Dioxane solvent

The selective epoxidation of ethylene by hydrogen peroxide ia a 1,4-dioxane solvent ia the presence of an arsenic catalyst is claimed. No solvent degradation is observed. Ethylene oxide is the only significant product detected. The catalyst used may be either elemental arsenic, an arsenic compound, or both. 

Fig. 1. Produci distribution as a function of reaction time in cobalt-catalyzed CO hydrogenation. (Reprinted from Ref. 38, by courtesy of Marcel Dekker, Inc.) Reaction conditions 26.5 atm H2, 340 atm CO, 182 C, 1,4-dioxane solvent. Y = J 0[HCo(CO)4]dt cobalt concentration changes throughout reaction because of sampling. Average HCo(CO)4 concentration is 0.051 M.

Data from Ref. 38, by courtesy of Marcel Dekker, Inc. b Turnover frequency, moles of product per mole of catalyst per hour. c 1,4-Dioxane solvent. 

The indicated first-order rate dependence on [HCo(CO)4] is observed in 1,4-dioxane solvent, as shown by the constant value of k over a range of HCo(CO)4 concentrations. A slightly higher concentration dependence may be observed in 2,2,2-trifluoroethanol (e.g., Expt. 9). It is proposed that such behavior, if significant, could be the result of greater ionic dissociation of HCo(CO)4 at the lower concentrations in this more polar solvent. A catalyst concentration effect on product selectivity was reported by Keim et al. (59), but rate effects are not reported and possible secondary reactions are not taken into account. 

Solvent 1,4-dioxane. Solvent DMSO. Solvent n-hexane. Solvent trichloromethane. n->7t superposed by n->n ... 

Figure 1.3 Plots of equilibrium monomer concentrations ([DX]eq) on monomer concentration in the feed ([DX]o) as obtained in a DX/tin octoate (Sn(Oct)2)/BuOH polymerization system. Conditions [Sn(Oct)2]o = KT rnol I". Open symbols indicate polymerization in 1,4-dioxane solvent solid symbols indicate bulk polymerization. Temperatures (in °C) 80 (O, ), 100 ( , ) and 120 (A, A).

Entry 4 shows that reaction of a secondary 2-octyl system with the moderately good nucleophile acetate ion occurs wifii complete inversion. The results cited in entry 5 serve to illustrate the importance of solvation of ion-pair intermediates in reactions of secondary substrates. The data show fiiat partial racemization occurs in aqueous dioxane but that an added nucleophile (azide ion) results in complete inversion, both in the product resulting from reaction with azide ion and in the alcohol resulting from reaction with water. The alcohol of retained configuration is attributed to an intermediate oxonium ion resulting from reaction of the ion pair with the dioxane solvent. This would react until water to give product of retained configuratioiL When azide ion is present, dioxane does not efiTectively conqiete for tiie ion-p intermediate, and all of the alcohol arises from tiie inversion mechanism. ... 

Another general method for converting alcohols to halides involves reactions with halides of certain nonmetallic elements. Thionyl chloride, phosphorus trichloride, and phosphorus tribromide are the most common examples of this group of reagents. These reagents are suitable for alcohols that are neither acid sensitive nor prone to structural rearrangement. The reaction of alcohols with thionyl chloride initially results in the formation of a chlorosulfite ester. There are two mechanisms by which the chlorosulfite can be converted to a chloride. In aprotic nucleophilic solvents, such as dioxane, solvent participation can lead to overall retention of configuration.7... 

Table 10.9 Heavy atom KIEs on decarboxylation of 4-pyridylacetic acid at 25 °C in water-dioxane solvents (Sicinska, D., Truhlar, D. G. and Paneth, P., J. Am. Chem. Soc. 123, 7683 (2001) and J. Phys. Chem. B 106, 2708 (2002)) ...

Data from Reference 12 in dioxane solvent unless otherwise noted. ... 

The Wittig-Horner (W-H) reaction is a versatile method for the synthesis of functionalized alkenes. The synthesis of 3-substituted ethyl acrylates and acrylonitriles, which are used as monomers in polymerization, were successfully carried out by the reaction of triethyl phosphonoacetate or cyanomethanephosphonate, respectively, with various aldehydes with activated Ba(OH)2 as the catalyst in the presence of dioxane solvent at 343 K (294). As was observed for other basic solid... 

Synthesis of acyclic -alpha-enones was performed according to the Wittig-Horner 297) and Claisen-Schmidt 298) approaches with activated Ba(OH)2 as a basic catalyst (Scheme 47). The W-H reactions were carried out in the presence of dioxane solvent at 343 K, and yields higher than 90% were observed after reaction times between 10 and 30 min in a batch reactor. Under these conditions, owing to the dependence of the reaction course on the acidity of the phosphonate with barium hydroxide, the W-H reaction took place in a homogeneous phase. 

The addition of 16% water to dioxane solvent was found to increase the... 

Dioxane is extensively used as a solvent for cellulose acetate, fats, greases, etc (Ref 14) It was tried on the laboratory scale by Aaronson at PicArsn (Ref 6) as a plasticizer for NC s and found to be a fairly good solvent for Collodion Cotton and Pyrocellulose, but rather poor solvent for Guncotton and High Nitrogen NC (14% N). The resulting jels were very toxic and their dioxane solvent was very difficult to remove by evaporation. This made dioxane an undesirable solvent for NC s, much inferior to acetone and propylene oxide... 

