Dioxane solutions

Dissolve 10 g. of chloro- 2,4-dinitrobenzenet in 50 ml. of dioxan in a 250 ml. conical flask. Dilute 8 ml. of hydrazine hydrate with an equal volume of water and add this slowly with shaking to the dioxan solution, keeping the temperature between zo " and 25°. Heat under reflux for 10 minutes to complete the reaction and then add 5 ml. of ethanol and heat again for 5 minutes. Cool and filter oflF the orange 2,4-dinitrophenylhydra-zine. Recrystallise the dry product from ethyl acetate m.p. 200° (decomp.). Yield, 7 g. 

In order to prepare an acid, a dioxan solution of the diazo ketone is added slowly to a suspension of silver oxide in a dilute solution of sodium thiosulphate Iftheco)iversion to the acid yields unsatisfactory results, it is usually advisable to prepare the ester or amide, which are generally obtained in good yields hydrolysis of the derivative gives the free acid. 

Chlorination of the azobenzene complex 463 with chlorine produces mono-chloroazobenzene with regeneration of PdCN. Then complex formation takes place again with the chlorinated azobenzene. By this sequence, finally tetra-chloroazobenzene (503) is obtained using a catalytic amount of PdCT. The reaction, carried out by passing chlorine gas into an aqueous dioxane solution of azobenzene and PdCf for 16 h, gives a mixture of polychlorinated azoben-zenes[455]. 

This reaction is explosive and proceeds in low yield (—21%) because of the instability of the thioformamide that is destroyed as soon as it is cyclized with 1 (113,491). The thioformamide is better prepared directly in the reaction mixture by condensing phosphorus pentasulfide and for-mamide at room temperature, in dioxane solution, according to reaction 1 (491,492),... 

For example, with thioacetamide prepared in situ in dioxane solution at 45 C, Cottet and Metzger (578) prepared the 4-methylthiazole (3), R] = Me, in 39% yield, while Erlenmeyer et al. (285) obtained a similar result in benzene and acetic anhydride. 

Syntheses of a,)3-dihalogenoethers can be achieved in various ways the classical method (37), wherein a current of dry gaseous hydrochloric acid, is made to react in an equimolar mixture of ethanol and aldehyde at 20°C first to form the monochloroether (50% yield) and then by the action of bromine, the dibromoether (80 to 90% yield) can be used. The second and simpler method is the direct bromination of ethylvinylether in a chloroformic or dioxane solution if the product is used directly without purification,... 

The reaction can be carried out in two steps (641). First, equimolar amounts of amide and phosphorus pentasulfide are mixed under stirring in dioxane, the temperature being kept below 45°C. After 20 minutes, the a-halocarbonyl compounds (in dioxane solution) are added in small portions. At the end of the addition the temperature reaches 80 to 100°C, and the reaction mixture is kept at this temperature for another hour. 

Virtually all of the organo derivatives of CA are produced by reactions characteristic of a cycHc imide, wherein isocyanurate nitrogen (frequendy as the anion) nucleophilically attacks a positively polarized carbon of the second reactant. Cyanuric acid and ethylene oxide react neady quantitatively at 100°C to form tris(2-hydroxyethyl)isocyanurate [839-90-7] (THEIC) (48—52). Substitution of propylene oxide yields the hydroxypropyl analogue (48,49). At elevated temperatures (- 200° C). CA and alkylene oxides react in inert solvent to give A/-hydroxyalkyloxazohdones in approximately 70% yield (53). Alternatively, THEIC can be prepared by reaction of CA and 2-chloroethanol in aqueous caustic (52). THEIC can react further via its hydroxyl fiinctionahty to form esters, ethers, urethanes, phosphites, etc (54). Reaction of CA with epichlorohydrin in alkaline dioxane solution gives... 

When the reaction is performed in dioxane solution, an o onium ion is formed from the solvent and the chlorosulfite ester. The oxonium ion then undergoes substitution by chloride. l vo inversioRs are involved so that tiie result is overall retention. ... 

