Acetals stability

Grassie and coworkers [136,137] carried out a comparative study of the thermal degradation of vinyl chloride-vinyl acetate copolymers covering the entire composition range. They observed that <10% of vinyl acetate produced a marked decrease in stability as compared with PVC. Thereafter, there was a progressive decrease in stability as the amount of comonomer was increased with a minimum at 40-50% vinyl acetate. Stability progressively increased with further increase in... 

Figure 3.9 Calculated electrostatic potential maps for acetate anion and ethoxide anion. Although both molecules carry the same -1 net charge, acetate stabilizes the charge better by dispersing it over both oxygens.

L. Wu, J. Chen, D. Du, and H. Ju, Electrochemical immunoassay for CA125 based on cellulose acetate stabilized antigen/colloidal gold nanoparticles membrane. Electrochim. Acta 51, 1208-1214 (2006). 

Remarkably, the cycloaddition of acrolein at the intermediate cobaltacycle selectively occurs at the carbonyl-, rather than at the C,C double bond, to give a vinylpyrane. In this cycloaddition, methyl acetate stabilizes the cpCo complex (87MI6) [Eq.(37)]. 

All the above-mentioned processes are similar in a CH3CN-pyridine (v/v = 9/1) mixture32. However, the disproportionation rate of Co1 which is electrogenerated at — 1.30 V/SCE and its oxidative addition rate to various arylhalides are divided by a factor of two compared to the rate constants determined in DMF-pyridine. It has also been shown that the use of vinyl acetate stabilizes Co1 species. Under these conditions, the disproportionation rate constant is divided by a factor of seven whereas the oxidative addition rate constants are not much affected. 

Converse flexoelectric effects (i.e. voltage-generated curving) have been demonstrated in uranyl-acetate-stabilized phosphatidylserine BLMs by real-time stroboscopic interferometric measurements the obtained satisfactory agreement between the converse and the direct (i.e. curvature-generated voltage) flexoelectric coefficients have been in accord with the Maxwell relationship [8]. 

Less is known concerning the partial, acid hydrolysis of alditol polyacetals derived from ketones, compared to those derived from aldehydes. The acid hydrolysis of 1,2 3,4 5,6-tri-O-isopropylidene-D-mannitol to 3,4-O-isopropylidene-D-mannitol55,56 and of l,2 3,4-di-0-isopropylidene-L-rhamnitol to 3,4-O-isopropylidene-L-rhamnitol57 indicates an order of isopropylidene acetal stability of a-threo > a, and this order is supported by the partial hydrolysis of 2,3 4,5-di-O-isopro-pylidene derivatives of dialkyl dithioacetals of D-arabinose58 and D-xylose59 to 2,3-acetals. 

Other groups have subsequently reported anion receptors that work on the same principle. For instance, an Eu(III) complex of the bis-bipyridinephen-ylphosphine oxide ligand 86 made by Ziessel and co-workers is able to sense anions by luminescence enhancement in acetonitrile, with stability constants which follow the trend fluoride>acetate>chloride>nitrate [61]. Tsukube and co-workers have investigated the properties of the Eu(III) and Tb(III) complexes of the chiral ligand 87 [62]. Anion binding was assessed by profiling luminescence enhancement in acetonitrile, and it was found that the different metal centres provided different selectivities. The emission at 548 nm of the Tb(III) complex was increased by 5.5 times in the presence of 3 equivalents of chloride compared to 2.2 for nitrate and 1.1 for acetate. Conversely the emission at 618 nm of the Eu(III) complex was increased 8.3 times by 3 equivalents of nitrate, 2.5 times for chloride and 1.0 times for acetate. Stability constants were not reported. 

Zirconia particles are difficult to maintain in transparent suspensions. Acetate stabilized (1.5 mole/mole ZrC>2) 5-10 nm particles, up to 20% weight were used in these studies [22], All experiments were conducted at pH 3.4 in solutions containing 2.76 M acetic acid. Under these conditions the majority of electrons are converted to hydrogen atoms. Electrophoresis of diluted suspensions shows that the surface charge of the particles is positive and the point-of-... 

Stabilizer 1097. [Miles/Polysar Rubber] Acid chloride in butyl acetate stabilizer used to extend the pot life of the btmding agent system/piastisol mixt... 

Aluminum Acetate Solution. Burow s Solution Domeboro. Contains about 5% neutral aluminum acetate. A (CjHjOj) = 0.66% Al, 4.4% acetic acid (1.25% A12Oj> Prepn from a dry mix consisting of an alkali metal acetate, acetic acid and a dibasic aluminum acetate stabilized with boric acid Gibbons et al, U.S. pat. 2,824,042 (1958). 

Experimental observation of selective flocculation. Croucher and Hair (1980a) have demonstrated the phenomenon of selective flocculation in mixtures of heterosterically stabilized dispersions. They prepared particles of poly(vinyl acetate) stabilized by polystyrene and polyacrylonitrile particles stabilized by polyisobutylene, both in cyclopentane. The value of X23 for polystyrene and polyisobutylene is known to be positive (Hyde and Tanner, 1968), corresponding to mutually incompatible polymers. The poly(vinyl acetate) particles stabilized by polystyrene exhibited both upper and lower critical flocculation temperatures whereas the polyisobutylene stabilized particles only flocculated on heating. 

The previous route provided us with some key encouraging clues and the acetal stability troubles easily signaled a way forward (Scheme 17). We decided to simply reduce ester 87 to an aUyUc alcohol (88) and to examine whether... 

Oleth-2 Oleth-10 PPG-2 isoceteth-20 acetate stabilizer, freeze/thaw latex Nonoxynol-8... 

In 2005, we employed acetate stabilized ruthenium(0) nanoparticles as catalyst for the hydrolysis of SB, which is known to be the first example of nanoparticles catalyst used for this reaction [50]. Water dispersible ruthenium(0) nanoparticles are formed from the reduction of ruthenium(III) chloride in the presence of acetate anion as stabilizer. The acetate stabilized ruthenium(O) nanoparticles of 2.8 1.4nm particle size were found to be highly active catalyst in the hydrolysis of sodium borohydride even at room temperature and low catalyst concentration (Figure 7.2). The acetate stabilized ruthenium(O) nanoparticles provide 5170 TTO (total... 

FIGURE 7.2 (a) TEM image of acetate stabilized ruthenitim(0) nanoparticles prepared from the reduction of 1.33mM ruthenium(III) chloride trihydrate by 9.3 mM sodium borohydride in the presence of l.OM acetate ion in aqueous solution, (b) plot of the volume of hydrogen (mL) versus time (s) for the hydrolysis of sodium borohydride catalyzed by ruthenium(O) nanoparticles with different catalyst concentrations at 25.0 0.1 °C. [NaBH4lo=150mM. 

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