Dimethylformamide, chemical structures

Solid state oxidation, both of the a- and the 3-phase [8] of dihydroquinacridone, affords crude a-quinacridone. Subsequent milling with salt in the presence of dimethylformamide produces the 7-modification, while the 3-form evolves in the presence of xylene. Solution oxidation of dihydroquinacridone, possibly performed as air oxidation in the presence of 2-chloroanthraquinone [9], forms crude 3-quinacridone. Milling with xylene likewise affords 3-quinacridone pigment (see tables of chemical structures on p. 613). 

Figure 1 gives a typical infrared spectrum of lake humic acid. The interpretation of infrared spectra of humic substances is discussed in depth by -MacCarthy and Rice in Chapter 21. The similarity of infrared spectra of humic acids from different lakes suggests a similarity of the aspects of chemical structure that are related to their infrared absorptions. However, infrared spectroscopy is not sensitive enough to uncover minor structural differences among humic acids. In fact, humic acids were separated by organic solvents (chloroform, methylethylketone, methanol, dimethylformamide) into various fractions (Ishiwatari, 1969b, 1973). Infrared spectra of two of these fractions, the chloroform-soluble fraction and the methylethylketone-... 

Six diamic acid additives were prepared by reacting 0.10 mol dianhydride with 0.20 mol aniline (An) or 0.10 mol diamine with 0.20 mol phthalic anhydride (PA) in a solvent mixture of one or more of N,N-dimethylformamide, N-methylpyrrolidinone and diglyme(2) at room temperature. The additives were precipitated into water. The chemical structures of the additives are shown in Figure 2. 

For details of polystyrene and polyDMA (polydimethylacrylamide) see Refs. [7, 12] respectively. Copoly(DMA-styrene) was obtained from the activated copolymer sampte 8c (see Table 6) TOL=toluene, EAC=ethyl acetate, THF=trtrahydrofuran, DCM=dichloromethane, DMF =dimethylformamide, DMSO=dimethylsulfo3dde, MeOH=methanoJ, AcOH = acetic acid Polymers with higher, or lower, expanded volumes can be obtained readily for all three polymer types [7, 12], but the pattern of polymer swelling in different solvents is a consequence of the chemical structure of the polymer... 

Figure 40 Gas storage in coordination polymers, (a) Chemical structures of the dicopper(II) paddlewheel secondary building block and 5,5 -(9,10-an racene yl)diisophthalate tetra-anion in the structure of the [/xg-5,5 -(9,10-anthracenediyl)diisophthalato]-diaqua-dicopper(n) dimethylformamide solvate, and (b) representation of the honeycomb array with internal orthogonal bridges. The solvent molecules are not shown and the water-bound hydrogen atoms were not located in the original study.

DOM is derived from autochthonous sources such as phytoplankton and photosynthetic bacteria (16) at Big Soda Lake near Fallon, Nevada. This lake is alkaline (pH 9.7) and chemically stratified. It contains DOC concentrations as high as 60 mg/L and dissolved salt concentrations as high as 88,000 mg/ L (17). The DOM in this lake is colorless. The fulvic acid fraction was isolated by adsorption chromatography (Amberlite XAD-8 resin) (18) and by zeo-trophic distillation of water from N,N-dimethylformamide (19). Average molecular model synthesis was achieved in a manner similar to that used for fulvic acid from the Suwannee River. The characterization data are presented in Table I and the structural model is presented in Structure 2. 

When chemical crosslinking by glycol-dimethacrylate is present, the chain fixation also remains in dimethylformamide, and optical anisotropy is retained. All these results show that chain entanglement plays a predominant role in the structure of PC-polymers. 

A,A-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), will form complexes with the tin, breaking the polymeric structure of the dioxastannolane but maintaining a coordination number of greater than four at the metal. A m-R2Sn02L structure has been proposed on the basis of 119Sn chemical shifts (—137 to —189 ppm) and Mbssbauer data (A 2.11-2.82 mm/second). The donor ligand is readily lost under reduced pressure (224). 

Although it has been suggested that some of the reactions of 2-ami-noimidazole can best be explained by its existence as the imino tautomer in dimethylformamide, this result was based on incorrectly interpreted chemical evidence. In fact, a UV study of 2-amino-l-methyl-4,5-di-phenylimidazole provides convincing evidence for the amino form with Kj = 3 X 10". Calculations of heats of combustion show that in the 4-aminoimidazole 5-aminoimidazole equilibrium there is a slight predominance of the 4-amino form [a conclusion which is inconsistent with Charton s hypothesis since (7m(NH2) = —0.161]. The compounds, however, exist as amino rather than imino structures. ... 

The structure, lividomycin 5"-phosphate, was furthermore proved by chemical synthesis. Penta-N-(benzyloxycarbonyl) lividomycin A was prepared from lividomycin A by the usual Schotten-Baumann procedure in a yield of 95% it had m.p. 135-150° (dec.). Acetonation with 2,2-dimethoxypropane in N,N-dimethylformamide in the presence of p-toluenesulfonic acid at 110° for 4 hours afforded the tri-O-isopropylidene derivative of N-(benzyloxycarbonyl)lividomycin A in 49% yield m.p. 129-133° (dec.). Phosphorylation of the sole primary hydroxyl group in the D-ribose moiety of -(benzyloxycarbonyl) lividomycin A with diphenyl phosphorochloridate in dry pyridine gave penta-N-(benzyloxy-... 

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