Dioxane phosphate

Morphology of the enzymatically synthesized phenolic polymers was controlled under the selected reaction conditions. Monodisperse polymer particles in the sub-micron range were produced by HRP-catalyzed dispersion polymerization of phenol in 1,4-dioxane-phosphate buffer (3 2 v/v) using poly(vinyl methyl ether) as stabihzer. °° ° The particle size could be controlled by the stabilizer concentration and solvent composition. Thermal treatment of these particles afforded uniform carbon particles. The particles could be obtained from various phenol monomers such as m-cresol and p-phenylphenol. 

Figure 8. Delignification on heating (A) spruce wood meal with phosphate buffer (pH 6.8), 150°C (B) spruce wood meal with dioxane-phosphate buffer (60 40% v/v) (C) wood residue from (A) (48 h) with dioxane-phosphate buffer (60 40% v/v).

On heating wood meal with a mixture of dioxane and phosphate buffer for 48 h at 150°C, 24% of the lignin dissolved, as shown in Figure 8. Most of this lignin is hydrophobic and eluted in the retention time range GO-GO minutes (Curve B). However, when the wood residue obtained after heating wood meal with phosphate buffer was heated with the dioxane-phosphate buffer mixture, only moderate further delignification was obtained (Curve C). 

On heating wood meal for 16 h with the dioxane-phosphate buffer, 17% of the total lignin in wood dissolved. As revealed by Figure 13, about... 

Synonyms/Trade Names Delnav p-Dioxane-2,3-diyl ethyl phosphorodithioate Dioxane phosphate 2,3-p-Dioxanethiol-S,S-bis(0,0-diethyl phosphoro-dithioate) Navadel ... 

Tablets VI HPTLC CNF254 1,4-Dioxane-phosphate buffer at pH 4.4 (5 5) UV266 40-240... 

The reason that a mixtiue of 80 vol % 1,4-dioxane and 20 vol % phosphate buffer is such a good compromise for the polymerization of phenols is probably up to the formation of aggregates consisting of phenols and 1,4-dioxane. With this solvent composition, the mole fraction of 1,4-dioxane is equal to that of water [83]. Experimental data have been pubUshed which clearly indicate the formation of phenol aggregates in a 1,4-dioxane/phosphate buffer mixture [83,84]. The stabiUzation of these aggregates is best with a composition of 80 vol % 1,4-dioxane and 20 vol % phosphate buffer [83]. It seems logical that the formation of aggregates could support the recombination of radicals and the electron-transfer step. 

S >Olmethaxytrltyl>2 -d oxythylmldlne-3 -phosphate (3). A sohjllon ot 1 mmol ot 1 (T thymine, DMT-4,4 -dimethoxyti1tyl) in dioxane (8 mL), pyridine (1 mL) and a slight excess ot 2-chloro-5,6-benzo-1,3-dioxaphosphorfn-2-one 2 (1 mi. ot a 1.2S M solution in dioxane) was stirred at 20 C After 5 mki TLC Indicated complete conversion oM Into 3 with zero mobility. Water was added and after work up 3 was isolated in 88% yield. 

This easily prepared lipophilic 5 -phosphate protective group is cleaved by NCS oxidation (dioxane, triethylammonium hydrogen carbonate, 2 h, rt) followed by ammonia-induced j3-elimination. ... 

Nitrobenzaldoxime, TEA, dioxane, H20. Cleavage occurs in the presence of 4-nitrophenylethyl phosphate. 

