可溶性聚苯并噻吩的电化学合成

聚噻吩及其衍生物具有良好的导电性 ,优越的电致变色及荧光特性 ,可望用于研制各种新型微电子器件[1,2 ] .因此 ,这类聚合物的合成与表征一直受到广泛关注[3] .噻吩类聚合物是一个庞大的家族 ,其中聚异苯并噻吩早就被合成出来[4 ,5] .三氟化硼乙醚溶液 (ＢＦＥＥ)是电聚合芳香族化合物 (如噻吩、苯等 )的一种优良电解质[6～ 10 ] .在这一介质中 ,单体的氧化聚合电位很低 ,得到的导电高分子膜具有优良的机械力学性能 .本文将报道苯并噻吩在纯ＢＦＥＥ或ＢＦＥＥ与浓硫酸形成的混合电解质中的电化学聚合反应 .用这一方法合成得到了能发出蓝色…     

Low potential electrochemical polymerization of diphenyl ether and characterization of its polymers

High‐quality poly(diphenyl ether) (PDPE) films with electrical conductivity of 4.4 × 10^?1 S cm^?1 were synthesized electrochemically by direct anodic oxidation of diphenyl ether (DPE) in boron trifluoride diethyl etherate (BFEE) containing 5% concentrated sulfuric acid (SA) (by volume). The oxidation potential onset of DPE in pure BFEE was measured to be only 1.37 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile + 0.1 mol L^?1 tetrabutylammonium tetrafluoroborate (1.98 V vs. SCE). The addition of SA to BFEE can further decrease the oxidation potential onset of the monomer to 1.18 V versus SCE in the mixed electrolyte of BFEE + 5% SA. PDPE films obtained from this medium showed good redox activity and stability even in concentrated SA. Dedoped PDPE films were partly soluble in the strong polar organic solvent dimethyl sulfoxide. Fluorescent spectral studies indicated that soluble PDPE was a good blue‐light emitter with a quantum yield of 0.30. Infrared spectroscopy and quantum chemistry calculations indicated that the electropolymerization of DPE occurred mainly at C₄ and C_4′. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5932–5941, 2007     

Electrosynthesis and Characterization of Poly(N‐(9‐fluorenylmethoxycarbony)‐glycine)

High‐quality poly(N‐(9‐fluorenylmethoxycarbony)‐glycine) (PFG), a new kind of soluble polyfluorene derivative, was successfully synthesized electrochemically by direct anodic oxidation of N‐(9‐fluorenylmethoxycarbony)‐glycine (FG) in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of FG in BFEE was only 0.6 V vs. Pt, which was much lower than that in acetonitrile +0.1 mol/L tetrabutylammonium tetra?uoroborate (TBATFB). PFG film obtained from BFEE showed good electrochemical activity and thermal stability. It indicates that BFEE is a better medium for the electrosynthesis of PFG film. PFG is highly soluble in common organic solvents, facilitating potential applications as a blue‐light‐emitting material. Fluorescent spectra revealed that PFG was a good blue‐light emitter. Results of FT‐IR and ¹H NMR spectra indicated the polymerization location of N‐(9‐fluorenylmethoxycarbony)‐glycine occurred mainly at C(2) and C(7) positions of the fluorine ring.     

Chemistry of sulfonyl isocyanates and sulfonyl isothiocyanates. X. Possible routes to substituted imidazolidinethiones and hexahydropyrimidinethiones