Fig. 16. Effect of degree of crosslinking (% DVB) of standard (non-porous) ion exchanger on initial transesterification rate, r° (mol kg-1 h-1), of ethyl acetate with 1-propanol [436]. (1) Liquid phase at 52°C initial composition (mole%), 0.4 ethyl acetate, 0.4 1-propanol, 0.2 dioxan (solvent). (2) Vapour phase at 120°C partial pressure of reactants, 0.5 bar (ester—alcohol ratio 1 1).

The condensation of the silanols to siloxanes in non-protic organic solvents proceeds to completion. Lasocki has observed that the rate of silanol condensation is affected by small amounts of water added to the non-protic (dioxane) solvent [68]. The maximum effect is observed at approximately 0.75 M water. The impact of water on the rate may be due to solvation of ionic intermediates, its effect on the activity of the acids or bases, and its effect on the polarity of the solvent. 

The catalytic function of the KOH/DMSO system in heterocyclization of ketoximes with acetylene is manifested when mixed DMSO/dioxane solvent is used. The results obtained for the reaction of cyclohexanone... 

Because the rates of this reaction are very rapid, normal sampling techniques were not satisfactory and an infrared technique was used. This esterification reaction was shown to be about 100 times faster than the disproportionation reaction and inter-intra-molecular assistance was also found to be important. This assistance seems to be a common pattern in acid-catalysed processes of oligosiloxanols in inert solvents. In dioxane solvent the redistribution kinetics can be interpreted in terms of an unzipping mechanism. The ratedetermining step is terminal silanol cleavage by water forming dimethylsilanediol which rapidly reacts with other substrate silanols (Scheme 4). 

Summary TATB can be made by reacting dry ammonia gas with 1,3,5-trichloro-2,4,6-trinitrobenzene in dioxane solvent. The resulting precipitated product is then filtered-off, washed, and then dried. Commercial Industrial note For related, or similar information, see Serial No. 813,039, May 13th, 1959, by The United States Navy, to Lloyd A. Kaplan, Adelphi, MD, and Francis Taylor, Jr., Baltimore MD. Part or parts of this laboratory process may be protected by international, and/or commercial/industrial processes. Before using this process to legally manufacture the mentioned explosive, with intent to sell, consult any protected commercial or industrial processes related to, similar to, or additional to, the process discussed in this procedure. This process may be used to legally prepare the mentioned explosive for laboratory, educational, or research purposes. 

Electromotive force measurements of HC1 solutions in pure NMA and in NMA/dioxane solvent mixtures using the silver-silver chloride electrode have been reported by Dawson and his co-workers (1,2,3). The only other potentiometric studies in a solvent of dielectric constant higher than that of water appear to have been in formamide (6,7,8,9, 10) and in N-methylpropionamide (NMP) (11,12,13,14,15). 

Until relatively recently no kinetic studies on the nitrosation of alcohols had been reported, presumably since the reactions are very rapid and require special techniques. Some kinetic measurements on the reverse reaction, the hydrolysis of alkyl nitrites have been reported here conventional kinetic methods were used. Early workers examined the reactions of the series methyl, ethyl, i-propyl and t-butyl nitrites in an acetic acid-acetate buffer and found a small increase in rate constant along the series (Skrabal et a ., 1939). Later Allen measured the rate constants for the hydrolysis of a number of alkyl nitrites in aqueous dioxan solvent for both acid- and base-catalysed reactions (Allen, 1954). The rate constants for the O-nitrosation of alcohols were determined indirectly by measurement of the overall equilibrium constant for the process, by noting the change in the rate constant for the nitrosation of phenol in the presence of added alcohols. These, combined with the known data for the reverse hydrolysis reaction, enabled the rate constants for the forward reaction to be obtained (Schmid and Riedl, 1967). The reactivity sequence MeOH > EtOH > i-PrOH > t-BuOH was deduced, and attributed to a steric effect. 

The solvent effects on rates shown by these two reactions were determined employing the solvents chloroform, dichloromethane, acetonitrile, ethyl acetate, benzene, tetrahydrofuran and dioxane. Solvents which react with TCNE, such as nitromethane, dimethylformamide and protic solvents, as well as cyclohexane, carbon tetrachloride and tetrachloroethylene, in which the reactants have very low solubility, were deliberately excluded from the study. The observed solvent effects were virtually identical for both Diels-Alder and [2 + 2] cycloaddition processes. Statistical correlations of rate data using a multiparameter equation with dependencies based on acceptor properties, polarizability and inherent polarity of the solvents gave nearly identical coefficients through the regression analyses for each term for both reactions, and excellent linear fits to the rate data. 

Figure 21. Dependence of the lifetime of the CS state of 23( ) on the number of intervening a bonds for benzene and dioxane solvents. The straight lines drawn through the data (extended as a dashed line for benzene) correspond to an exponential dependence of the charge recombination lifetime, on n [74], Note that the experimentally determined charge recombination lifetime. t , is not necessarily equal to l/it , because it also includes a contribution from the lifetime of the BET process...

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