Reactions with indicators

Peroxymonosulphuric acid (PMSA, H SO ) proved to be a promising oxidizer in reactions with chemiluminescent substances (luminol) with participation of such ions as Mn(II), Cu(II), Ni(II), Cr(IV), V(V). The literature data show the possibility of utilization PMSA in indicating reaction with ferroin ([Fe(l,10-phenanthrolyne) ] ) which is accelerated by Mn(II) compounds. 

Organic derivatives fall into 4 classes RP0(0H)2, HP0(0R)2, R P0(0R)2 and the phosphite esters R(OR)3 this latter class has no purely inorganic analogues, though it is, of course, closely related to PCI3. Some preparative routes have already been indicated. Reactions with alcohols depend on conditions ... 

P 60] The observation of the flow patterns was performed using a microscope with a video camera [151]. Flow feed was achieved by hydrostatic pressure. A pH-indicator reaction with bromothymol blue and sodium hydroxide solution was applied, resulting in a dark blue color. Experiments were performed at flow rates of 50, 900 and 4000 pi min-1 for the mini channels and 60 and 6000 pi min4 for the micro channels. 

Enzymatic reactions that cannot be monitored directly by spectroscopic changes can be coupled to other reactions that do show such changes. One of the classic examples is the detection of glucose by an assay which depends on its conversion by hexo-kinase into glucose 6-phosphate, which is then coupled to an ancillary indicator reaction with NADP+ and glucose 6-phosphate dehydrogenase ... 

Figure 9.9 Calculated translational PEDs for the two indicated reactions with the OTS/PST Equation (9.60). The reactants are assumed to be prepared rotationally cold so that the total 1 = 0. The much larger centrifugal potential for the H atom loss reactions, results in the depletion of low translational energies.

Table 2 Indicator reactions with H2O2 as oxidant...

Lower case letters are used for elements to indicate reaction with one ligand. This simplifies the equation especially when all the ligands attached to the metal are not known (see Dessy, 1963). 

The cloud of gas-phase ions moving toward the mass analyzer is a very dilute matrix while ions of the same charge are unlikely to react with each other. So, unless the generated ions undergo in-source or post-source decay, or are purposefully reacted with gas molecules/ions or irradiated, they can make their way to the detector. To estimate or confirm the duration of incubation in ultra-fast mixing approaches, one often utilizes indicator reactions with well-characterized kinetics, such as the reaction of 2,6-dichloro-phenolindophenol and ascorbic acid (e.g., [98, 101]). 

As seen in the preceding section, the discoloration of degraded poly(vinyl chloride) is due to the formation of polyene sequences. Some stabilizers are capable of restoring the original colour of the polymer, indicating reaction with the polyenes present. For example, dibutyltin maleate undergoes a Diels-Alder reaction with polyenes [15]. Thus the sequence of conjugated double bonds is shortened. 

Figure B2.3.5. Typical time-of-flight spectra of DF products from the F + D2 reaction [28]- The collision energies and in-plane and out-of-plane laboratory scattered angles are given in each panel. The DF product vibrational quantum number associated with each peak is indicated. Reprinted with pennission from Faiibel etal [28]. Copyright 1997 American Chemical Society.

The Turing mechanism requires that the diffusion coefficients of the activator and inlribitor be sufficiently different but the diffusion coefficients of small molecules in solution differ very little. The chemical Turing patterns seen in the CIMA reaction used starch as an indicator for iodine. The starch indicator complexes with iodide which is the activator species in the reaction. As a result, the complexing reaction with the immobilized starch molecules must be accounted for in the mechanism and leads to the possibility of Turing pattern fonnation even if the diffusion coefficients of the activator and inlribitor species are the same 62. 

The desired pyridylamine was obtained in 69 % overall yield by monomethylation of 2-(aminomethyl)pyridine following a literature procedure (Scheme 4.14). First amine 4.48 was converted into formamide 4.49, through reaction with the in situ prepared mixed anhydride of acetic acid and formic acid. Reduction of 4.49 with borane dimethyl sulfide complex produced diamine 4.50. This compound could be used successfully in the Mannich reaction with 4.39, affording crude 4.51 in 92 % yield (Scheme 4.15). Analogous to 4.44, 4.51 also coordinates to copper(II) in water, as indicated by a shift of the UV-absorption maximum from 296 nm to 308 nm. 

The thermal decomposition of thia2ol-2-yl-carbonyl peroxide in benzene, bromobenzene, or cumene affords thiazole together with good yields of 2-arylthiazoles but negligible amounts of esters. Thiazol-4-ylcarbonyl peroxide gives fair yields of 4-arylthiazoles, but the phenyl ester is also a major product in benzene, indicating reactions of both thiazol-4-yl radicals and thiazol-4-carbonyloxy radicals. Thiazole-5-carbonyl peroxide gives... 

