Chemiluminescence decay

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

Figure 13, indicates that the first mole of phenol is released in <30 s, the same elapsed time for the chemiluminescence to reach a maximum intensity. In fact, the measured rate constant r, for the rise in the chemiluminescence emission, is identical to the rate of the first phenol s release from the oxalate ester. Furthermore, the slower rate of release of the second phenol ligand has a rate constant that is identical to the chemiluminescence decay rate f. Thus, the model allows a quantitative analysis of the reaction mechanism, heretofore not available to us. We intend to continue this avenue of investigation in order to optimize the chemiluminescence efficiencies under HPLC conditions and to delineate further the mechanism for peroxy-oxalate chemiluminescence. 

A peculiar effect was observed in the decomposition of 19 a with anthracene as fluorescer when oxygen was carefully removed from the solutions an increase of the chemiluminescence decay rate and of the dioxetane cleavage resulted. It was suggested that this was due to a catalytic effect of triplet anthracene (formed by energy transfer from triplet formate) on the decomposition of the dioxetane. When oxygen is present, triplet anthracene is quenched. Whether such a catalytic effect of triplet anthracene or similar compounds on dioxetane cleavage actually exists has not yet been fully established positive effects were observed by M. M. Rauhut and coworkers 24> in oxalate chemiluminescence and by S. Mazur and C. S. Foote 80> in the chemiluminescent decomposition of tetramethoxy-dioxetane, where zinc tetraphenylporphy-rin seems to exert a catalytic effect. However, the decomposition of trimethyl dioxetane exhibits no fluorescer catalysis 78h... 

R. Bezman and L. R. Faulkner 189> developed methods for defining a concise set of parameters which quantitatively describe the efficiencies of chemiluminescent electron-transfer reactions (see Section VIII. A.) by means of analysis of chemiluminescence decay curves. 

When oxygen is removed from a reaction solution of tetrakis-(dimethylamino)ethylene (TMAE), the chemiluminescence decays slowly enough to permit rate studies. The decay rate constant is pseudo-first-order and depends upon TMAE and 1-octanol concentrations. The kinetics of decay fit the mechanism proposed earlier for the steady-state reaction. The elementary rate constant for the dimerization of TMAE with TMAE2+ is obtained. This dimerization catalyzes the decomposition of the autoxidation intermediate. 

For the experimental determination of the 0, it is necessary to quantify the light output of the direct chemiluminescent process. The experimental definition of the direct chemiluminescence quantum yield is given in Eq. 36, that is, the initial rate of photon production (/q ) per initial rate of dioxetane decomposition k )[D]o). Alternatively, the total or integrated light intensity per total dioxetane decomposed can be used. The /t )[Z)]o term is readily assessed by following the kinetics of the chemiluminescence decay, which is usually first order. Thus, from a semilogarithmic plot of the emission intensity vs. time, the dioxetane decomposition rate constant kjj is obtained and the initial dioxetane concentration [Z)]o is known,especially if the dioxetanes have been isolated and purified. In those cases in which the dioxetanes are too labile for isolation and purification, [/)]o is determined by quantitative spectroscopic measurements or iodometric titration. 

The experimental procedure to determine 4>wa is quite analogous to that discussed for The experimental definition is given by Eq. 38, in which all the terms have been already defined. Again the dioxetane decomposition rate constant kj) is determined by following the first-order kinetics of the DPA-enhanced chemiluminescence decay. The initial or total DPA fluorescence intensity is standardized with a suitable light standard, usually with luminol or the scintillation cocktail. The photomultiplier tube should be corrected for wavelength response. ... 

Consequently, phospha-l,2-dioxetanes are the only reasonable intermediates that produce the excited carbonyl fragments and simultaneously satisfy the experimental results in the present study. In this study, the substituent effect on the ring closure step in the oxy-Wittig type reaction was revealed by chemiluminescence decay. The promotion of the ring formation results in the... 

