Systems, acetic acid-water benzene-toluene

No solvent system resolves all the Dns-amino acids by one-dimensional chromatography and, also, TD chromatography requires more than two runs for a complete resolution. The most common used eluents on polyamide layers are benzene-acetic acid (9 1), toluene-acetic acid (9 1), toluene-ethanol-acetic acid (17 1 2), water-formic acid (200 3), water-ethanol-ammonium hydroxide (17 2 1 and 14 15 1), ethylacetate - ethanol- ammonium hydroxide... 

Aromatic substrates studied in acetonitrile or acetic acid solutions were toluene, m-xylene, ethyl benzene cind mesitylene and the results are shown in Table I. For all the systems containing no or very little water, a zeroth order kinetic law in substrate concentration was obeyed. As the concentration of water present initially was successively increased, the order ultimately beceune disturbed cind finally a first-order law was estciblished. Figures 2 and 3 show the changeover in reaction order for the nitration of toluene in acetonitrile solution. 

Traces of thionyl chloride are removed by reevaporation after addition of dry benzene. The purity of the peptides can be checked by thin-layer chromatography on silica gel using two solvent systems (1) 1-butanol-acetic acid-water, 18 2 5 (v/v) and (2) toluene-pyridine-water, 80 10 1 (v/v). All preparations should give a single spot. 

In weaker acid systems, other reactions involving the triplet state supervene to the exclusion of dimerization. Photolysis of 85 in 3-3% sulfuric acid, 96-5% acetic acid, and 0-2% water gave as products tri-phenylmethane (93), 9-phenylfluorene (94), 6is-9-phenylfluorenyl peroxide (95) and benzophenone (96). When benzene was present, tetra-phenylmethane (97) was also formed in addition to the other products. When the triphenylmethyl cation is irradiated in 3-3% H2SO4, 80 1% HOAc, 16-4% toluene, and 0-2% H2O, the products observed were... 

In general, symmetrical oxo-squaraines having the same end-groups are synthesized by reacting squaric acid with two equivalents of quatemized indolenine, 2-methyl-substituted benzothiazole, benzoselenazole, pyridine, quinoline [39, 45, 46] (Fig. 4) in a mixture of 1-butanol - toluene or 1-butanol - benzene with azeotropic removal of water in presence [39, 45] or absence [47] of quinoline as a catalyst. Other reported solvent systems include 1-butanol - pyridine [48], 1-propanol - chlorobenzene, or a mixture of acetic acid with pyridine and acetic anhydride [49]. Low CH-acidic, heterocyclic compounds such as quatemized aryl-azoles and benzoxazole do not react, and the corresponding oxo-squaraines cannot be obtained using this method [23, 50]. 

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 increasing use of physical data in laboratory work has also led to developments in the technique of determining the dielectric constant. This constant is an especially useful quantity when the mixture contains water (diel. const. 80) or other components having widely different values. Examples are the mixtures acetic acid (diel. const 6.13)-acetic anhydride (22.2) and methanol-toluene. In the latter system the azeotroj)e has a dielectric constant of 26.8, whilst methanol and toluene have values of 33.8 and 2.37, respectively [65]. The dielectric constant has also proved convenient for determining toluene in benzene, in spite of the fact that the difference in the figures for these two com x>nents is only 0.08 units. 

ATRP can be performed in bulk, in solution, or in a heterogeneous system (e g., emulsion, suspension). Various solvents have been used for ATRP in solution for various monomers. These include benzene, toluene, acetone, ethyl acetate, anisole, diphenyl ether, dimethyl formamide, ethylene carbonate, alcohol, water, carbon dioxide, and many others (Matyjaszewski and Xia, 2001). The use of a solvent may become necessary when the polymer formed is insoluble in its monomer. The choice of a solvent is in uenced by several factors, such as chain transfer to solvent, interactions between solvent and the catalyst, catalyst poisoning by solvent (e.g., carboxylic acids and phos-... 

Systems 1 and 2, silica Gel (60 Fj54, 0.25 mm), benzene-ethyl acetate-formic acid (40 10 5) and toluene-ethyl formate-formic acid (50 40 10) 3, polyamid (DC-Alufolien F2M, 0.15 mm), toluene-butan-2-one-methanol (60 25 15) 4, reversed-Phase (C-I8 F254. 0.25 mm) methanol-formic acid-water 58 10 16). 

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