Isolated sorbate

Isolated inner-sphere surface complexation (ISC). Isolated sorbate cations or oxyanions (e.g., metalloids) bond separately to the surface by sharing one or several... 

This work was repeated by several groups7 11 in the reaction of sodium dimethyl-malonate with methyl sorbate, Farmer and Metha9 observed small amounts of the 1,4-adduct besides the 1,6-addition product. Difficulties in conducting the transformations and analyzing the products are evident from reports on malonate additions to ethyl muconate12-14 depending on the reaction conditions, the expected 1,4-adduct (equation 4) or isomerization products formed by double bond displacement were isolated. Nucleophilic 1,4- and 1,6-addition reactions to 2,4-pentadienenitrile were also reported15-17. 

Styrene, leads to [4 + 2]-adducts exclusively (251-258) 242 is also isolated in varying amounts, With methyl sorbate both [4 + 2]- and [4 + 4]-adducts (259-262) are obtained. 1,4-Dicarbomethoxybutadiene does not add to 138 242 is obtained in 90% yield. All photoadducts (251-262) are photolabile on irradiation (z — 253.7 nm) they are reconverted to 138 and the alkene. Significantly for preparative purposes, the product distributions (stereo-, regio-, and peri-selectivity) differ considerably from those obtained in the thermal Diels-Alder reactions (Section IV,B) mechanistic details are given in the original papers. 

To provide an estimate of constants, Ktex, suitable for use in Eq. 11-55, let us try to isolate the contribution of the sorbate s hydrophobicity using some available data. For the alkyl ammonium ions exchanging with sodium cations in the data of Cowan and White (1958), we have (see Eqs. 11-37 to 11-44) ... 

In fact sorbic acid (XXXIII) has been transformed in menthyl-sorbate and the ester (XXXIV) has been polymerized (36) by butyl-lithium (Scheme 6) the prevalence of asymmetric carbon atoms having one of the possible configurations in the main chain of the polysorbic acid (XXXV), not isolated by the authors, has been proved by oxidizing the polymer and measuring the optical activity of the obtained methyl succinic acid, which actually was optically active and had an optical purity of 6% (36). 

PAHs in soil may partition into soil organic matter (SOM) or adsorb on soil minerals. The sorptive properties of SOM fractions for organic contaminants in soil play an important role on the transportation of PAHs in soil. Xiao et al. (2004) has reported that soil/sediment organic matter can be fractionated into four fractions with a combined wet chemical procedure and that kerogen and black carbon (BC) are major SOM components in soil/sediment samples collected from the industrialized suburban areas of Guangzhou, China. Phenanthrene and naphthalene were used as the sorbates to study PAH s sorption isotherms on four original and four Soxhlet-extracted soil/sediment samples, 15 isolated SOM fractions, and a char as the sorbents. The sorption isotherms of phenanthrene and naphthalene on all the sorbents were variously nonlinear. The particulate kerogen and black carbon (KB) fractions... 

Table XIX shows the results of reactions of silyl ketene acetals derived from propionates with crotonate, cinnamate, sorbate, and fumarate in the presence of aluminum ion-exchanged montmorillonite (Al-Mont) (62). The reactions proceeded at low temperatures. The Michael products could be isolated in the unstable form of a trimethylsilyl ketene acetal in good yield owing to an easy work-up procedure (removal of the solid catalyst). It is noteworthy that the montmorillonite-induced Michael addition to a polyenoate occurred regioselectively in a 1,4-fashion in the case of methyl sorbate (Table XIX, Entry 4), the preference for 1,4-addition (98%) over 1,6-addition (2%) is notable because the addition of a lithium enolate (a conventional...

Reviews (9, 63, 64) of the reactions between hydroxylated mineral surfaces and aqueous solutions brought out the richness of variety found in surface phenomena involving natural particles. Isolated surface complexes, the principal topic of this chapter, are expected when reaction times are short and the adsorbate content is low [Figure 6, inspired by Schindler and Stumm 63)]. Thus, surface complexes occupy a reasonably well-defined domain in the tableau of reaction time scale versus sorbate concentration. Localized clusters of adsorbate (47, 48, 65, 66) that contain two or more adsorbate ions bonded together can form if the amount sorbed is increased by accretion or bv the direct adsorption of polymeric species (multinuclear surface complexes). Surface clusters can erase the hyperfine structure in the ESR spectrum of an immobilized adsorbate (33, 67) or produce new second-neighbor peaks from ions like the absorber in its EXAFS spectrum (47, 66). 

To demonstrate the organic acid activities at various pH values, a study done on the salts calcium propionate, sodium benzoate, and potassium sorbate is herewith discussed. These salts were found to be effective and to inhibit some isolates from bakery products at pH 4.5 when applied at concentration of 0.3%. In a sponge cake (an analogue of pH 6) addition of these same weak organic acids salts appeared to be effective only at low aw levels (Guynot et al., 2005). 

In contrast to these transformations, Michael additions of simple enolates to acceptorsubstituted dienes often yield mixtures of 1,4- and 1,6-addition products- For example, a 70 30 mixture of 1,4- and 1,6-adducts was isolated from the reaction of the lithium enolate of methyl propionate with methyl sorbate . This problem can be solved by using the corresponding silyl ketene acetal in the presence of clay montmorillonite as acidic promoter under these conditions, almost exclusive formation of the 1,4-addition product (syn/anti mixture) was observed (equation 11) . Highly regioselective 1,4-additions... 

The polymers are effective as catalysts of stereoselective hydrogenation of methyl sorbate to c/5-3-hexenoate at 160°C in cyclohexane or tetrahydrofuran. Soluble completes have been isolated after hydrogenation. Then, the catalytic activity decreases this is probably caused by the loss of Cr(CO)3 groups. The results agree with the mechanism involving the dissociation of Cr(CO)3 groups, a considerable amount of which cannot be reassociated with polymeric phenyl groups. 

Presumptive identification of a yeast suspected to be Zygosaccharomyces can be made by growing the isolate on media supplemented with 1% acetic acid. Saccharomyces sp. is not able to grow under these conditions. Further, among the species of Zygosaccharomyces, Z. bailli and Z. bisporous grow, whereas Z. rouxii will not. Other native yeast species may also be able to tolerate environmental acetic acid (Boulton et al., 1995). However, as the authors note, refermentation in sorbated sweet wine virtually eliminates these from consideration. 

The solid phase presents some fundamental differences from liquid and gas phases. First, the effect the solid has on the electronic structure of a sorbate can be profound (e.g., H2 chemidissociation on metals). Thus new processes may be energetically accessible in solid-state systems that are not important in liquid or gas phases. Second, dynamical processes in solid-state systems can be significantly different from those in liquid or gas phases. The average environment that a solute molecule encounters in gas and liquid phases is translationally invariant. This is not true for the solid with well-defined lattice sites e.g., the average environment a solute molecule sees near a lattice site is very different from that near an interstitial site. Therefore, diffusion of sorbates in or on a solid can often be treated as isolated jumps between well-defined sorption sites, and the diffusion constant can be approximated from the rate constants for isolated jumps. 

Franssen, L. R., Rumsey, T. R. Krochta, J. M. (2002). Modeling of natamycin and potassium sorbate diffusion in whey protein isolate films for application to cheddar cheese. Poster 28-5. Anaheim, CA Institute of Food Technologists Annual Meeting. 

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