Dimethylformamide liquid structure

Fujii K, Kumai T, Takamuku T, Umebayashi Y, Ishiguro S (2006) Liquid structure and prefer-entieil solvation of metal ions in solvent mixtures of N, N-dimethylformamide and N-methylformamide. J Phys Chem A 110 1798-1804... 

From a structural point of view the OPLS results for liquids have also shown to be in accord with available experimental data, including vibrational spectroscopy and diffraction data on, for Instance, formamide, dimethylformamide, methanol, ethanol, 1-propanol, 2-methyl-2-propanol, methane, ethane and neopentane. The hydrogen bonding in alcohols, thiols and amides is well represented by the OPLS potential functions. The average root-mean-square deviation from the X-ray structures of the crystals for four cyclic hexapeptides and a cyclic pentapeptide optimized with the OPLS/AMBER model, was only 0.17 A for the atomic positions and 3% for the unit cell volumes. 

Abbreviations DCM, dichloromethane DIC, 1,3-diisopropylcarbodiimide DIEA, diiso-propylethylamine DMAP, 4-dimethylaminopyridine DMF, IVJV-dimethylformamide ELSD, evaporative light scattering detection HOBt, hydroxybenzotriazole IR, infrared LC/MS, high-pressure liquid chromatography/mass spectrometry NMM, V-methylmorpho-line NMR, nuclear magnetic resonance PyBop, benzotriazol-l-yloxytripyrrolidino-phosphonium hexafluorophosphate SAR, structure-activity relationship TFP, tetrafluorophenol THF, tetrahydrofuran. 

The fact that the structure of a solid monomer influences its polymerization substantially now seems obvious. It is not as clear whether structural phenomena can effect polymerization if the monomer is a liquid. It has long been known that ordered regions or clusters exist in liquids, and several years ago it was assumed that in some cases these regions in liquid monomers can influence the polymerization. One of the most vivid examples—namely, polymerization in the liquid-crystalline state—was accomplished by Krentzel and co-workers (I, 2, 3). The object of their study was p-methacrylylhydroxybenzoic acid, which forms conventional crystals in the pure state and does not polymerize in the solid state. However, when mixed with alkoxybenzoic acid, it forms liquid crystals of both smectic and nematic forms. Polymerization of p-meth-acryllylhydroxybenzoic acid in various forms of liquid crystals was compared with polymerization of the same substance dissolved in dioxane and dimethylformamide (DMF). 

It should be emphasized that the parameters involved in the activity coefficients are adjustable parameters which cannot be obtained easily from the properties of the mixed solvents, for instance the vapor-liquid equilibria. However, for the solubilities of structurally related caffeine and theophyllene in water/iV,iV-dimethylformamide, the values of the Wilson parameters are close to each other (1.96 and 0.12 for caffeine and 1.81 and 0.10 for theophyllene). If the Wilson parameters for theophyllene are used to predict the solubility of caffeine in water/iV,A -dimethylformamide, a deviation of 8.8% from experimental data is obtained. The deviation was, however, 6.5% when the Wilson parameters were determined by fitting the experimental solubility data (Table 1). The values of the Wilson parameters determined from the solubilities of the structurally more different sulfonamides (sulfadiazine, sulfadimidine, sulfamethizole, sulfamethoxazole, sulfapyridine, sulfamethoxypyridazine, sulfanilamide and sulfisomi-dine) in water/dioxane mixtures are listed in Table 3. Even for such cases, the average values of the Wilson parameters can be used for a first estimation of the solubilities of the above group of drugs (Table 3). 

Dimethylformamide (DMF) has a much more complex structure than either acetonitrile or acetone, but it is interesting to compare its infrared spectrum with that of formamide. By replacing the two acidic protons on the amino group by methyl groups, one obtains an aprotic liquid. As can be seen by comparing figs 5.16 and 5.19, the infrared spectrum of DMF is much simpler than that of for-... 

James et al have investigated the mechanochemical preparation of MOF by grinding 1,4-benzenedicarboxyhc acid (H2bdc) with ZnO or basic zinc carbonate [ZnC03]2-[Zn(OH)2]3 in a ball mill for 20 min, in the presence of a small amount of liquid the nature of the liquid determined the product [Zn(bdc)(H20>2] was obtained with water, [Zn(bdc)(H20)]DMF with DMF (dimethylformamide), and [Zn(bdc)(H20)] with methanol (Figure 5). These structures also show a different connectivity and they form one-, two-, and three-dimensional networks, respectively. Solid-state and NMR also confirmed the syntheses to be quantitative. 

The aim of this chapter also is the introduction of the photo physical study of model system ( 3-carotene in RTILs) mimicking very well spectroscopic data of this photosynthetic pigment in situ in the photosynthetic system Unique fluorescence properties of P-carotene in room temperature ionic liquids (RTIL) (Bialek-Bylka et al., 2007) and new (P-carotene) electronic states (3Ag- and 1B -) of both impxjrtant in photosynthesis isomers all-frans and 15-cis in ionic liquid with dimethylformamide (DMF) were found (Bialek-Bylka et al., 2008) and also a sensor detecting the methoxy group in the cation part of imidazolium ionic liquid was developed by us (Pawlak et al., 2009). In order to determine a detailed answer to the unique fluorescence properties, aroimd 100 times higher fluorescence yield of P-carotene in (ILl) (l-methyl-3-octyloxymethylimidazolium tetrafluoroborate) than in standard solvent n-hexane, the designed structures of RTILs were synthesized and carefully purified 1-methyl-3-octyloxymethylimidazolium tetrafluoroborate (ILl), l-methyl-3-... 

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