4-Toluenesulfonyl isocyanate (I) reacted with 2-aminoethanol and 3-amino-l-propanol to give 2:1 isocyanate/amino alcohol addition products. 1-Amino-2-propanol and I gave 1:1 and 2:1 adducts while 2-amino-2-methyl-l-propanol afforded only a 1:1 adduct. 4-Toluenesulfonyl isothio-cyanate (III) gave 1:1 adducts with 2-aminoethanol, l-amino-2-propanol and 3-amino-l-propanol, the first two of which were cyclized by concentrated sulfuric acid to 1-(4-toluenesulfonyl)-imidazoline-2-thiones and the third to 1-(4-toluenesulfonyl)hexahydropyrimidine-2-thione. A 1:2 adduct was obtained from III and 2-amino-2-methyl-l-propanol. Amino acids reacted with I and with 4-chlorobenzenesulfonyl isocyanate (II) to give N-(arylsulfonyl)-N¹-(carboxylic acid)-ureas. N-(4-Toluenesulfonyl)-N¹-(acetic acid)-urea (XVI) was converted to the methyl ester (XIX) by concentrated sulfuric acid and methanol and to water-soluble unrecoverable products by sulfuric acid alone. Glycine and III gave N-(4-toluenesulfonyl)-N¹-(acetic acid)-thiourea (XX) which was converted to the methyl ester (XXII) by concentrated sulfuric acid/methanol and to the cyclic 1-(4-toluenesulfonyl)imidazolin-5-one-2-thione (XXI) by sulfuric acid alone.     

Low potential electrosyntheses of free‐standing poly(dibenzofuran) films in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid

Free‐standing poly(dibenzofuran) (PDBF) films were synthesized electrochemically by direct anodic oxidation of dibenzofuran in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) containing certain amount of trifluoroacetic acid (TFA). The oxidation potential of dibenzofuran in pure BFEE was measured to be only 1.31 V versus saturated calomel electrode (SCE). This value was much lower than that determined in acetonitrile + 0.1 mol L^?1 TBATFB (2.14 V vs. SCE). The addition of TFA to BFEE can further decrease the oxidation potential of the monomer to 1.07 V versus SCE in the mixed electrolyte of BFEE + 30% TFA. PDBF films obtained from this medium showed good electrochemical behavior, good electrochromic properties, and good thermal stability with conductivity of 10⁰ S cm^?1. FTIR and ¹H NMR spectra showed that the polymer was grown mainly via the coupling of the monomer at C₍₃₎ C₍₁₀₎ or C₍₄₎ C₍₉₎ positions (Scheme 1). As‐formed PDBF films were partly soluble in tetrahydrofuran (THF) or chloroform. Fluorescent spectral studies indicated that either soluble or PDBF in solid state was a good blue light PDBF emitter. To the best of our knowledge, this is the first report that free‐standing PDBF films can be electrodeposited. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1125–1135, 2006     

Mechanism of the acid hydrolysis of aromatic o-carboxyamides and relative imides

The kinetics of N-phenylphthalamic acid and of N-phenylphthalimide hydrolysis in aqueous solutions of sulfuric acid has been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o-carboxyl group (N-phenylphthalamic acid). Attack of the nonprotonized amide bond by the hydroxonium ion is suggested to be the rate-limiting step.     

Adamantylation of 3-Nitro- and 3-Ethoxycarbonyl-1,2,4-triazolo[5,1-c]-1,2,4-triazin-4-ones

Reaction of 3-nitro- and 3-ethoxycarbonyl-1,2,4-triazolo[5,1-c]-1,2,4-triazin-4-ones with 1-adamantanol (or 1-adamantyl nitrate) in concentrated sulfuric acid or with 1-bromoadamantane in sulfolane affords N-adamantyl derivatives. The adamantylation of 3-nitro-1,4-dihydro-7H-1,2,4-triazolo[5,1-c]-1,2,4-triazin-4-one yields a mixture of N⁸- and N¹-isomers that undergo interconversion in concentrated sulfuric acid along intermolecular mechanism.     

