Methanol-ammonia mixed solvent

Absorption spectra of 2-nitroanisole in supercritical C02, N20, Freon-13, ammonia and C02-methanol mixtures were obtained on a Cary model 1605 spectrophotometer operated in the dual beam mode. The gases used as supercritical solvents were of the highest purity available from the supplier (Matheson) and were further filtered prior to use. The mixed solvent system of C02-methanol was obtained from Scott Speciality Gases (15.4 wt% methanol), and other mixtures were made in the laboratory. Spectra of 2-nitroanisole in n-pentane, methanol, tetrahydrofuran and acetonitrile (Burdick A Jackson) were obtained using quartz cells with a 1-cm light path and with a pure solvent blank in the reference beam. Vapor phase and supercritical fluid spectra were obtained using an air reference. 

Fig. 2. Relative scale of the Tc of the main HTSC groups and solidification points of different mixed solvents chloroethane + butyronitrile (I), n-pentane + methylcyclohexane + n-propanol (II), bromo-ethane + butyronitrile + isopentane + methylcyclopentane (III), chloromethane + dimethyl ether (IV), bromoethane + butyronitrile (V), propionitrile + butyronitrile (VI), methanol + dichloromethane (VII), ammonia + isopropanol + dimethylformamide (VIII). Data are taken from [28, 152].

In this case, the TLC system most commonly employed uses silica gel plates and a mobile phase of ethyl acetate/methanol/25% ammonia (85 10 5, by volume). The plates are prepared and the chromatogram developed in the standard way. After development, the plate is removed from the mobile phase, the solvent front marked, and the plate dried. Visualization of barbiturates is best achieved by the use of a mercuric chloride-diphenylcarbazone reagent. The latter is prepared as two component solutions, i.e. (i) 0.1 g of diphenylcarbazone in 50 ml of methanol, and (ii) 0.1 g of mercuric chloride in 50 ml of ethanol. These solutions should be freshly prepared and mixed just before use. The presence of barbiturates will give rise to blue-violet spots on a pink background when using this reagent system. 

Stability of 2,6-Bis(trichloromethyl) pyridine (XXVI) toward Nucleophilic Substitution. The colorless solution containing 6.2 grams (0.02 mole) of XXVI in 25 ml. of DMF was heated for 2 hours at 165° C., during which time gaseous ammonia was passed in. When, after cooling, the reaction mixture was stripped of solvent under vacuum, a white, crystalline solid remained. Recrystallized from a methanol-water mixture, the substance had a melting point of 86-87° C. which was not depressed when mixed with an authentic sample (XXVI) (7, 9). The recovery of XXVI was quantitative. 

The first step is the formation of H-bonded intermediate 49, in which Ccarbene takes on substantial cationic character. Next, termolecular attack by the amine in the presence of Y provides tetrahedral intermediate 50, which then breaks down into products. The reaction is sensitive to steric hindrance, with ammonia and primary amines reacting rapidly (several orders of magnitude faster than aminolysis of carboxylic acid esters) and secondary amines reacting much more sluggishly. The actual kinetic order associated with the amine is also a function of the solvent. Aprotic solvents such as hexane require a rate law with a third-order contribution from the amine pro tic solvents such as methanol show a mixed first- and second-order contribution from the amine. 

A methyl substituted aromatic compound such as p-cresol can be best converted to the corresponding aldehyde such as p-hydroxy benzaldehyde by reacting a methanolic alkaline p-cresol in presence of a mixed co-acetate-Mn-acetate catalyst at a pressure of 8-lOkg/cm and temperature of 75-100°C in presence of air and a solvent such as piperidine or an amine (ammonia, triethylamine, etc.) that would yield approximately 80-90% of the aldehyde in about 16-18 hr. 

In most of the investigations mentioned so far in this section involving solvent mixtures it is likely that the primary solvation shell does not vary with solvent composition. However, there are occasions when variation of reactivity with solvent mixture composition is attributed to changes in primary solvation shell composition, as in the case of reaction of Ni + with ammonia in aqueous methanol. In the reaction of Be + with sulphate in aqueous DMSO, there is strong n.m.r. evidence for variation in primary solvation shell composition. In the reaction of Co with tetraphenylporphine in acetic acid-water the kinetics also reflect the presence of varying amounts of mixed solvates. By way of contrast, in reactions of copper(ii) with polythiaethers in methanol-water mixtures only Cuaq + reacts mixed solvates are claimed to be of negligible reactivity. In the reaction of chromium(iii) with edta in methanol- and ethanol-water mixtures, variation in pK for the Cr + has an effect on the formation rates, but the individual rate constants for the reactions of Cr + and of CrOH + with the ligand seem to be practically independent of solvent composition. ... 

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