Water lithium perchlorate

Isothermal vapor-liquid equilibrium data at 75°, 50° and 25° C for the system of 2-propanol-water-lithium perchlorate were obtained by using a modified Othmer still. In the 2-propanol-rich region 2-propanol was salted out from the aqueous solution by addition of lithium perchlorate, but in the water-rich region 2-propanol was salted in. It is suggested from the experimental data that the simple electrostatic theory cannot account for the salt effect parameter of this system. 

The isothermal vapor-liquid equilibrium data at 75°, 50°, and 25°C for the 2-propanol-water-lithium perchlorate system are listed in Tables I and II. It can be seen from these tables that in the alcohol-rich region the vapor phase composition of 2-propanol increases with an increase in salt concentration. However, in a mixed solvent of 10 mol % alcohol the change of the vapor phase composition is small, and at a temperature of 50° and 25°C it even decreases a... 

S-Substituted thiiranium ions react with water and alcohols to give trans ring opening (Scheme 72). A report that oxygen nucleophiles attack sulfur as well as carbon has been shown to be incorrect (79ACR282). The intermediate thiiranium ion (57) in the presence of lithium perchlorate readily yields the carbenium ion which undergoes a transannular hydride... 

Lithium perchlorate [7791-03-9] M 106.4, pK -2.4 to -3.1 (for HCIO4). Crystd from water or 50% aq MeOH. Rendered anhydrous by heating the trihydrate at 170-180° in an air oven. It can then be recrystd twice from acetonitrile and again dried under vacuum [Mohammad and Kosower J Am Chem Soc 93 2713 19711... 

A study of the Diels-Alder reaction was carried out by Earle et al. [42]. The rates and selectivities of reactions between ethyl acrylate (EA) and cyclopentadiene (CP) in water, 5 m lithium perchlorate in diethyl ether (5 m EPDE), and [BMIM][PE(3] were compared. The reactions in the ionic liquid [BMIM][PE(3] were marginally faster than in water, but both were slower than in 5 m EPDE [42, 43] (see Table 5.1-1 and Scheme 5.1-18). It should be noted that these three reactions give up to 98 % yields if left for 24 hours. The endo. exo selectivity in [BMIM][PE(3] was similar to that in 5 M EPDE, and considerably greater than that in water (Table 5.1-1). 

Whilst some organic compounds can be investigated in aqueous solution, it is frequently necessary to add an organic solvent to improve the solubility suitable water-miscible solvents include ethanol, methanol, ethane-1,2-diol, dioxan, acetonitrile and acetic (ethanoic) acid. In some cases a purely organic solvent must be used and anhydrous materials such as acetic acid, formamide and diethylamine have been employed suitable supporting electrolytes in these solvents include lithium perchlorate and tetra-alkylammonium salts R4NX (R = ethyl or butyl X = iodide or perchlorate). 

Grieco investigated the intramolecular Diels-Alder reaction of imi-nium ions in polar media such as 5.0 M lithium perchlorate-diethyl ether and in water129 to form carbocyclic arrays. They showed that water as the solvent provided good-to-excellent yields of tricyclic amines with excellent stereocontrol (Eq. 12.58). 

The Diels-Alder reaction is an important and widely used reaction in organic synthesis (Sauer and Sustmann, 1980), and in the chemical industry (Griffiths and Previdoli, 1993). Rate enhancement of this reaction has been achieved by the use of solvents such as water, surfactants, very high pressure, lithium amides, alkylammonium nitrate salts, and macrocyclic hosts (Sherman et ak, 1998). Diels-Alder reactions can be ran in neutral ionic liquids (such as 1-butyl-3-methylimidazolium trifluoromethanesulfo-nate, l-butyl-3-methylimidazolium hexafluorophophate, l-butyl-3-methylimidazolium tetrafluoroborate, and l-butyl-3-methylimidazolium lactate). Rate enhancements and selectivities are similar to those of reactions performed in lithium perchlorate-diethyl ether mixtures. 

According to A. Potilitzin, the melting point of trihydrated lithium perchlorate is 95° and, between 98° and 100°, the salt loses approximately two-thirds of its combined water and all the water is lost between 130° and 150° the anhydrous salt melts at 236°, and loses no oxygen at 300° this gas is evolved at about 368°, at 380° the speed of decomposition is rapid—lithium chlorate and chloride are first... 

The thermodynamic excess functions for the 2-propanol-water mixture and the effects of lithium chloride, lithium bromide, and calcium chloride on the phase equilibrium for this binary system have been studied in previous papers (2, 3). In this paper, the effects of lithium perchlorate on the vapor-liquid equilibrium at 75°, 50°, and 25°C for the 2-propanol-water system have been obtained by using a dynamic method with a modified Othmer still. This system was selected because lithium perchlorate may be more soluble in alcohol than in water (4). 

Materials. Distilled water was used 2-propanol and trihydrous lithium perchlorate, of guaranteed reagent quality from Wako Pure Chemicals Co., were used without further purification. The purity of the 2-propanol was checked by gas chromatography, with Porapak-Q as the column packing, and found to be more than 99.9 mol %. The physical properties of pure solvents were compared with the literature values in a previous paper (2), and the agreement was satisfactory. 

Equilibrium vapor condensate was analyzed by means of density measurement at 25.00° 0.02°C. An Ostwald pycnometer (capacity ca. 5 cm3) was used. Liquid phase composition was calculated by taking a material balance. In this case, the three moles of water present in trihydrous lithium perchlorate were considered water component. The accuracies of both compositions were 0.001 mole fraction. 