In a typical case, ethylamine is allowed to react with ethylene oxide to produce N-ethyldiethanolamine (5). The latter is then treated with additional ethylene oxide to afford N,N-di(polyoxyethylene)ethylamine (6) where the sum a -t b is 3. This material is then stirred at room temperature for 3 h with toluenesulfonyl chloride and powdered sodium hydroxide in dioxane solution. After filtration and Kugelrohr distillation, N-eth-ylmonoaza-15-crown-5 is isolated in 75% yield as illustrated below in Eq. (4.7). 

Photolysis of a dioxane solution of (2) using a 250 watt quartz lamp also provides 16a,17a-methylene-20-ketones (4). ... 

Dehydrotestosterone acetate (174) in nonprotic solvents (dioxane, benzene) undergoes a rearrangement to the isomer (175). This product is photolabile and isomerizes readily to new cross-conjugated dienones. Thus, ultraviolet irradiation of (174), its 1-, 2- and 4-methyl homologs, and its lOa-stereoisomer (188) in dioxane solution causes, in each case, a series of rearrangements as summarized on page 331 for (174) and (188). ... 

While the mechanistic scheme as outlined so far accounts for the majority of structural changes in ring A-dienone isomerizations, a few cases require modifications of this general pathway. The B-nor dienone (215) is transformed exclusively to the linear dienone (217) in dioxane solution. The preferential fission of the 5,10-bond in the hypothetical precursor (216) has... 

In dioxane solution at 30°C, content of IH tautomer is 60 10% according to dipole moment measurements (80JHC1373). 

Boiled in a water-dioxane solution in the presence of acids, these compounds turn into l-alkyl-3-propynyl-5-methylpyrazoles (Scheme 25). 

In the hydrogenation, 200 g of acetophenone azine, 1000 ml of EtOAc and 5 g of 10% Pd-on-C was shaken at 30-50 psig for 10 h. Hydrogen absorption had ceased. About 7.6 g of phenylethylamine, formed by cleavage of the N—N bond, was obtained as a by-product. Oxidation of hydrazines can be done catalytically. Ethyl 2-arylhydrazine carboxylates were oxidized easily by bubbling air at 25 "C through a toluene or dioxane solution in the presence of Pd or Pt (5d). 

Hydrocortisone (25 g) and Bendazac chloride (21 g) are suspended in anhydrous dioxane (250 ml). Pyridine (6 ml) is added and the solution is kept under stirring for 2 hours at room temperature, Pyridine hydrochloride which separates is filtered and the clear dioxane solution is added, under strong stirring, to a solution of sodium bicarbonate (20 g) in distilled water (2,500 ml). The colorless precipitate which is formed is filtered, washed with water and dried on a porous plate. The substance crystallizes from ethanol. Needles. MP 174°-176 t Yield 75%. 

Azido-5-chloroisoquinoline (18) in methoxide/methanol/dioxane solution undergoes ring expansion to the 5//-pyrido[3.4-c]azepine 19 accompanied by its hydrolysis product, the py-ridoazepinone 20. 5//-Pyrido[3,4-c]azepin-9(8//)-one is the main product from the photolysis of 5-azidoisoquinoline under the same conditions.151... 

An elegant extension of these ring expansions involving diazidonaphthalenes has been reported. Early results on the photolysis of 1,8-diazidonaphthalene (14) indicated the formation of benz[t d]indazole (17).176 However, it has since been found that photolysis of the diazide in sodium methoxide-methanol/dioxane solution for a short period (20 -40 min) yields, in addition to the benz[c,d]indazole (17, 40%), a mixture of 9-azido-l-methoxy-5//-2-benzazepine (15 15-20%) and l,10-dimethoxy-5,5a-dihydroazepino[3,4-c]azepine (16 10-15%).117... 