Fig. 7.1.3 Influence of the buffer and the type of peroxide on the luminescence reaction of Chaetopterus photoprotein. The reaction was initiated at zero time by the addition of a peroxide (old dioxane or H2O2) and FeSC>4 in each case, with successive additions of FeSC>4 or H2O2 at the time indicated with an arrow. In the experiments of the two upper curves, 10 pi of old dioxane and 1 pi of lOmM FeSC>4 were added at zero time, followed by 1 pi of 10 mM FeSC>4 at each arrow. In the experiments of the two lower curves, 50 pi of 10 mM H2O2 and 20 pi of 10 mM FeSC>4 were added at zero time, followed by 50 pi of 10 mM H2O2 or 20 pi of 10 mM FeSC>4 at each arrow. All in 5 ml of 10 mM phosphate or Tris buffer, pH 7.2. From Shimomura and Johnson, 1966.

Fig. 7.1.6 Influence of pH and temperature on the luminescence of Cbaetopterus photoprotein elicited by old dioxane and Fe2+ in 20 mM phosphate buffer. Left panel the effect of pH in phosphate buffer solutions of various pH values, at 22°C. Right panel the effect of temperature at pH 7.2. Luminescence was initiated by the injection of Fe2+. The time lag of the light emission after the Fe2+ injection was also shown in the right panel. From Shimomura and Johnson, 1966.

Additional kinetic evidence supporting molecular iodine as an iodinating species is sparse. Li325 found that the iodination of tyrosine in acetate buffers at 25 °C showed the mixed inverse dependence on iodide ion concentration noted above, so that part of the reaction appeared to involve the molecular species. Subsequently, Doak and Corwin326 found that the kinetics of the iodination of (N-Me)-4-carboethoxy-2,5-dimethyl- and (N-Me)-5-carboethoxy-2,4-dimethyl-pyrroles in phosphate buffers in aqueous dioxane at 26.5 °C obeyed equation (162), viz. 

Oxidation of phenyl hexyl sulphide with sodium metaperiodate gave also only a trace amount of the corresponding sulphoxide72. On the other hand, Hall and coworkers73 prepared benzylpenicillin and phenoxymethyl penicillin sulphoxides from the corresponding benzyl esters by oxidation with sodium metaperiodate in dioxane solution with a phosphate buffer. A general procedure for the synthesis of penicillin sulphoxides was reported later by Essery and coworkers74 which consists in the direct oxidation of penicillins or their salts with sodium metaperiodate in aqueous solution at pH 6.5-7.0. 1-Butadienyl phenyl sulphoxide 4475 and a-phosphoryl sulphoxides 4576 were also prepared by the same procedure. 

The nature of the sulfonating agent (S03, free or as its dioxane—or tributyl phosphate—adduct) as well as temperature variations were shown to result in significant changes in AOS composition. 

VI a) Tricresyl phosphate, aliphatic ketones and esters, dioxane. polyesters... 

The reaction is carried out under mild neutral conditions (dioxane, room temperature, 20 h) without the need for a base such as triethylamine, as would be required if the chloridate were used instead of the imidazolide. Furthermore, yields of phosphates are higher by using the phosphoric imidazolide.[ 1873... 

An interesting hypothesis may be put forward. The interfacial pA lcm (Fig. 5.1) that a solute exhibits depends on the dielectric environment of its location in the bilayer. Simple isotropic water-miscible solvents may be used to approximate p mem pure methanol (e 32), may do well for the bilayer zone containing the phosphate groups pure 1,4-dioxane (e 2) may mimic some of the dielectric properties of the hydrocarbon region. It appears that psKa values of several weak bases, when extrapolated to 100% cosolvent, do approximate pvalues [119,162,172]. Fernandez and Fromherz made favorable comparisons using dioxane [448]. This idea is of considerable practical use, and has been largely neglected in the literature. 

A similar reaction of methyl P-D-ribopyranoside (5) with P(NMe2)3 in dioxane gave 2,3,4-bicyclophosphite of P-methyl-D-ribopyranoside, 6a in 90% yield. It was sulfurated and selenated to give the corresponding thiophosphate 6b and selenophosphate 6c in 89 and 81% yields, respectively. Oxidation of 6a with hydrogen peroxide gave cyclic phosphate 6d (92%), whereas its hydrolysis in aqueous... 

---