Electrosynthesis of blue-light-emitting oligo(1-bromopyrene) with favorable solubility

Bromo-group-substituted oligopyrene films were electrochemically synthesized by direct anodic oxidation of 1-bromopyrene (BrP) in boron trifluoride diethyl etherate (BFEE). The oxidation potential of BrP was measured to be approximately 0.52 V (vs. Ag/AgCl), which was much lower than that detected in a neutral electrolyte such as acetonitrile (1.2 V vs. Ag/AgCl) and CH₂Cl₂ (1.25 V vs. Ag/AgCl). Oligo(1-bromopyrene) (OBrP) films showed good redox activity in both BFEE and concentrated sulfuric acid. Fourier transform infrared spectroscopy, ¹H NMR, and theoretical calculations showed that the electropolymerization of the BrP monomer mainly occurred at the C₍₃₎, C₍₆₎, and C₍₈₎ positions. As-formed OBrP was a typical blue light emitter with fluorescent quantum yields of 0.27, also emitted strong and bright blue photoluminescence at excitation of 365 nm UV light. Furthermore, the films were readily soluble in dimethyl sulfoxide, CH₂Cl₂, acetonitrile, and acetone. All these results indicate that the striking OBrP films have many potential applications in various fields, such as optoelectronic materials, DNA fluorescence probes, and electrochemical sensors.     

Ion radicals. XIII. Spectroscopic and cryoscopic characterization of ions and ion radicals from phenothiazine and N-methylphenothiazine in sulfuric acid solutions

The formation and interconversion of the N-methylphenothiazine cation radical and the N-methylphenothiazine dication from both N-methylphenothiazine and N-methylphenothiazine S-oxide in sulfuric acid solutions have been demonstrated with e.s.r. and absorption spectroscopy. Cryoscopic measurements have shown that in slightly aqueous sulfuric acid N-methylphenothiazine S-oxide is converted to the N-methylphenothiazine dication and, analogously, phenothiazine 5-oxide is converted to the protonated phenazathionium ion (the phenothiazine dication).     

Synthesis,photopolymerization, and adhesive properties of new bisphosphonic acid monomers for dental application

Four new monomers, 3‐(N‐methylacrylamido)propylidenebisphosphonic acid, 3‐(N‐propyl‐acrylamido)propylidenebisphosphonic acid, 3‐(N‐hexylacrylamido)propylidenebisphosphonic acid, and 3‐(N‐octylacrylamido)propylidenebisphosphonic acid, have been synthesized in good yields and fully characterized by ¹H, ¹³C, ³¹P NMR, and HRMS. The copolymerization of these monomers with N,N′‐diethyl‐1,3‐bis(acrylamido)propane (DEBAAP) has been investigated with differential scanning calorimetry. These mixtures show a higher reactivity than DEBAAP. New self‐etch dental primers, based on these acrylamide monomers, have been formulated. Dentin shear bond strength measurements have shown that primers based on these bisphosphonic acids assure a strong bond between the tooth substance and a dental composite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5258–5271, 2009     

On the Beckmann rearrangement of ketoximes: A kinetic study in trifluoromethanesulfonic acid

The formation and the destruction of an intermediate involved in the Beckmann rearrangement of 2,4,6‐trimethylacetophenone oxime have been studied in concentrated trifluoromethanesulfonic acid by kinetic and spectroscopic measurements. Observed (k_obs) and thermodynamic rate constants (k^o) have been estimated and the values compared with the ones obtained in perchloric, sulfuric, and methanesulfonic acids. In the range 80–100 wt% of sulfuric acid, combined analysis of k_obs and k^o rates shows a specific catalysis due to [H₂SO₄] species. In trifluoromethanesulfonic acid, lower rate constants, compared to the values in sulfuric acid, have been observed which differ at 99 wt% by a factor of 10³ ca. The catalytic effect of different strong acids, the structure of the intermediate inferred from Raman and NMR spectra, and the role of the ion‐pairs involved in the reaction are discussed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 417–426, 2004     

Electrosyntheses of high‐quality polyphenanthrene in the electrolyte of boron trifluoride diethyl etherate containing trifluoroacetic acid

