Dioxane acetals

The polymer is then diluted with acet and pptd in w. Post polymerization nitration is accomplished by adding 40Gml of 100% nitric acid at 0° to 25g of the dried polymer. When the polymer is completely dissolved, the excess acid is removed by distn at reduced press. The anhyd dioxane-acet soln is then pptd in methylene chloride and dried. 1... 

TLC Analysis. Samples were examined by TLC using standard procedures. Rf values were determined and compared with those of authentic reference materials. Radioactive components were located by scanning (Vanguard Instrument Corp., North Haven, Conn., Model 885) or by autoradiography (Eastman Kodak, Rochester, N. Y., type AA film). The relative Rf value of DCDD on silica gel plates (Brinkmann Instruments, Inc., Westbury, N. Y., type For,4) when developed with n-hexane dioxane acetic acid, 90 10 4, V/V/V, was 0.90. The observed impurity had a relative Rf value of 0.40. On Brinkmann alumina plates, developed with n-hexane, DCDD had a relative Rf of 0.32. Neither system separated the chlorinated dibenzodioxin isomers. 

Peroxidizable hazard on concentration Diethyl ether Tetrahydrofuran Dioxane Acetal... 

Since then, optically active a-aminophosphonates have been obtained by a variety of methods including resolution, asymmetric phosphite additions to imine double bonds and sugar-based nitrones, condensation of optically active ureas with phosphites and aldehydes, catalytic asymmetric hydrogenation, and 1,3-dipolar cycloadditions. These approaches have been discussed in a comprehensive review by Dhawan and Redmore.9 More recent protocols involve electrophilic amination of homochiral dioxane acetals,10 alkylation of homochiral imines derived from pinanone11 and ketopinic acid,12 and alkylation of homochiral, bicyclic phosphonamides.13... 

The nitrosation of A-alkylureas in dioxane-acetic acid mixtures is governed by the expression v = fc[HN02][urea], at fixed pH, and dependent on rate-determining proton transfer from the protonated iV-alkyl-iV-nitrosourea to acetate anion the order of reactivity, which reflects relative impediment by the alkyl groups, is as for nitrosation in aqueous media (methyl- ethyl- propyl- butyl- > allyl-urea). 

The oxidative procedure is based on the treatment with oxidants, preferably f-butyl hydroperoxide in refluxing dioxane, acetic acid or acetonitrile. 

Denmark SE, Almstead NG (1991) On the stereoselectivity opening of achiral dioxane acetals. J Org Chem 55 6458-6467... 

OB to CO2 minus 80.7% wh crysts (from acetone or other solvents), mp 206—208°(dec) explodes at higher temp hydrolyzed by w sol (besides acet) in ethyl acetate, Nitromethane, dioxane, acetic anhydride and acetic acid. 

Both the free and the combined forms of phenolic acids in date fruit (Phoenix dactylifera L.) were analyzed by HPLC (19). The elution rate of phenolic acids increased with the degree of hydroxylation by isocratic elution using dioxane-acetic acid (15 85) on a /zBondapak C,8 column. Ferulic acid was the most abundant in the free form, and p-coumaric, vanillic, p-hydroxy-benzoic, protocatechuic, and syringic acid were also identified in dates. 

Table III. Continuous Extraction of Wood with Dioxane, Acetals, and 0.2IV HC1...

TLC separation of DNS-amines is usually made on layers of silica gel with solvents covering a range of polarity, e.g., chloroform, ethyl acetate, diisopropyl ether and methanol. Seiler and Wiechmann [97] developed 30 solvent systems for the separation of DNS derivatives of over 100 biogenic amines on TLC plates of silica gel. The selective reaction of DNS-C1 with the amino group of catecholamines has been examined [98]. The drugs dopamine, norepinephrine and epinephrine are adsorbed on alumina which protects their hydroxyl groups from dansylation. The N-dansylated compounds are separated with benzene-dioxane-acetic acid (90 25 4) on layers of silica gel. 

Denmark, S. E. Almstead, N. G. On the stereoselective opening of achiral dioxane acetals./. Org. Chem. 1991, 56, 6458-6467. Nishiguchi, T. Fujisaki, S. Kuroda, M. Kaji-saki, K. Saitoh, M. Selective monotetrahydro-... 

Bean and Wilkinson have reported deuteriation rates for several alkyl-pyrroles in buffered aqueous dioxan-acetic acid at 25°C [78JCS(P2)72] under these conditions, neither 2-formyl- nor 2-nitropyrrole underwent exchange. Partial rate factors are given in Table 6.2. These show a number of interesting features. 

Broadbent et al. have found that the rhenium blacks prepared by reducing rhenium heptoxide are highly effective catalysts for the hydrogenation of carboxylic acids to alcohols at 150-170°C for monocarboxylic acids (eq. 10.3) and at 200-250°C for dicarboxylic acids (eq. 10.4) under 13.5-27 MPa H2.10,11 Rhenium heptoxide can be reduced to the active blacks in appropriate solvent (ethanol, 1,4-dioxane, acetic acid, or water) at 120-220°C and 15-21 MPa H2 for 1-2 h, or more conveniently, in situ in... 

A detailed study of the mechanism and origin of stereoselectivity in reactions of allyltrimethylsilane with dioxane acetals has been published. ... 

Phys. 11, 336-9 (1947). Raman Av, vapor, liquid, solution in dioxane, acetic, valeric, etc. acids. 

Raman H bonding of acetic acid with ethers, dioxane, acetal. 

Selenium dioxide oxidations may be accomplished by heating with neat substrates [5f9], but more often, they are carried out in solvents such as water, tert-butyl alcohol, ethanol, dioxane, acetic acid, and acetic anhydride. The solvent used often affects the outcome of the reaction. The use of acetic acid or acetic anhydride favors oxidation to acetates (and thence to alcohols), whereas in water or dioxane, carbonyl compounds are usually formed. An unpleasant feature of oxidations with selenium dioxide is the formation of red colloidal selenium, which cannot always be separated by distillation but can be removed by treatment of the product with potassium cyanide [522], mercury [523], or deactivated Raney nickel [524]. 

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