Esters silica

Figure 9. Enantioseparation of the precursor of Ca-sensitizing drug EMD 53998 on cellulose tris(p-methylbenzoate) beads (a) poly(N-acryloyl-aminoacid ester) silica (b) allulose tris(p-methylbenzoate) silica (Chiralal OJ) (c) and anylose tris(3,5-dimethylphenylcarbamate) silica (Chiralpak AD) (d) [153].

SMB parameters Cellulose tris(p-methyl- benzoate) beads Poly(N-acryloyl-amino acid ester) silica CSP Cellulose tris(p-methylbenzoate) coated on silica (Chiralcel OJ) Amylose tris(3,5-dimethylphenyl-carbamate) coated on silica (Chiralpak AD)... 

Ablefill JM8806/ Ablestik Labs. Moisture-resistant cyanate ester (silica filled) 3 Ceramic substrates Dispense (22-25 gauge needle), capillary underfill Flip-chip... 

Ablefill UF 8807/ Ablestik Moisture-resistant cyanate ester (silica filled) 10 Plastic, ceramic, and PWB laminates Dispense, capillary underfill CSP or BGA packages and high-density interconnect substrates... 

Cholesterol esters Silica Gel G Carbon tetrachloride/ Chloroform (95/5)... 

Chem. Descrip. Blend of esters, silica, and surfactants Uses Antifoam for industrial chem. wastewater systems Features Rapid bubble break environmentally safe Properties 100% act. 

Silyl enol ethers are other ketone or aldehyde enolate equivalents and react with allyl carbonate to give allyl ketones or aldehydes 13,300. The transme-tallation of the 7r-allylpalladium methoxide, formed from allyl alkyl carbonate, with the silyl enol ether 464 forms the palladium enolate 465, which undergoes reductive elimination to afford the allyl ketone or aldehyde 466. For this reaction, neither fluoride anion nor a Lewis acid is necessary for the activation of silyl enol ethers. The reaction also proceed.s with metallic Pd supported on silica by a special method[301j. The ketene silyl acetal 467 derived from esters or lactones also reacts with allyl carbonates, affording allylated esters or lactones by using dppe as a ligand[302]... 

R SiBr, trace MeOH. Methoxymethyl ethers are stable to these cleavage conditions. Methoxymethyl esters are unstable to silica gel chromatography, but are stable to mild acid (0.01 N HCl, EtOAc, MeOH, 25°, 16 h)." ... 

This ester is formed by standard procedures and is readily cleaved with Pd(Ph3P)4 in CH2CI2 to form trimethylsilyl esters that readily hydrolyze on treatment with water or alcohol or on chromatography on silica gel (73-98% yield). Amines can be protected using.the related carbamate. ... 

D-(-H)-Biotin 4-nitrophenyl ester [33755-53-2] M 365.4, m 160-163 , 163-165 , [a]n -n47 (c 2, MeaNCHO containing 1% AcOH). It has been recrystd by dissolving 2g in 95% EtOH (30mL), heated to dissolve, then cooled in an ice-water bath. The crystals are collected, washed with ice-cold 95% EtOH (5mL) and dried over P2O5. The Rp on silica plates (CHCl3 MeOH-19 l) is 0.19 [Bodanszky and Fagan J Am Chem Soc 99 235 1977]. 

The potential for use of chiral natural materials such as cellulose for separation of enantiomers has long been recognized, but development of efficient materials occurred relatively recently. Several acylated derivatives of cellulose are effective chiral stationary phases. Benzoate esters and aryl carbamates are particularly useful. These materials are commercially available on a silica support and imder the trademark Chiralcel. Figure 2.4 shows the resolution of y-phenyl-y-butyrolactone with the use of acetylated cellulose as the adsorbent material. 

Silica gel Aldehydes, amines, ammonia, chorophenols, esters, inorganic acid gases, methanol, nitro compounds... 

All of the eommereial alkyl eyanoaerylate monomers are low-viseosity liquids, and for some applications this can be an advantage. However, there are instances where a viseous liquid or a gel adhesive would be preferred, sueh as for application to a vertical surface or on porous substrates. A variety of viscosity control agents, depending upon the desired properties, have been added to increase the viscosity of instant adhesives [21]. The materials, which have been utilized, include polymethyl methacrylate, hydrophobic silica, hydrophobic alumina, treated quartz, polyethyl cyanoacrylate, cellulose esters, polycarbonates, and carbon black. For example, the addition of 5-10% of amorphous, non-crystalline, fumed silica to ethyl cyanoacrylate changes the monomer viscosity from a 2-cps liquid to a gelled material [22]. Because of the sensitivity of cyanoacrylate esters to basic materials, some additives require treatment with an acid to prevent premature gelation of the product. 

Note Silica gel, kieselguhr and polyamide layers can be used as stationary phases. Not all acids are stained on RP layers. Amino layers yield a pale blue background. The detection limits are in the pg range for carboxylic acids [1], thioglycolic and dithioglycolic acids [2] and for antithyroid pharmaceuticals [4] they are about 5 ng per chromatogram zone for sterols and steryl esters [6]. 

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