The salt effect parameter ko is plotted in Figure 2, and the data for lithium chloride and lithium bromide reported in the previous paper (3) are also plotted for the purposes of comparison. It can be seen from Figure 2 that ko depends markedly on the solvent composition. The values of ko decrease and in the extremely water-rich region k0 is negative at 50° and 25°C. In other words, 2-propanol is salted in by the addition of lithium perchlorate. The salting-in effect of 2-propanol increases with reduction in temperature. 

Heats of solution of lithium perchlorate in 20, 40, 60, 80, 90, and 100 wt % acetronitrile-water mixtures at 298.16°K are reported. The heats of dilution were measured for lithium perchlorate in the mixed solvent containing 90 wt % CH CN. The heats of transfer (AHtr) of lithium perchlorate from water to aqueous acetonitrile were calculated. The results are discussed in terms of the structure of the solvent system and selective solvation properties of the lithium ion. 

The purpose of this study is to examine the structural features of acetonitrile-water mixtures over the whole composition range using the heats of solution and dilution of lithium perchlorate as a probe. The effect of water on thermodynamic properties such as heats of solution is also of interest. 

Lithium perchlorate was purified as described earlier (6). Acetonitrile was Fisher ACS reagent grade and was used without further purification. Water was distilled twice, the second time in a Corning AG-2 all glass still, and had a specific conductivity at 25°C of 8 X 10 7 ohm-1 cm-1. The mixed solvents were prepared by weight as shortly as possible before heat measurements were made. 

Heats of solution for lithium perchlorate in pure water have been reported previously (8). The heats of transfer to the aqueous mixtures and anhydrous acetonitrile are given in Table IV and Figure 2. 

Table IV. Heats of Transfer of Lithium Perchlorate from Water to Aqueous Acetonitrile...

Figure 2. Heats of transfer — AH r of lithium perchlorate from water to aqueous acetonitrile at 298°K...

In accord with this assignment is the observation of Hudson and Moss144 that, with 95% aqueous acetone solvent, lithium perchlorate increased the rate of hydrolysis of 2,4,6-trimethylbenzoyl chloride, whereas chloride ions have no effect this is in contrast to the behaviour of 4-nitrobenzoyl chloride whose rate of hydrolysis is decreased by lithium perchlorate and increased by chloride ions. The influence of solvent sorting145 is probably small for SN1 reactions in 90% aqueous acetone and neglecting ion pairing an observed salt effect reflects the effect of the ion atmosphere on the transition state. The same observation will not hold for either dioxan/water (because of the low dielectric constant of dioxan) and acetone/water of high water content (because of the extensive solvent sorting). 

Fig. 15 HPLC of vitamins A, D3, and E in the unsaponifiable fraction of milk. Column, 5 /nm Spheri-5 RP-18 (220 X 4.6-mm ID) mobile phase, methanol/water (99 1) containing aqueous 0.1 M lithium perchlorate, 1 ml/min amperometric detection (oxidative mode), glassy carbon electrode, +1.05 V, vs silver-silver chloride reference electrode. Peaks (1) retinol (2) vitamin D3 (3) a-tocopherol. (Reprinted from Ref. 143 with the kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25,1055 KV Amsterdam, The Netherlands.)...

A qualitative and quantitative HPLC method for analysis of mixtures of 12 antioxidants was described Grosset et al. (121). For the identification of the components present, gradient elution with a convex profile from 35 65 water-methanol to pure methanol is used, on a Waters 5-/xm C18 column, with UV detector. Propyl gallate was not separated by this system. For quantitative analysis, with UV and electrochemical detectors in series, the water-methanol mixture or pure methanol was used as the eluent, under isocratic conditions, with lithium perchlorate as supporting electrolyte. An applied potential ranging from +0.8 to +1.7 V allows detection of all the antioxidants tested. Both modes of detection were very sensitive, with limits of detection as low as 61 pg. 

A study19 of the effect of added lithium perchlorate on the second-order rate coefficients for reaction (12) (R = Et, Pr", Bu") showed that all three substitutions, in solvent 96 % methanol-4 % water, were subject to marked positive kinetic salt effects. The effects were analysed in terms of the Bronsted-Bjerrum equation... 

Fig. 2. The effect of lithium perchlorate on the molar activity coefficients of reactants and transition states in the bimolecular substitution of tetraalkyltins by mercuric iodide in solvent 96 % methanol-4 % water. LiC104 = LiC104 (estimated) But = Bu 4Sn/HgI2 transition state Prt = Pr"4Sn/HgI2 transition state Ett = Et4Sn/HgI2 transition state Et = Et4Sn Hg = Hgl2 b = Pr"4Sn a = Bu"4Sn (IX)t — transition state (IX), see text.

Salt effects on reaction (42) (R = Me, X = Br) were also studied using the solvents dioxan (9) water(l), dioxan (4) water(l), and acetone. In all three cases it was shown that added bromide ion strongly depressed the rate and hence that the species HgBr3 was inoperative as an electrophile44. The effect of added lithium perchlorate was also investigated, but at the low concentrations used (0.09 x 10-4 M to 3.25 x 10-4 M) no salt effect could be observed. 

The effect of lithium perchlorate on the rate of reaction (44) (R = Me, X = Br) in solvent dimethylsulphoxide is unfortunately within experimental error, so that a calculation on the above lines would be meaningless. Since, however, mechanism SE2(open) is in force when dioxan(4) water(l), of e25 = 10.5, is the solvent, it would not be unreasonable if a similar mechanism applied also to reaction (44) (R = Me, X = Br) when dimethylsulphoxide, of 25 = 46.5, is the solvent. 

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