Heterogeneous preparation

S. L. Buell and J. N. Demas, Heterogeneous preparation of singlet oxygen using an ion exchange boundtris(2,2 -bipyridine)ruthenium(II) photosensitizer, /. Phys. Chem. 87, 4675 1681 (1983). 

Heterogeneous preparation of acyl cyanides from the corresponding chlorides with potassium cyanide powder in acetonitrile is promoted by the addition of a small amount of water l or by ultrasonic irradiation under dry conditions. comparison with the former method, which requires the optimization of the water amount for each substrate, the latter method is more convenient, as shown in the following procedure. A mixture of... 

The adjuvant activity of saponins has been known for more than 50 years [10]. Commercially available saponins frequently consist of highly heterogeneous preparations of varying composition, sometimes being little more than crude extracts of the bark of the South American soap tree, Quillaja saponaria (Rosaceae), which may be contamined with tannins. The major components, however, are bidesmo-sidic quillaic acid triterpene-saponins [10]. 

Mo Z-1, Zhao Z-1, Chen H, Niu G-P, Shi H-f. Heterogeneous preparation of cellulose-polyaniline conductive composites with cellulose activated by acids and its electrical properties. Carbohydr Polym 2009 75 660-664. 

Some further attempts at the chemical and phydcochemical characterization of transfer RNA were also made. Although base compositions of grossly heterogeneous preparations such as sRNA are not particularly significant, it may be significant that the more active fractions were found to have a higher content of pseudouridine than the less active ones (82). 

It should be remembered, however, that the group name does not imply a specific substance but designates a heterogeneous preparation which has been obtained by a specific extraction procedure. 

Mo, Z.L., Zhao, Z.L., Chen, H., Niu, G.P., Shi, H.F., 2009. Heterogeneous preparation of cellulose—polyaniline conductive composites with cellulose activated by adds and its electrical properties. Carbohydrates Polymer 75, 660—664. 

Derivatives of hemicellulose components have properties similar to the ceUulosic equivalents but modified by the effects of thek lower molecular weight, more extensive branching, labile constituents, and more heterogeneous nature. Acetates, ethers, carboxymethylxylan (184), and xylan—poly(sodium acrylate) (185) have been prepared. 

The methodology for preparation of hydrocarbon-soluble, dilithium initiators is generally based on the reaction of an aromatic divinyl precursor with two moles of butyUithium. Unfortunately, because of the tendency of organ olithium chain ends in hydrocarbon solution to associate and form electron-deficient dimeric, tetrameric, or hexameric aggregates (see Table 2) (33,38,44,67), attempts to prepare dilithium initiators in hydrocarbon media have generally resulted in the formation of insoluble, three-dimensionally associated species (34,66,68—72). These precipitates are not effective initiators because of their heterogeneous initiation reactions with monomers which tend to result in broader molecular weight distributions > 1.1)... 

Oleoresin. Natural oleoresins are exudates from plants, whereas prepared oleoresins are solvent extracts of botanicals, which contain oil (both volatile and, sometimes, fixed), and the resinous matter of the plant. Natural oleoresins are usually clear, viscous, and light-colored Hquids, whereas prepared oleoresins are heterogeneous masses of dark color. 

Heterogeneous Catalytic Polymerization. The preparation of polymers of ethylene oxide with molecular weights greater than 100,000 was first reported in 1933. The polymer was produced by placing ethylene oxide in contact with an alkaline-earth oxide for extended periods (61). In the 1950s, the low yield and low polymerization rates of the eady work were improved upon by the use of alkaline-earth carbonates as the catalysts (62). 

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