A kinetics study has been performed on the aqueous iodine oxidation of the thiolactam (78). The rate of oxidation of (78) was found to be approximately 100 times that of a simple cyclic thioether, and this enhancement was ascribed to transannular anchimeric assistance provided by the nitrogen of the amide group <87JOC258i>. The thermal decomposition of the fused dioxetane (79) has been monitored by chemiluminescence decay, and this has been shown to follow first-order kinetics. The activation parameters have been calculated <83CL431>. Second-order rate constants for the quatemization of octahydro-lfl-azonine (9) and other azacycloalkanes with iodomethane in acetonitrile and methanol have been measured <68CCC1429>. The kinetics of the hydrogen-deuterium... 

It has been observed that liquid scintillators containing p-dioxane or Triton X-100 show chemiluminescence in the presence of a quaternary ammonium base such as Hyamine. This chemiluminescence decays gradually over a long period of time and is probably related to the singlet oxygen ( Ag) generated in situ (Peng, 1976). 

FIGURE 7B. XeF chemiluminescence decay from premixed XeP2/HN3 mixtures. The photolysis source was a KrF laser, whose 5 eV photon energy is insufficient to produce XeF from XeP2 by a one photon process. The time dependence of the XeF emission shows a many microsecond fluorescence pulse that clearly is due to azide/nitrogen chemistry (see Fig. 7b). 

Figure 8. Observed decay curves for TCP0-H202"DPA chemiluminescence. TEA, triethylamine a.u., arbitrary units. (Reproduced from Ref. 24.Copyright 1986 American Chemical Society.)...

This model permits a determination of the rate constants for the rise of the chemiluminescence intensity and its subsequent decay and, more importantly, allows a quantitative assessment of the effects of reaction conditions, such as solvent variation, temperature, or additives, on the rates (r and f), the time required (t... 

Recently, we have shown that non-isothermal chemiluminescence measurements for oxidized cellulose provide the same rate constants of cellulose degradation as may be measured from experiments on the decay of polymerization degree determined by viscometry. This may be also taken as indirect evidence that the light emission is somehow linked with the scission of polymer chains [29]. 

Provided that chemiluminescence intensity Iql is proportional to the rate of peroxyl radicals termination, that is Icl [PO ]2, which is often assumed in the literature, chemiluminescence intensity should achieve some quasi-stationary level when hydroperoxide concentration becomes stationary and its decay should correspond to consumption of oxidizable groups, PH, in a polymer. At the same time, the chemiluminometric curves of type (a), which are typical with an autoaccelerating increase of the light emission (Figure 4) are relevant for... 

Stopped-flow experiments of luminol chemiluminescence in the system luminol/pure DMSO/tert.butylate/oxygen 109> with independent variations of the concentrations of reactants confirmed the results obtained previously by E. H. White and coworkers 117> as to pseudo-first-order dependence of the chemiluminescence intensity upon each of the reactants. Moreover, the shapes of the decay curves obtained... 

CL reactions are commonly divided into two classes. In the type I (direct) reaction the oxidant and reductant interact with rate constant kr to directly form the excited product whose excited singlet state decays with the first (or pseudofirst)-order rate constant ks = kf+ kd. In the type II (indirect) reaction the oxidant and reactant interact with the formation of an initially excited product (kr) followed by the formation of an excited secondary product, either by subsequent chemical reaction or by energy transfer, with rate constant kA. The secondary product then decays from the lowest excited singlet state with rate constant kt. Type II reactions are generally denoted as complex or sensitized chemiluminescence. 

CL emissions can be characterized by four parameters, including color, intensity, rate of production, and decay of intensity. The properties of several organic, chemiluminescent reactions known to produce emissions of light are shown in Table 1. 

Chemiluminescence (CL) is the light emission produced by a chemical reaction in which chemically excited molecules decay to the ground state and emit photons. 

AMPPD is the best chemiluminescent substrate for detecting an ALP-labeled probe [2, 3], The enhanced sensitivity of the chemiluminescence based on the reaction of AMPPD with ALP depends on the enzymatic reaction time (Fig. 2), because the slow kinetics of the signal decay result in the accumulation... 

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