Biphase ordering

Condon NG, Leibsle FM, Parker T, Lennie AR, Vaughan DJ, Thornton G (1997) Biphase ordering on... 

Figure 15.15 STM image (20 x 20 nm ) of the surface of Fe Oj(0001) showing biphase ordering of coexisting FeO (a) and FCjOj (fS) phases from Condon. 1995 [61].

The results obtained in the biphasic hydroformylation of 1-octene are presented in Table 5.2-1. In order to evaluate the properties of the ionic diphosphine ligand... 

A clean first-order process may erroneously appear to be a biphasic one, and vice versa. If the distortion to the property-time curve is not so evident as in the example, there might be a smooth rise or fall from reactant to product. The linearity of the plot of In (Y, - Kcc) versus time depends on the end point reading Yr.. One must be cautious, however, in ascribing a mildly curved plot of In Y, - W) versus time to a biphasic pattern. Were the observed value of Yx off by a small amount, a simple adjustment could give a straight-line plot indicative of first-order kinetics. Of course, if Tec is adjusted to force linearity, one must surely ask whether the revised value of Yx represents a reasonable extrapolation of the data, lest the proper but more complex reaction pattern be concealed. 

In the framework of the mobile order and disorder (MOD) theory five components contribute most to the Gibbs free energy of partitioning of a solute in a biphasic system of two essentially immiscible solvents [23] ... 

The kinetics of the reaction is first order in both nitrile complex and azide.909 NaN3 reacts with [Co(tetren)(NCMe)]3+ at pH 5.7 to give the 5-methyltetrazolato complex [Co(tetren)(N4CMe)]2+. The reaction is biphasic, involving the initial rapid formation of the AM-bonded tetrazole followed by the slow linkage isomerization to the N2-bonded complex.907... 

CG Varelas, DG Dixon, CA Steiner. Zero-order release from biphasic polymer hydrogels. J Controlled Release 34 185-192, 1995. 

A heterogeneous olefin epoxidation catalyst containing both V and Ti in the active site was prepared by sequential non-hydrolytic grafting. The silica was exposed first to VO(OiPr)3 vapor followed by Ti(0 Pr)4 vapor. Formation of propene is evidence for the creation of Ti-O-V linkages on the surface. Upon metathesis of the 2-propoxide ligands with BuOOH, the catalyst becomes active for the gas phase epoxidation of cyclohexene. The kinetics of epoxidation are biphasic, indicating the presence of two reactive sites whose activity differs by approximately one order of magnitude. 

Finally, degradation processes which are usually assumed to be first order are not. Degradation in soil has been shown by Hamaker (27) to often behave in a biphasic manner. Biodegradation in water has been shown to more closely follow second order kinet-ics(28). Photolysis in solution is highly dependent on antenua-tion of light in the water body which will depend on water quality... 

Apart from these recycling aspects, liquid-liquid biphasic catalysis can also help to improve the selectivity of a given reaction. Attractive options arise from the preferential solubility of only one reactant in the catalyst solvent or from the in-situ extraction of desired reaction products out of the catalyst layer in order to avoid unfavourable consecutive reactions (see Figure 7.4) [36]. 

In the meantime temperature-dependent stopped-flow measurements were conducted on the latter complex in order to determine the activation parameters of the N-N cleavage reaction (24). Plots of the absorption intensity at 418 nm vs. time at T — —35 to +15°C indicate biphasic kinetics with two rate constants 0bs(p and obs(2)> in analogy to our measurements of the tungsten complex. This time, however, both rates depended upon the acid concentration. Interestingly much smaller rate constants 0bs(i) and 0bs(2)> were found for all acid concentrations than given by Henderson et al. for his (single) rate constant kobs (up to 1 order of magnitude). Furthermore plots of 0bs(i) and kohs(2) vs. the acid concentration showed no saturation behavior but linear dependencies with slopes k and k and intercepts k und k, respectively (s — acid dependent and i — acid independent), Eq. (2) ... 

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