Anion water-acetone

Water-acetone mixtures offer a sufficiently polar medium that certain alkyl halides can dissociate into a halide anion and a carbocation. The latter then reacts with water to give an SnI substitution product. 

The reaction is likely to be a reverse of the aldol condensation (e.g. reaction 4.20). The first step involves equilibration of the kelo alcohol with its anion. This is followed by a rate-determining fragmentation of the anion to acetone and the acetone anion, which will rapidly be converted by water into a second acetone molecule. Since the second step will be rate determining, the rate will be proportional to the concentration of the anion formed in the first step, which will be proportional to [OH ][Me2C(OH)CH2COMe] ... 

The compound (NH4)2Pt(Ss)3 is a brick-red crystalline solid soluble in water, acetone, and pyridine but insoluble in chloroform or diethyl ether. It shows no melting point but turns black at 145-150°. The complex anion is readily precipitated from aqueous solution by large cations. The infrared spectrum (mineral oil mull) shows weak S—S modes at 490 and 450 cm 1 additional weak bands are observed at 292 and 273 cm 1 in addition to the anticipated higher-energy NH4 modes. 

The addition of cosolvents to ionic liquids can result in dramatic reductions in the viscosity without changing the cations or anions in the system. The haloalu-minate ionic liquids present a challenge due to the reactivity of the ionic liquid. Nonetheless, several compatible co-solvents have been investigated, including benzene, dichloromethane, and acetonitrile [13-17]. The addition of as little as 5 wt.% acetonitrile or 15 wt.% of benzene or methylene chloride was able to reduce the absolute viscosity by 50% for [EMIMjCl-AlCls ionic liquids with less than 50 mol% AICI3 [13]. Non-haloaluminate ionic liquids have also been studied with a range of co-solvents including water, acetone, ethanol, methanol, butanone, ethyl acetate, toluene, and acetonitrile [6,18-22]. The ionic liquid response is similar to that observed in the haloaluminate ionic liquids. The addition of as little as 20 mol% co-solvent reduced the viscosity of a [BMIM][BF4] melt by 50% [6]. 

Table 3 summarizes the results at low temperatures in this solvent mixture. These data show the hydration numbers n to be markedly sensitive to the type and the concentration of the anion, Low estimates of n were attributed to either replacement of water in the primary coordination sphere by the CIO4 or NO3 ions or to changes in water activity in solution as a result of hydrogen bonding between water and acetone (Brucher et al. 1985). Such hydrogen bonding has been detected by H-NMR spectroscopy in water-acetone mixtures at very low water content (Takahashi and Li 1966) and could involve either A. . . HOH or A. .. HOH. .. A species, depending on the relative concentrations of water and acetone. 

We shall see later (p. 396, 3f) that on replacing the aqueous medium by water-alcohol or water-acetone mixtures similar term displacements can occur in this series of three terms (p. 398, Fig. 43) as we have discussed above for the terms of the anion series with the positive ichthyocoll sol. 

Solvation of UOj ions in water-acetone and water-dioxane mixtures was studied by ultrasound and H-NMR techniques and the estimated hydration numbers given in table 4 (Ernst and Jezowska-Trzebiatowska 1975a, b). The results indicate a decrease in the hydration numbers with increasing dioxane concentration. This was attributed to a probable partial replacement of waters of hydration by the organic solvent although inner-sphere complexation by the anion would also reduce the hydration number. 

What is the strength of the base required to produce an enolate anion from a carbonyl compound The strongest base that can exist in aqueous solution is the hydroxide ion. Because the pA of water is 15.7 and the pA of acetone is 19, the amount of the enolate anion of acetone that can form in a 1 M NaOH solution is very small. Although the concentration of enolate is low, it may be sufficient for some reactions. As the enolate reacts, more enolate forms, maintaining the equilibrium. 

Ionic Nature Anionic/nonionic Uses Detergent aux., solubilizer for alkaline cleaners Features Solubilizes most nonionic surfactants in presence of inorg. salts Properties Hazen < 150 paste sol. 5% in water, acetone, ethanol, trichlorethyl-ene, wh. spirit, xylene sol. si. hazy in propylene glycol dens. 1060 kg/m vise. 2000 mPa s pour pt. 23 C cl. pt. 30 C pH 2 (1% aq.) surf. tens. 28 mN/m (0.1 %) Draves wetting > 46 s (0.1 %) Ross-Miles foam 30 mm (initial, 0.05%, 50 C) 100% act. 