A novel inherently conducting polymer, high‐quality polyphenanthrene (PPh) films were synthesized electrochemically by direct anodic oxidation of phenanthrene (Ph) in boron trifluoride diethyl etherate (BFEE) containing a certain amount of trifluoroacetic acid (TFA). The oxidation potential of Ph in this medium was measured to be only 0.63 V versus SCE, which was greatly lower than that determined in acetonitrile + 0.1 mol L^?1 Bu₄NBF₄ (1.55 V vs. SCE). The electrolytes of BFEE containing TFA enable facile anodic oxidation of Ph monomer; however, similar oxidation using acetonitrile never produces such a polymeric material. PPh films obtained from this medium showed good redox activity and stability even in concentrated sulfuric acid. Dedoped PPh films were partly soluble in polar solvent such as CH₂Cl₂, acetone, tetrahydrofuran, and dimethyl sulfoxide. Fluorescent spectral studies indicate that PPh is a good blue‐light emitter. The structure and morphology of the polymer were studied by UV–vis spectroscopy, FTIR spectroscopy, ¹H NMR spectroscopy, and scanning electron microscopy, respectively. The results of quantum chemistry calculations of Ph monomer and the spectroscopies of dedoped PPh indicated the polymerization mainly occurred at C₍₉₎ and C₍₁₀₎ positions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3929–3940, 2007     

A reinvestigation of the bamberger-ham phenazine. Synthesis: A limitation

The Bamberger-Ham condensation of 4-substituted nitrosobenzenes in concentrated sulfuric acid reported as a method of synthesis for phenazine N-oxides has been found to be limited to electron donating substituents. Methyl 4-nitrosobenzoale has been found to react under these conditions to give dimethyl 2-nitrodiphenylamine-4, 5-diearboxylate ( 2 ). Compounds of unknown structure previously reported to arise from acid treatment of 4-bromo- and 4-chloronilrosobenzene have been shown to be 4, 5-dibromo-2-nitrosophenylamine ( 10 ) and the analogous dichloro compound. Treatment under stronger acidic conditions (oleum) converted 10 but not 2 into the corresponding phenazine N-oxide. Mechanistic implications are discussed.     

Mechanism of oxidation of cyclohexanehexol (inositol) by quinquevalent vanadium

The oxidation of inositol by quinquevalent vandadium in acid medium is a first-order reaction both in vanadium (V) and inositol. The stoichiometry of the reaction is consistent with the use of two equivalents of vanadium (V) per mole of inositol with the formation of one mole of inosose. The reaction is catalyzed both by sulfuric and perchloric acid, but the rate is faster in sulfuric acid than in perchloric acid. In 1M–6M perchloric acid solutions the reaction has shown a variable order in H⁺, but in solutions of 2M–5M sulfuric and perchloric acid of constant ionic strength, the rate has a linear dependence on [H⁺]². There is also a linear correlation between the rate and bisulfate ions in sulfuric acid at constant hydrogen ion concentration. The energy of activation is found to be 19 kcal/mole and a negative entropy value of ? 14 e.u. A suitable mechanism, consistent with the kinetics in 2M–5M acid solutions, is suggested and the values of various rate constants are evaluated.     

Synthesis,photopolymerization and adhesive properties of new hydrolytically stable phosphonic acids for dental applications

Novel monomers 2‐(N‐methylacrylamido)ethylphosphonic acid, 6‐(N‐methylacrylamido)hexylphosphonic acid, 10‐(N‐methylacrylamido)decylphosphonic acid, and 4‐(N‐methylacrylamidomethyl)benzylphosphonic acid have been prepared in good yields for use in dental adhesives. They have been fully characterized by ¹H‐NMR, ¹³C‐NMR, ³¹P ‐ NMR, and by HRMS. All monomers are hydrolytically stable in aqueous solution. Free radical homopolymerizations of these monomers have been carried out in solution of ethanol/water (2.5/1:v/v), using 2,2′‐azo(2‐methylpropionamidine) dihydrochloride (AMPAHC) as initiator. They lead to homopolymers in moderate to excellent yields. Structure of the polymers has been confirmed by SEC/MALLS and ¹H‐NMR spectra. The photopolymerization behavior of the synthesized monomers with N,N′‐diethyl‐1,3‐bis(acrylamido)propane has been investigated by DSC. New self‐etch primers, based on these acrylamide monomers, have been formulated. Dentin shear bond strength measurements have shown that primers based on (N‐methylacrylamido)alkylphosphonic acids assure a strong bond between the tooth substance and a dental composite. Moreover, the monomer with the longest spacer group provides the highest shear bond strength. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7074–7090, 2008     