Further investigation of this reaction using dioxan solutions of various water content, indicated that the reaction was second-order in 90-95 vol. % aqueous dioxan, but the order decreased, along with the reaction rate, to one in 60-80 vol. % aqueous dioxan618. However, under the latter conditions the reaction rate was still dependent upon the concentration of hydrochloric acid, and it was proposed that here the mechanism is SE1, equilibria (247) and (248), 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. 

Transient absorption spectra were measured with PBS in dioxane solution. In aerated solution the absorption decayed by two processes, a rapid one with f 1/2 50 /rs and a slow one with fj/2 20ms. In argon-saturated solution, a relatively weak absorption which decayed with f1/2 20ms was observed. The rate of the rapid decrease in the optical density agrees with that of the decrease in the intensity of the scattered light. 

The dichlorodibenzo-p-dioxin component was isolated by passing a dioxane solution of the mixture through acetate ion exchange resin to remove phenolics. The eluted product was recrystallized from benzene. The x-ray powder diffraction pattern of the precipitate was identical with that of 2,7-dichlorodibenzo-p-dioxin. Analysis of the mother liquor by GLC showed a singular peak consistent with 2,7-dichlorodibenzo-p-dioxin. The mother liquor was cooled to 5°C and yielded transparent crystals. This material had an x-ray diffraction pattern congruent to a sample of 2,8-dichlorodibenzo-p-dioxin obtained from A. E. Pohland (FDA). The two patterns were quite distinct from each other 14, 15). 

In the case of the hexacarbonyls, the rate-expression contains not only the same type of first-order term but in addition one second-order overall. For good entering groups (but not CO, for example) the rate expression contains a term strictly first-order in both the complex and the entering nucleophile. The first-order rates of CO exchange are practically identical with the rates of substitution in hydrocarbon solvents, but there is nevertheless some acceleration in ether (THF, dioxan) solutions. This solvent-dependence is not so well-marked ° as in the case of nickel tetracarbonyl. The second-order rate of substitution very strongly depends upon the basicity of the entering nucleophile... 

The reversible oxygenation of Fe(DMG)2 (B)2 in aqueous dioxane solution, as monitored by reversible changes in the visible absorption spectrum and manometric oxygen evolution, has been reported (55), but in a more recent study 54) it was not possible to confirm the earlier findings. However it was established that there was a slow irreversible... 

Dipole moments for dioxan solutions of both CHO or P-Cl terminated dendrimers were measured at 25 °C. Remarkably, values of dipole moment vs generation increase exponentially from 8.43 (10-[G1])to258 (10-[G10]) and from 8.27 (10-[G ]) to 328 (10-[GnD debyes (Fig. 10a), the highest dipole moment values... 

The data given below are typical of the polymerization of vinyl phenylbutyrate in dioxane solution in a batch reactor using benzoyl peroxide as an initiator. The reaction was carried out isothermally at 60 °C using an initial monomer concentration of 73 kg/m3. From the following data determine the order of the reaction and the reaction rate constant. Note that there is an induction period at the start of the reaction so that you may find it useful to use a lower limit other than zero in your integration over time. The reaction order may be assumed to be an integer. 

The reaction of cyclohexanol and acetic acid in dioxane solution as catalyzed by sulfuric acid was studied by McCracken and Dickson Ind. Eng. Chem. Proc. Des. and Dev., 6 (286), 1967]. The esterification reaction can be represented by the following stoichiometric equation. 

Marvel, Dec, and Cooke [J. Am. Chem. Soc., 62 (3499), 1940] have used optical rotation measurements to study the kinetics of the polymerization of certain optically active vinyl esters. The change in rotation during the polymerization may be used to determine the reaction order and reaction rate constant. The specific rotation angle in dioxane solution is a linear combination of the contributions of the monomer and of the polymerized mer units. The optical rotation due to each mer unit in the polymer chain is independent of the chain length. The following values of the optical rotation were recorded as a function of time for the polymerization of d-s-butyl a-chloroacrylate... 

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