Electrogenerated bases application

Application of Electrogenerated Bases to Fluoro Organic Synthesis... 

APPLICATION OF ELECTROGENERATED BASES TO FLUORO-ORCANIC SYNTHESIS... 

Electrogenerated chemiluminescence (ECL) has proved to be useful for analytical applications including organic analysis, ECL-based immunosensors, DNA probe assays, and enzymatic biosensors. In the last few years, the electrochemistry and ECL of compound semiconductor nanocrystallites have attracted much attention due to their potential applications in analytical chemistry (ECL sensors). 

Advances have been achieved in recent years, such as the use of CL reagents as labels to derivatize and sensitively determine analytes containing amine, carboxyl, hydroxy, thiol, and other functional groups and their application in HPLC and CE [35, 36], the synthesis and application of new acridinium esters [37], the development of enhanced CL detection of horseradish peroxidase (HRP) labels [38], the use of immobilization techniques for developing CL-based sensors [39-42], some developments of luminol-based CL in relation to its application to time-resolved or solid-surface analysis [43], and the analytical application of electrogenerated CL (ECL) [44-47], among others. 

One of the earliest applications of digital simulation to inorganic chemistry was for analysis of isomerization of CpCo(l,3-CgH8) to CpCo(l,5-C8Hg), which proceeds via a simple square scheme (Figure 3). Because the 1,3 and 1,5 isomers have different E1/2 values (-2.27 V and -2.51V, respectively), resolution of the two species in voltammetric curves is possible. Variation of the scan rate produces different currents for the electrogenerated species based on... 

The most traditional approach for the electrodeposition of metal oxides and hydroxides is based on the cathodic electrogeneration of base [6]. Depending upon the deposition potential, choice of the anion and the pH of the solution, various reactions take place at the cathode, such as the reduction of nitrate ions in aqueous solutions. These reduction reactions cause a local pH increase in vicinity of the cathode either by the consumption of protons or by the generation of hydroxide ions as in the case of nitrate reduction, which subsequently leads to the precipitation of metal hydroxides. The best known application of this technique is the synthesis of nickel hydroxide by the electroreduction of aqueous nickel nitrate solutions. Depending on the metal and deposition conditions, this cathodic technique often yields hydroxides rather than oxides, making a post-deposition calcination for the transformation of the hydroxide to the oxide necessary. Unfortunately, the deposited amorphous hydroxides are often metastable. Other cathodic electrodeposition methods involve the direct reduction of the oxidation state of the metal cation and deposition of the oxide onto the electrode [9]. 

Electropolymerization of a functionalized precursor represents a straightforward method for the realization of modified electrodes endowed with specific electrochemical or optical properties. Electrode materials based on electrogenerated functional conjugated polymers and their application as electrochemical sensors have been already reviewed [162-165]. On the other hand, the sensitivity of the optical properties of ir-conjugated polymers to conformational changes has led to the realization of colorimetric sensors for the detection of various analytes extending from alkali metal ions to anions and biomolecules [165-168]. In general, the realization of sensors based on functional PTs relies on the fact that complexation at a side chain may lead to perturbation of the polymer conformation, which can be read by either electrochemical or optical methods. 

Some work has been done with fiber-optic-based chemiluminescence sensors. Luminol has been used with various enzymes immobilized on the end of an optical fiber. Sensors based on electrogenerated chemiluminescence with luminol or tris(2,2 -bipyridyl)ruthenium(II) have appeared the latter is particularly attractive due the regenerable nature of the reagent. Importantly, for these applications of liquid-phase chemiluminescence, the reactions are occurring at a reactive surface rather than in a homogeneous solution and as such mass transfer probably controls the overall response. 

Suzuki S, Kato M, Nakajima S (1994) Application of electrogenerated triphenylmethyl anion as a base for alkylation of arylacetic ester and arylacetonitriles and isomerization of allylbenzenes. Can J Chem 72 357-361... 

Chronopotentiometric analytical methods have also found application in the field of food analysis. In this technique, the oxidation or reduction of species at a constant current is carried out, and the transition time is measured as the quantitative characteristic [29]. In this context, recent chronopotentiometric methods have been reported for histamine determination in foodstuffs. One of these methods was based on the oxidation of the amine at a planar gold disc electrode in the presence of electrogenerated chlorine which facilitates charge transfer between the analyte and the electrode surface. Well-defined signals were observed at +1.15 V in hydrochloric acid medium, giving rise to a linear calibration plot in the 2- 1(X) mg/1 concentration range with an LOD of 0.27 mg/1 histamine. The method was applied to the determination of histamine in fermented sausages [30]. The same authors used a mercury film electrode to develop a chronopotentiometric method for histamine in cheese [29]. 

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