Untersuchungen über aromatische Amino-Claisen-Umlagerungen

Investigations on Aromatic Amino-Claisen Rearrangements The thermal and acid catalysed rearrangement of p-substituted N-(1′,1′-dimethylallyl)anilines (p-substituent=H (5) , CH₃ (6) , iso-C₃H₇ (7) , Cl (8) , OCH₃ (9) , CN (10) ), of N-(1′,1′-dimethylallyl)-2,6-dimethylaniline (11) , of o-substituted N-(1′-methylallyl)anilines (o-substituent=H (12) , CH₃ (13) , t-C₄H₉ (14) , of (E)- and (Z)-N-(2′-butenyl)aniline ((E)- and (Z)- 16 ), of N-(3′-methyl-2′-butenylaniline (17) and of N-allyl- (1) and N-allyl-N-methylaniline (15) was investigated (cf. Scheme 3). The thermal transformations were normally conducted in 3-methyl-2-butanol (MBO), the acid catalysed rearrangements in 2N -0,1N sulfuric acid. - Thermal rearrangements. The N-(1′,1′-dimethylallyl)anilines rearrange in MBO at 200-260° with the exception of the p-cyano compound 10 in a clean reaction to give the corresponding 2-(3′-methyl-2′-butenyl)anilines 22–26 (Table 2 and 3). The amount of splitting into the anilines is <4% ( 10 gives ? 40% splitting). The secondary kinetic deuterium isotope effect (SKIDI) of the rearrangement of 5 and its 2′,3′,3′-d₃-isomer 5 amounts to 0.89±0.09 at 260° (Table 4). This indicates that the partial formation of the new s?-bond C(2), C(3′) occurs already in the transition state, as is known from other established [3,3]-sigmatropic rearrangements. The rearrangement of the N-(1′-methylallyl)anilines 12–14 in MBO takes place at 290–310° to give (E)/(Z)-mixtures of the corresponding 2-(2′-Butenyl)anilines ((E)- and (Z)- 30,-31 , and -32 ) besides the parent anilines (5–23%). Since a dependence is observed between the (E)/(Z)-ratio and the bulkiness of the o-substituent (H: (E)- 30 /(Z)- 30 =4,9; t-C₄H₉: (E)- 32 /(Z)- 32 =35.5; cf. Table 6), it can be concluded, that the thermal amino-Claisen rearrangement occurs preferentially via a chair-like transition state (Scheme 22). Methyl substitution at C(3′) in the allyl chain hinders the thermal amino-Claisen-rearrangement almost completely, since heating of (E)-and (Z)- 16 , in MBO at 335° leads to the formation of the expected 2-(1′-methyl-allyl) aniline (33) to an extent of only 12 and 5%, respectively (Scheme 9). The main reaction (?60%) represents the splitting into aniline. This is the only observable reaction in the case of 17 . The inversion of the allyl chain in 16 - (E)- and (Z)- 30 cannot be detected - indicated that 33 is also formed in a [3, 3]-sigmatropic process. This is also true for the thermal transformation of N-allyl- (1) and N-allyl-N-methylaniline (15) into 2 and 34 , respectively, since the thermal rearrangement of 2′, 3′, 3′-d₃- 1 yields 1′, 1′, 2′-d₃- 2 exclusively (Table 8). These reaction are accompanied to an appreciable extent by homolysis of the N, C (1′) bond: compound 1 yields up to 40% of aniline and 15 even 60% of N-methylaniline ((Scheme 10 and 11). The activation parameters were determined for the thermal rearrangements of 1, 5, 12 and 15 in MBO (Table 22). All rearrangements show little solvent dependence (Table 5, 7 and 9). The observed ΔH^≠ values are in the range of 34-40 kcal/mol and the ΔS^≠ values very between -13 to -19 e.u. These values are only compatible with a cyclic six-membered transition state of little polarity. - Acid catalysed rearrangements. - The