Kinetic similarity

Phosphonoformic acid (85) decarboxylated in acid solution, and it was proposed that the uncatalysed reaction involved a simple decarboxylation of the zwitterion. The acid-catalysed reaction showed some kinetic similarity to that of mesitoic acid and an elimination of carbon dioxide as trihydroxymethylcarbonium ion was preferred. Participation of the trans vicinal phosphonyl group in the solvolysis of the halides (86) and (87) has been deduced from rate measurements. In the norbornene derivatives, the relative rates of loss of chloride from (87a) and (87b) were 5 x 10 1. 

CO2 production is predominated by a mechanism which proceeds throuRh the same rate-determininR step as the epoxidatlon path. Thus exist the very strong kinetic similarities for EtO and CO2 production (2,3,6,25). The other path to CO2 is less understood ( ) and only predominates under extreme conditions, but is more sensitive to 6. ... 

Note that besides the kinetics of the change of electric conductivity (2.44) - (2.47) considered, the logarithmic kinetics similar to that of Zeldovich - Roginsky - Elovich is often observed in experiment (see Section 1.10) [30, 65, 82, 83] ... 

Sauna, Z. E., Ambudkar, S. V., Characterization of the catalytic cycle of ATP hydrolysis by human p-glycoprotein. The two ATP hydrolysis events in a single catalytic cycle are kinetically similar but affect different functional outcomes, J. Biol. Chem. 2001, 276, 11653-11661. 

Note It is essential to carefully examine the analytical data for the presence of cyclic compounds as a result of side reactions involved. The cyclization occurs as dendrimer amidation versus bridging amidation are kinetically similar. To prevent the intradendrimeric cyclization a large excess (50-fold) of 1,2-ethylenediamine is required. The excesses are removed to an undetectable level by azeotropic techniques. 

In kinetics, similar relationships apply, but the volume of activation AV can be determined only from the pressure dependence of the rate coefficient k, since the partial molal volumes V of transition states are not directly measurable. Conversely, however, equation 4 can yield values of V. ... 

We thought that the resumption of oxidation after a few min was likely due to the depletion of NO since subsequent additions of NO inhihited oxidation with kinetics similar to the first addition. In order to prove this, we repeated the experiment, hut this time determined the [ NO] at periodic time intervals. We initiated the experiment with 20 pM and then added 0.9 pM NO 1 min later. At this 1 min time point, oxidation was inhihited (Figure 3). This inhibition continued until about 4.5 min, which is about when the [ NO] fell to below the limit of detection. At this time there was still sufficient Fe (7.2 pM) to reinitiate oxidation. These results demonstrate that NO is acting as a chain-breaking antioxidant during cellular lipid peroxidation. 

This equation indicates that the reaction rate is proportional to the reaction affinity A near the equilibrimn (Alinear kinetics similar to Ohm s law in the electric current versus voltage relationship. 

In the bovine case, the oxidation of the enzyme in the presence of phosphate is slow like that observed for uteroferrin (k = 0.07 min ) however, the color change and loss of EPR also follow kinetics similar to the loss of enzyme actvity. 

The first reactions were carried out at room temperature in devices fabricated from a thiolene resin cured between two glass slides. 2-Hydroxypropyl methacrylate (HPMA) was polymerized by ATRP, and reaction kinetics similar to those obtained in a traditional batch reaction were obtained by adjusting the total flow rate of the fluid through the channel and treating the residence time in the channel as the reaction time (Fig. 21b,c) [102]. 

The electron- and hole-trapping dynamics in the case of WS2 are elucidated by electron-quenching studies, specifically by the comparison of polarized emission kinetics in the presence and absence of an adsorbed electron acceptor, 2,2 -bipyridine [68]. In the absence of an electron acceptor, WS exhibits emission decay kinetics similar to those observed in the M0S2 case. The polarized emission decays with 28-ps, 330-ps, and about 3-ns components. For carrier-quenching studies to resolve the dynamics of electron trapping, it is necessary that the electron acceptor quenches only conduction-band (not trapped) electrons. It is therefore first necessary to determine that electron transfer occurs only from the conduction band. The decay of the unpolarized emission (when both the electron and the hole are trapped) is unaffected by the presence of the 2,2 -bipyridine, indicating that electron transfer docs not take place from trap states in the WS2 case. Comparison of the polarized emission kinetics in the presence and absence of the electron acceptor indicates that electron transfer does occur from the conduction band. Specifically, this comparison reveals that the presence of 2,2 -bipyridine significantly shortens the slower decay component of the polarized... 

