The Diethylamine-Water System

Parameter Values Standard Deviation Covariance Objective Function 

Copp and Everet (1953) have presented 33 experimental VLE data points at three temperatures. The diethylamine-water system demonstrates the problem that may arise when using the simplified constrained least squares estimation due to inadequate number of data. In such case there is a need to interpolate the data points and to perform the minimization subject to constraint of Equation 14.28 instead of Equation 14.26 (Englezos and Kalogerakis, 1993). First, unconstrained LS estimation was performed by using the objective function defined by Equation 14.23. The parameter values together with their standard deviations that were obtained are shown in Table 14.5. The covariances are also given in the table. The other parameter values are zero. 

Hgure 14.5 The minima of the stability function at the experimental temperatures for the diethylamine-water system [reprinted from Computers Chemical Engineering with permission from Elsevier Science]. 

Therefore, although the stability function was found to be positive at all the experimental conditions it becomes negative at mole fractions between 0 and the first measured data point. Obviously, if there were additional data available in this region, the simplified constrained LS method that was followed above would have yielded interaction parameters that do not result in prediction of false liquid phase splitting. 

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Table 14.5 Parameter Estimates for the Diethylamine-Water System...

Note The following solvent systems were tried but gave no separation dioxane/water (7 3, v/v) n-butanol saturated with water amyl alcohol/ace-tone/water/benzyl amine (40 35 20 5, v/v) 2,6-lutidine/water/ethnol/diethylamine (55 25 20 1, v/v). 

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. 

Fig. 16.10. Phase diagram at constant pressure of the system diethylamine + water...

Figure 8.4. Water and diethylamine have both hydrogen bond donor and acceptor properties through the -OH or = NH groups. They cross-link through hydrogen bonds and can withstand considerable capillary tension. Pyridine has only hydrogen bond acceptor properties and cannot cross-link with itself. Pyridine cannot withstand large capillary forces the energy storage capacity of the pyridine-saturated system is small (Thomas and Krmgstad, 1971).

The deprotection of aloe derivatives of secondary amines such as N,N-benzylme-thylamine under the above conditions gave a substantial amount of the undesired allylamine [32], However, the use of a 40-fold excess of diethylamine as the jr-allyl scavenger led to the desired benzylmethylamine in quite good yield (Eq. 9). The formation of the undesired allylamine was also suppressed using a fivefold excess of diethylamine in a butyronitrile/water system. N-Allyloxycarbamates derived from secondary amines, such as morpholine, piperidine, proline, and ephedrine, reacted under the above-mentioned conditions at room temperature within 15 min to give the parent amines in quantitative yields without formation of the undesired allylamine. 

When the N-alloc protecting group of primary amines such as benzylamine is cleaved rapidly imder these standard conditions in quantitative yields, the use of a 40-fold excess of diethylamine as the 7t-allyl scavenger or a five-fold excess of diethylamine in a butyronitrile/water system is necessary for the quantitative deprotection of aUoc derivatives of secondary amines. 

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

The observed rates of transfer are lower than those calculated by the correlation of Eq. 26 for organic molecules which themselves are surface-active, without specifically added long-chain molecules thus in the transference of (C4H9)4NI from water to nitrobenzene, of benzoic acid from toluene to water and the reverse, of diethylamine between butyl acetate and water, of n-butanol from water to benzene, and of propionic acid between toluene and water, the rates (44, 4 ) are of the order one-quarter to one-half those calculated by Eqs. (25) and (26). Since with these systems the solute itself is interfacially active, and therefore its monolayers should reduce the transfer of momentum, we interpret these findings as indicative that Ri and R2 are increased in this way. This is... 

The solvent systems benzene/ethyl acetate/diethylamine/methanol/ water (15 22 3 6 1, v/v) and benzene/ethyl acetate/diethylamine (5 5 1, v/v) containing 8% methanol were used to separate a number of analogs of colchicine, deacetylcolchicine, and their A/-formyl derivatives (33b). 

Surface water half-lives range from t/2 4-11 d in freshwater systems, t/2 = 0.1-10 d in cloud water, t,/2 > 1000 d in oceans for PCBs with as many as 8 chlorines for OH- oxidation (Sedlak Andren 1991) photodegradation t,/2 = (7.1 1.5) h in aqueous solution with the presence of diethylamine after exposure to simulated sunlight (Lin et al. 1995). 

A similar solvent system was also used by Rasmussen et al.51 for the analysis of morphine in organic poppy extracts (Fig. 7.13). The extracts could be analyzed without any purification prior to HPLC analysis. Gimet and Filloux performed analyses on alkaloids -including opium alkaloids - in pharmaceutical preparations, and used a microparticulate silica gel column and diethyl ether or diethyl ether saturated with water as mobile phase. In both cases 0.4% diethylamine was added to the mobile phase (Fig. 7.14). An increase... 

Fig.8.9). A similar system was applied by Gimet and Filloux for the analysis of various alkaloids in pharmaceutical preparations (Fig.7.14). It was found that an increased saturation of the diethyl ether with water led to reduced retention times a similar effect was found for the amount of diethylamine added to the solvent. For the separation of strychnos alkaloids, good results were also obtained with the mobile phase ethyl acetate - methanol -ammonia in combination with silica gel columns55 . ...

Tc when we cross the line — 4, we obtain a LCST. An example of the system with a LCST is a mixture of water and diethylamine, which has a critical temperature at about 143.5 °C. 

Subsequently, other workers including O Neill and Cole (4 and Dannenberg (5 ) showed that Reactions 2 and 3 proceed to the exclusion of Reaction 4. The reactivity of a particular epoxide-amine system depends on the influence of the steric and electronic factors associated with each of the reactants. It has been known for some time that hydroxyls play an important role in the epoxide-amine reaction. For example, Shechter et al. ( ) studied the reaction of diethylamine with phenylglycidyl ether in concentrated solutions. They showed that acetone and benzene decreased the rate of reaction in a manner consistent with the dilution of the reactants, but that solvents such as 2-propanol, water, and nitromethane accelerated the reaction (Figure 3). They also found that addition of 1 mol of phenol to this reaction accelerated it to an even greater extent that addition of 2-propanol or water. 

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