rearrangement of the N-(1′, 1′-dimethylallyl) anilines 5-10 occurs in 2N sulfuric acid already at 50-70° to give te 2-(3′-methyl-2′-butenyl)anilines 22-27 accompanied by their hydrated forms, i.e. the 2-(3′-hydroxy-3′-methylbutyl) anilines 35-40 (Tables 10 and 11). The latter are no more present when the rearrangement is conducted in 0.1 N sulfuric acid, whilst the rate of rearrangement is practically the same as in 2 N sulfuric acid (Table 12). The acid catalysed rearrangements take place with almost no splitting. The SKIDI of the rearrangement of 5 and 2′, 3′, 3′-d₃- 5 is 0.84±0.08 (2 N H₂SO₄, 67, 5°, cf. Table 13) and thus in accordance with a [3,3]-sigmatropic process which occurs in the corresponding anilinium ions. Consequently, the rearrangement of a 1:1 mixture of 2′, 3′, 3′-d₃- 5 and 3, 5-d₂- 5 in 2 N sulfuric acid at 67, 5° occurs without the formation of cross-products (Scheme 13). In the acid catalysed rearrangement of the N-1′-methylallyl) anilines 12-14 at 105-125° in 2 N sulfuric acid the corresponding (E)- and (Z)-anilines are the only products formed (Table 14 and 15). Again no splitting is observed. Furthermore, a dependence of the observed (E)/(Z) ratio and the bulkiness of the o-substituent ( H : (E)/(Z)- 30 = 6.5; t- C ₄ H ₉: (E)- 32 /(Z)- 32 = 90; cf. Table 15) indicates that also in the ammonium-Claisen rearrangement a chair-like transition state is preferentially adopted. In contrast to the thermal rearrangement the acid catalysed transformation in 2 N-O, 1 N sulfuric acid (150-170°) of (E)- and (Z)- 16 as well as of 1 and 15 , occurs very cleanly to yield the corresponding 2-allylated anilines 33, 2 and 34 (Scheme 15 and 18). The amounts of the anilines formed by splitting are <2%. During longer reaction periods hydration of the allyl chain of the products occurs, and in the case of the rearrangement of (E)- and )Z)- 16 the indoline 45 is formed (Scheme 15 and 18). All transformations occur with inversion of the allyl chain. This holds also for the rearrangement of 1 , since 3′, 3′-d₂- 1 gives only 1′, 1′-d₂- 2 (Scheme 17). The activation parameters were determined for the acid catalysed rearrangement of 1, 5, 12 and 15 in 2 N sulfuric acid (Table 22). The ΔH^≠ values of 27-30 kcal-mol and the ΔS^≠ values of +9 to -12 e.u. are in agreement with a [3, 3]-sigmatropic process in the corresponding anilinium ions. The acceleration factors (k_H+/k_Δ) calculated from the activation parameters of the acid catalysed and thermal rearrangements of the anilines are in the order of 10⁵ - 10⁷. They demonstrate that the essential driving force of the ammonium-Claisen rearrangement is the ‘delocalisation of the positive charge’ in the transition state of these rearrangements (cf. Table 23). Solvation effects in the anilinium ions, which can be influenced sterically, also seem to play a role. This is impressively demonstrated by N-(1′, 1′-dimethylallyl)-2, 6-dimethylaniline (11) : its rearrangement into 4-(1′, 1′-dimethylallyl)-2, 6-dimethylaniline (43) cannot be achieved thermally, but occurs readily at 30° in 2 N sulfuric acid. From a preparative standpoint the acid catalysed rearrangement in 2 N-0, 1 N sulfuric acid of N-allylanilines into 2-allylanilines, or if the o-positions are occupied into 4-allylanilines, is without doubt a useful synthetic method (cf. also [17]).     