Note, however, that this thermodynamic condition alone is not sufficient to guarantee instability of the intermediates. One of the energy barriers may be so high that the faradaic potential region is shifted beyond the standard potential of the first electron transfer, i.e. the intermediate Y is stabilized kinetically. Similar reasoning applies to a non-linear mechanism. 

A method to derive kinetic similar to (2.3.37), (2.3.43) has certain shortcomings. Say, Waite [84, 94, 95] has neglected the undistinguishabil-ity of similar reactants and related symmetry of the probability densities wm,m ( r m> OOm l 0 with respect to the permutation of coordinates in r m (or Accordingly, his approach is often called asymmetric ... 

Based on the work done in our laboratory, we believe that multiple enzymes of the same type are derived from the same enzyme and potentially arise from partial proteolysis of such an enzyme (10). In previous studies, we have purified three distinct cellobiases from T. reesei which are chromatographically distinct yet kinetically similar. 

Linear copolymers of Gd(DTPA-bisamide) or Gd(EGTA-bisamide) units with poly(ethylene-glycol) (PEG) or polyalkyl (-(CH2)n- n = 6,10 and 12) spacers also had water exchange kinetics similar to that of the corresponding monomer chelate [60-62]. An 170 NMR study on the micellar system formed in aqueous solution of the amphiphilic DOTA-derivative [Gd(D0TA-C12)(H20)] also showed that the water exchange is not altered by the micellar structure [63]. 

These results explain the findings of Blackley and Haynes who also showed that the molecular weight of the polymer formed in the presence of ethyl benzene was lower than that in its absence. Calculation from their experimental data shows that their n varied from 0.005 to 0.039 radicals per particle, well into Case 1. Thus, their explanation on the basis of the Trommsdorff "gel" effect cannot be correct since this requires the mutual termination of two macroradicals in a particle, which obtains only under Case 3 kinetics. Similar experiments on the effect of the diluents on "insitu" (unseeded) and seeded emulsion polymerization indicates that n decreases due to desorption of free radicals from the particles (27). 

Discussion The kinetic similarity of the dichromate reduction in the presence of cupric acetate and the reduction of cupric acetate itself support the view that both have the same rate-controlling step. Halpern and co-workers suggested that the rate is determined by a bimolecular process involving one molecule of cupric acetate and one molecule of hydrogen. They have therefore, proposed the following reaction scheme. 

Although it is basically possible to apply the theory of similarity to chemical processes and to scale up one of these processes in such a way that geometric, fluid dynamic, thermal and reaction-kinetic similarity is retained to a greater or lesser extent, these transformation processes are only of limited importance. They may be quite useful for increasing equipment performance two to five-fold but hardly to much larger amounts. This circumstance is of importance since it is more or less equivalent to practical failure of the theory of similarity. This, however, was not to be expected from the beginning, especially in view of the fact that the theory of simila-... 

Thus the kinetics of the zeolite catalyzed reactions clearly paralleled closely those of the homogeneous reaction using the same transition metal as catalyst. Again zeolites acted as simple solvents for the carbonylation reaction though perhaps a specific role of the zeolite should not perhaps be entirely excluded. The kinetic similarities strongly suggested nearly identical reaction pathways in the zeolite medium and in solution with identical rate limiting step (24, 27). 

Lorazepam disinhibits aggression more than its chemically and kinetically similar analogue oxazepam (8). 

Lorazepam shares with other benzodiazepines the ability to impair explicit memory, but has a distinct further effect on implicit memory as well (10). However, it impairs memory more than its chemically and kinetically similar analogue, oxazepam (11). The effects of lorazepam 2.5 mg and diazepam 0.3 mg/kg on explicit and implicit memory tasks have been examined in 24 men and 24 women randomly allocated to lorazepam, diazepam, or placebo (10). An implicit word-stem completion task and explicit memory tasks of immediate and delayed word recall and word recognition were administered 90 minutes after drug administration. Both diazepam and lorazepam significantly impaired performance on explicit memory measures. Only lorazepam significantly impaired performance on the implicit memory task. 

If we included all possible intermediates BC and CA, then Eq. (XII.15.5) would consist of a sum of three kinetically similar terms. 

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