surfactant and cosurfactant, respectively. FeCl3 (0.97 g) was dissolved in a mixture of 15 mol deionized water, SDBA (6 g), and butanol (1.6 ml). A specific amount of 7-Fc203 suspended nanoparticle solution was added to the above solution for dispersion. Pyrrole was added for nanocomposite polymer fabrication in the microemulsion system. The polymerization was continued for 24 hours and quenched by acetone. 

Soluble PPy can be polymerized by a relatively simple chemical oxidation procedure [27,67] beginning with the dissolution of 0.30 mol (20 g) of pyrrole and 0.15 mol (48 g) of DBSA in 400 mL of distilled water with vigorous stirring, forming a milky monomer emulsion. Various amounts of APS as an oxidant dissolved in distilled water were slowly added to the monomer solution. Polymerization was performed for various durations at various temperatures and then terminated by pouring excess methanol. The resultant PPy powder was filtered and washed sequentially with distilled water, methanol, and acetone several times, followed by drying in vacuum at room temperature for 12 h. 

Pyrrole is dried with CaH2 for 24 h, followed by distillation under reduced pressure. Ammonium persulfate is used as an oxidant and dodecylbenzene sulfonate as the codopant. 0.15 mol of dodecylbenzene sulfonic acid and 0.3 mol of pyrrole are dissolved in 500 mL of distilled water with vigorous stirring. 0.06 mol of ammonium persulfate in 100 mL of distilled water are slowly added to the above solution whose temperature is maintained at 0 °C. The reaction is carried out for 40 h and terminated by pouring methanol. The resultant PPy powder is filtered and washed sequentially with distilled water, methanol and acetone several times, followed by filtering and drying in a vacuum oven at 25 °C for 12h. The apparent polymerization yield is 42%. This PPy can be dissolved by soni-cation into m-cresol in reasonable amounts. Another report describes the use of sodimn di(2-ethylhexyl)sulfosuccinate in analogous conditions. 

Open circles show the conductivity of prepared Poly(pyrrole) when the oxidation potential of the solutions was controlled by changing solvents. When the oxidation potential of methanol solutions was controlled by adding FeCl2 at the initial stage, the conductivity of the prepared Poly(pyrrole) is shown by the filled circles. (1) DMA, (2) DMP, (3) Ethylene Glycol, (4) Me-OH, (5) Et-OH, (6) Water, (7) Pentanol, (8) Octyl Alcohol, (9) 0.7M Fe(C104)3, (10) Benzene, (11) Acetone, (12) Acetonitrile, and (13) Chloroform. After Reference [80], reproduced with permission. 

Poly (vinylchloride)-polypyrrole composite film was prepared by allowing the oxidative polymerization to take place in PVC matrix with diffused pyrrole. The PVC film was immersed in a swelling solution containing pyrrole so that the pyrrole monomer could diffuse into the polymer matrix and then subsequently polymerized in an oxidative solutions containing oxidant in an binary solvent system of similar solubility coefficients with PVC film. Mixture of acetone, n-hexane and pyrrole was chosen as a diffusion solution because it yields highly conductive and transparent composite film with good processability. 

After the immersion of the PVC film into the difusion solution the oxidative polymerization of pyrrole takes place in a 1.0 mole FeCls solution of binary solvent system with acecionitrile and methanol. The oxidation solution requires the capability of swelling PVC for pormoting the deeper penetration of the oxidant into the polymer matrix. For the mixture of acetonitrile and methanol with 1.0 mole FeCls oxidant, the mole fraction of acetonitrile determines the compatibility with the swollen PVC as well as the level of the oxidation potential. The mole ratio of 85/15 of acetonitrile/methanol resulted high electrical conductivity of the composite film with the solvent system of n-hexane, acetone, and pyrrole when polymerized at 0°C. The oxidation potential also varies with the amount of oxidant(FeCl3) as well as the reaction temperature. 

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