Oxidation of fluorenes by ammonium meta vanadate—a kinetic study

The oxidation of fluorene by vanadium(V) in aqueous acetic acid containing sulfuric acid (1.0M) at 50°C produces fluorenone and 2-hydroxy diphenyl 2′-carboxaldehyde. The order with respect to each reactant is found to be 1. The order dependence on sulfuric acid concentration is 4, indicating that V(OH)₂³⁺ could be the active species. An increase in the acetic acid percentage in the solvent medium increases the rate of the reaction. The effect of solvent variation has been discussed in the light of the acidity function and the polarity of the medium. The effect of substituents on the rate has been studied for seven substituted fluorenes, and a linear relationship exists between log k versus σ values with the slope ρ = -3.2. A small isotope effect is observed for the oxidation of the parent compound (k_H/k_D = 1.2). The effect of temperature on the rate of the reaction has been studied, and the activation parameters are discussed. A mechanism involving the rate-limiting formation of a cation-radical intermediate is proposed.     

Determination of Trace Iron(II) in the Presence of Iron(III)

The determination of trace iron(II) is usually interfered by the presence of iron(III) when ortho-phenanthroline colorimetric method is used. In this report a chromogenic reagent which contains ortho-phenanthroline-EDTA mixture has been developed to decrease the interference of ferric ion after adjusting the acidity of sample at 0.1 N by adding the sulfuric acid. The procedure is also simplified by introducing sulfamate buffer solution (pH= 1.5) without adjusting the acidity of sample with sulfuric acid. If iron(III) is not present in the sample, this method is also applicable. The comparative results are exhibited for the present method and the conventional o-phenanthroline method.     

Kinetics and Mechanism of the Electro-oxidation of Gold in Thiocarbamide Solutions

The kinetics and mechanism of the electrooxidation of gold and thiocarbamide in sulfuric acid solutions of thiocarbamide (TC) have been investigated. The potentials for the oxidation of gold in TC solutions to [Au(TC)₂]⁺ _ads and [Au(TC)₃]³⁺ _ads are 0.132 and 0.561 V (relative to the standard silver chloride electrode). The electrooxidation of thiocarbamide in sulfuric acid solution is characterized by two maximums on voltammograms at 0.983 V (formation of formamidine disulfide, FAD) and 1.437 V (oxidation of FAD, sulfides and hydrosulfides of gold(I)). The calculated rate constants for the electrosolution of gold at the maximum current of the voltammogram is k ₁ = 1.15·10^–5 cm/s and at the minimum current is k ₂ = 3.13·10^–6 cm/s in sulfuric solutions of TC. A mechanism is proposed for the electrosolution of gold and TC in sulfuric acid solutions of thiocarbamide.     

Direct electrosynthesis and characterization of a new soluble polyfluorene derivative containing carboxyl group in boron trifluoride diethyl etherate

High-quality poly(fluorene-9-acetic acid) (PFAA), a new soluble polyfluorene derivative, was synthesized electrochemically by direct anodic oxidation of fluorene-9-acetic acid (FAA) in boron trifluoride diethyl etherate (BFEE) containing a certain amount of trifluoroacetic acid (TFA). This electrolyte enables facile anodic oxidation of FAA monomer at lower potential (1.05 V vs. SCE). PFAA films with conductivity of 0.53 S cm⁻¹ obtained from this medium showed better redox activity and thermal stability in relation to unsoluble poly(fluorene-9-carboxylic acid). Fluorescent spectral studies indicate that PFAA film with high fluorescence quantum yields and photochemical stability is a good blue-light emitter. The structure and morphology of the polymer were studied by UV–vis, FT-IR, ¹H NMR spectra and scanning electron microscopy, respectively.