Choose which member in each of the following pairs reacts faster or has the more favor able equihbnum constant for reaction with the indicated reagent Explain your reasoning... 

End Point Determination Adding a mediator solves the problem of maintaining 100% current efficiency, but does not solve the problem of determining when the analyte s electrolysis is complete. Using the same example, once all the Fe + has been oxidized current continues to flow as a result of the oxidation of Ce + and, eventually, the oxidation of 1T20. What is needed is a means of indicating when the oxidation of Fe + is complete. In this respect it is convenient to treat a controlled-current coulometric analysis as if electrolysis of the analyte occurs only as a result of its reaction with the mediator. A reaction between an analyte and a mediator, such as that shown in reaction 11.31, is identical to that encountered in a redox titration. Thus, the same end points that are used in redox titrimetry (see Chapter 9), such as visual indicators, and potentiometric and conductometric measurements, may be used to signal the end point of a controlled-current coulometric analysis. For example, ferroin may be used to provide a visual end point for the Ce -mediated coulometric analysis for Fe +. 

Cyclohexane, produced from the partial hydrogenation of benzene [71-43-2] also can be used as the feedstock for A manufacture. Such a process involves selective hydrogenation of benzene to cyclohexene, separation of the cyclohexene from unreacted benzene and cyclohexane (produced from over-hydrogenation of the benzene), and hydration of the cyclohexane to A. Asahi has obtained numerous patents on such a process and is in the process of commercialization (85,86). Indicated reaction conditions for the partial hydrogenation are 100—200°C and 1—10 kPa (0.1—1.5 psi) with a Ru or zinc-promoted Ru catalyst (87—90). The hydration reaction uses zeotites as catalyst in a two-phase system. Cyclohexene diffuses into an aqueous phase containing the zeotites and there is hydrated to A. The A then is extracted back into the organic phase. Reaction temperature is 90—150°C and reactor residence time is 30 min (91—94). 

Because they are weak acids or bases, the iadicators may affect the pH of the sample, especially ia the case of a poorly buffered solution. Variations in the ionic strength or solvent composition, or both, also can produce large uncertainties in pH measurements, presumably caused by changes in the equihbria of the indicator species. Specific chemical reactions also may occur between solutes in the sample and the indicator species to produce appreciable pH errors. Examples of such interferences include binding of the indicator forms by proteins and colloidal substances and direct reaction with sample components, eg, oxidising agents and heavy-metal ions. 

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

An inversion of these arguments indicates that release agents should exhibit several of the following features (/) act as a barrier to mechanical interlocking (2) prevent interdiffusion (J) exhibit poor adsorption and lack of reaction with at least one material at the interface (4) have low surface tension, resulting in poor wettabihty, ie, negative spreading coefficient, of the release substrate by the adhesive (5) low thermodynamic work of adhesion ... 

Sorbic acid is oxidized rapidly in the presence of molecular oxygen or peroxide compounds. The decomposition products indicate that the double bond farthest from the carboxyl group is oxidized (11). More complete oxidation leads to acetaldehyde, acetic acid, fumaraldehyde, fumaric acid, and polymeric products. Sorbic acid undergoes Diels-Alder reactions with many dienophiles and undergoes self-dimerization, which leads to eight possible isomeric Diels-Alder stmctures (12). 

Thermal Decomposition of GIO2. Chloiine dioxide decomposition in the gas phase is chaiacteiized by a slow induction period followed by a rapid autocatalytic phase that may be explosive if the initial concentration is above a partial pressure of 10.1 kPa (76 mm Hg) (27). Mechanistic investigations indicate that the intermediates formed include the unstable chlorine oxide, CI2O2. The presence of water vapor tends to extend the duration of the induction period, presumably by reaction with this intermediate. When water vapor concentration and temperature are both high, the decomposition of chlorine dioxide can proceed smoothly rather than explosively. Apparently under these conditions, all decomposition takes place in the induction period, and water vapor inhibits the autocatalytic phase altogether. The products of chlorine dioxide decomposition in the gas phase include chlorine, oxygen, HCl, HCIO, and HCIO. The ratios of products formed during decomposition depend on the concentration of water vapor and temperature (27). 

A good technical grade of carbon tetrachloride contains not more than the following amounts of impurities 1 ppm acidity as HCl, 1 ppm carbon disulfide if manufactured by carbon disulfide chlorination, 20 ppm bromine, 200 ppm water, and 150 ppm chloroform. The residue should not exceed 10 ppm on total evaporation. The product should give no acid reaction with bromophenol blue, and the starch iodine test should indicate the absence of free chlorine. 

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