AA-Dimethylformamide

Quinoxaline-2,3-dithione (2,3-dimercaptoquinoxaline) (90) forms chelates with several transition elements and is used as a colorimetric agent for the detection and quantitative estimation of nickeT and also for the quantitative estimation of palladium. " Nickel gives a pink coloration with (90) in ammoniacal solution, and palladium an orange-red color in AA-dimethylformamide solution containing a little hydrochloric acid. Spectrophotometric studies of the chelate compounds of (90) with Ni(II), Co(II), and Pd(II) in alkaline solu-... 

Another decarboxylation reaction that employs lead tetraacetate under milder conditions, has been introduced by Grob et al7 In that case A-chlorosuccinimide is used as chlorinating agent and a mixture of AA -dimethylformamide and acetic acid as solvent. 

Equations for the KBIs in ternary mixtures are available in matrix form [2]. Explicit equations are obtained here which will allow us to analyze interesting features of ternary mixtures, such as the effect of a third component on the phase behavior of a binary mixture and the effect of a cosolvent (entrainer) on supercritical binary mixtures. Only the former problem is examined in the present paper. The calculations will he carried out for an interesting ternary mixture, namely AA -dimethylformamide-methanol-water, in order to extract information about the intermolecular interactions. In the next section explicit equations for the KB integrals will he derived and applied to the above ternary mixture. Finally, the results obtained will be used to shed some light on the local structure and the intermolecular interactions in the above mixture. 

In chemical terms a typical exchange process of the type considered is the hindered internal rotation problem in AA-dimethylformamide (Gutowsky and Holm, 1956). 

The features described above may be seen in the proton resonance spectrum of AA-dimethylformamide for the methyl protons. In this particular case the chemical shift difference is only 6 c.p.s. at 30 Mc/s and this illustrates the limitations of studying line widths of the separated resonances because overlap and coalescence of the two signals occurs over a very limited region of lifetimes. The techniques applied in such a case to obtain lifetimes from a steady state spectrum are the following ... 

Pol5miers of 1-vinyl-1,2,4-triazole are nontoxic, have a high hydrophiUc-ity, and a high hydrolysis stabiUty. Possible applications are in the food industry and medicine. Copolymers with of 2-hydroxyethyl methacrylate (HEMA) are used in biological and medical applications. They can be prepared in ethanol and AA -dimethylformamide (DMF) in the presence of 2,2 -azobisisobutyronitrile (AIBN) as the initiator. 

Solubility Soluble in water, AA -dimethylformamide UV-Visible (Xmax) 492 mn Melting Point >250°C... 

Cellulose can be converted into a hemiacetal derivative, methylol cellulose , by reacting with formaldehyde in methyl sulphoxide. Other aprotic solvents, such as pyridine, AA-dimethylformamide, AA-dimethylacetamide, A-methyl-2-pyrrolidinone, and thiolane-1-oxide can be substituted for methylsulphoxide for this conversion. More concentrated solutions of methylol cellulose could be obtained when cellulose and paraformaldehyde were heated together in the solvent than when formaldehyde gas was bubbled through a suspension of cellulose in the solvent. Solutions of 10% cellulose in methylsulphoxide could be obtained by this method. During the swelling of cellulose in ethanolamine, ethylenediamine, and methyl sulphoxide, the solvent retention capacity of cellulose at 20—120°C decreased by 10—20%, depending on the solvent."... 

The Rm values obtained in different solvent systems are similar for acetone or methanol aqueous mobile phases, but for AA -dimethylformamide, they are significantly lower. This observation can be explained by the structure of AA -dimethylformamide, which is very different from water. 

A tertiary amide has no hydrogens on the nitrogen. Substituents on the nitrogen are listed alphabetically together with the other substituents from the carboxylic acid portion of the chain. As usual, the smaller members of the class have retained their common names, which are based on the common names for the smaller carboxylic acids. For example, you will often encounter AA -dimethylformamide (abbreviated DMF) because it is a usefiil polar, high-boiling solvent. 

UV-Vis absorption spectra were recorded on a JASCO V-550 spectrometer. Emission spectra of the lanthanide complexes were measured with a JASCO F-6300-H spectrometer and corrected for the response of the detector system. The intrinsic emission quantum yields (< n) of lanthanide complex solutions degassed with an argon (10 ttiM in toluene, chloroform, acetone, AA -dimethylformamide DMF) were obtained by comparison with the integrated emission signal... 

The ionic conductivity in the wet state of phosphorylated chitosan membranes prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in AA -dimethylformamide was investigated by Wan et alP The authors observed that similarly to unmodified chitosan membranes phosphorylated chitosan membranes are hardly conductive in their dry states with conductivities between 10" and 10 S/cm. The entire conduction process occurs after the water incorporation increases the ionic conductivity values up to 10 and 10 S/cm depending on the phosphorus content in the sample. The best result of 1.2 x 10" S/cm was obtained with the sample containing 87.31 mg/m of phosphorus content. They also observed that the increase in the phosphorus content promotes a decrease in the crystallinity of phosphorylated chitosan membranes, an increase in the swelling index and not a significant loss of their tensile strength and thermal stability in comparison with the unmodified chitosan membranes. 

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