Suitable catalysts include the hydroxides of sodium (119), potassium (76,120), calcium (121—125), and barium (126—130). Many of these catalysts are susceptible to alkali dissolution by both acetone and DAA and yield a cmde product that contains acetone, DAA, and traces of catalyst. To stabilize DAA the solution is first neutralized with phosphoric acid (131) or dibasic acid (132). Recycled acetone can then be stripped overhead under vacuum conditions, and DAA further purified by vacuum topping and tailing. Commercial catalysts generally have a life of about one year and can be reactivated by washing with hot water and acetone (133). It is reported (134) that the addition of 0.2—2 wt % methanol, ethanol, or 2-propanol to a calcium hydroxide catalyst helps prevent catalyst aging. Research has reported the use of more mechanically stable anion-exchange resins as catalysts (135—137). The addition of trace methanol to the acetone feed is beneficial for the reaction over anion-exchange resins (138). 

Early patents indicated that because water inhibits the aldol condensation mechanism, it was necessary to dry recycle acetone to less than 1% water (139—142). More recent reports demonstrate DAA production from waste acetone containing 10—50% water (143), and enhanced DAA production over anion-exchange resins using acetone feeds that contain 3—10% water (144,145). 

Physical and Chemical Properties. Sodium thiocyanate [540-72-7] NaSCN, is a colorless dehquescent crystalline soHd (mp 323°C). It is soluble in water to the extent of 58 wt % NaSCN at 25°C and 69 wt % at 100°C. It is also highly soluble in methanol and ethanol, and moderately soluble in acetone. Potassium thiocyanate [333-20-0] KSCN, is also a colorless crystalline soHd (mp 172°C) and is soluble in water to the extent of 217 g/100 g of water at 20°C and in acetone and alcohols. Much of the chemistry of sodium and potassium thiocyanates is that of the thiocyanate anion (372—375). 

Active fractions are combined and concentrated in vacuo to about 5 liters. The concentrate is then adjusted to a pH of 8.0 with 6N sulfuric acid and passed through a column packed with 1 liter of an anion exchange resin, Dowex 1X2 (OH form). The column is washed with about 5 liters of water and the effluent and the washings containing active substance are combined and are concentrated to 1/15 by volume. The concentrate is adjusted to a pH of 10.5 with 6N sodium hydroxide and 5 volumes of acetone is added thereto. The resultant precipitate is removed by filtration and the filtrate is concentrated to 500 ml. The concentrate is adjusted to a pH of 4.5 with 6N sulfuric acid and 2.5 liters of methanol is added thereto. After cooling, a white precipitate Is obtained. The precipitate is separated by filtration and washed with methanol. After drying in vacuo, about 300 g of white powder is obtained. 

The choice of the anion ultimately intended to be an element of the ionic liquid is of particular importance. Perhaps more than any other single factor, it appears that the anion of the ionic liquid exercises a significant degree of control over the molecular solvents (water, ether, etc.) with which the IL will form two-phase systems. Nitrate salts, for example, are typically water-miscible while those of hexaflu-orophosphate are not those of tetrafluoroborate may or may not be, depending on the nature of the cation. Certain anions such as hexafluorophosphate are subject to hydrolysis at higher temperatures, while those such as bis(trifluoromethane)sulfonamide are not, but are extremely expensive. Additionally, the cation of the salt used to perform any anion metathesis is important. While salts of potassium, sodium, and silver are routinely used for this purpose, the use of ammonium salts in acetone is frequently the most convenient and least expensive approach. 

Theory. Conventional anion and cation exchange resins appear to be of limited use for concentrating trace metals from saline solutions such as sea water. The introduction of chelating resins, particularly those based on iminodiacetic acid, makes it possible to concentrate trace metals from brine solutions and separate them from the major components of the solution. Thus the elements cadmium, copper, cobalt, nickel and zinc are selectively retained by the resin Chelex-100 and can be recovered subsequently for determination by atomic absorption spectrophotometry.45 To enhance the sensitivity of the AAS procedure the eluate is evaporated to dryness and the residue dissolved in 90 per cent aqueous acetone. The use of the chelating resin offers the advantage over concentration by solvent extraction that, in principle, there is no limit to the volume of sample which can be used. 

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