Sizing dimethylformamide

Type 4A sieves. A crystalline sodium aluminosilicate with a pore size of about 4 Angstroms, so that, besides water, ethane molecules (but not butane) can be adsorbed. This type of molecular sieves is suitable for drying chloroform, dichloromethane, diethyl ether, dimethylformamide, ethyl acetate, cyclohexane, benzene, toluene, xylene, pyridine and diisopropyl ether. It is also useful for low pressure air drying. The material is supplied as beads, pellets or powder. 

Mourey, T. H. and Bryan, T. G., Size-exclusion chromatography using mixed-bed columns with dimethylformamide at near-ambient conditions comparison of pStyragel HT Linear and PL Gel mixed-bed columns, /. Liquid Chromatogr., 14, 719, 1991. 

Tokuda, T., Mori, M., and Yamada, T., Size-exclusion chromatography on polyhydroxymethacrylate gel with dimethylformamide as eluent, /. Chromatogr. A, 722, 123, 1996. 

The requirements for solid-phase synthesis are diverse. The support must be insoluble, in the form of beads of sufficient size to allow quick removal of solvent by filtration, and stable to agitation and inert to all the chemistry and solvents employed. For continuous-flow systems, the beads also must be noncompressible. Reactions with functional groups on beads imply reaction on the inside of the beads as well as on the surface. Thus, it is imperative that there be easy diffusion of reagents inside the swollen beads and that the reaction sites be accessible. Accessibility is facilitated by a polymer matrix that is not dense and not highly functionalized. A matrix of defined constitution allows for better control of the chemistry. Easier reaction is favored by a spacer that separates the matrix from the reaction sites. Coupling requires an environment of intermediate polarity such as that provided by dichloromethane or dimethylformamide benzene is unsuitable as solvent. 

Hydroxylic solvents are capable of solvating anions through hydrogen bonding, and so halide mobilities are relatively low in alcohols, with chloride the least mobile. The mobility decreases observed for all the halides upon going up the homologous series of aliphatic alcohols may be the result of the increased size and mass of the alkyl group. A similar mass effect may be seen in the lowered mobility of the halides in dimethylacetamide compared to dimethylformamide. Here, as in the alcohol series, dipole moments and viscosities of the two solvents do not appear to be sufficiently different to explain the mobility differences. 

There occur marked differences between rodent species and humans in the proportions of a dose excreted as these various major metabolites, and the dose size introduces further variables. Mr et al. (1989) gave male Sprague-Dawley rats, BALB/c mice and Syrian hamsters 0.1,0.7 and 7 mmol/kg bw dimethylformamide (approximately 7,50 and 500 mg/kg bw) by intraperitoneal injection and collected urine for 60 h (rat), 24 h (mice) and 36 h (hamster). In all cases, dimethylfonnamide and AMCC were very minor urinary metabolites, while the amounts of substances analysed as W-methylformamide ... 

Bis[dimethylpropylsilylmethyl] Ditellurium5 An H-shapcd electrolytic cell with a ealholyte volume of 100 ml is fitted with a tellurium cathode (99.99% purity, 15-20 cm2 surface area) and a platinum-net anode. To the cathode compartment, separated from the anode by a ceramic diaphragm of 1.6 gm pore size, are added 100 ml of a 1 molar solution of dry sodium perchlorate in dimethylformamide and the catholyte is deaerated with argon. At a cathode potential of 1.4 V with respect to an aqueous saturated calomel electrode, 2500... 

Chlorophyll concentrations were estimated from 40 ml subsamples following Suzuki and Ishimaru (1990). Samples were filtered on Whatman GF/F glass-fibre filters (pore size 0.45 pm). Chlorophyllous pigments were extracted by direct immersion of the filters in 5 ml of N,N-dimethylformamide, and actual extractions were made in the dark at 20°C. Concentrations of chlorophyll a in the extracts were determined following Strickland and Parsons (1972) using a Turner 450 fluorometer previously calibrated with chlorophyll a extracted from Anacystis nidulans (Sigma Chemicals, St Louis). 

Preparation of Cellulose-Polystyrene Graft Copolymers. The polystyr-yl mono- and di-carbanions were prepared in THF at -78 °C by using n-butyl lithium and sodium naphthalene as the initiators, respectively. The carban-ions were reacted with dry carbon dioxide. The products were precipitated in methanol, filtered, washed with water and methanol, and dried. Size exclusion chromatography (SEC) established that the molecular weight of the polystyryl monocarboxylate was 6,200 and that of the polystyryl di-carboxylate 10,2000. The mono- and di-carboxylates were reacted with mesylated cellulose acetate in dimethylformamide at 75 °C for 20 h to give the cellulose-polystyrene graft copolymer (GP 1) and crosslinked cellulose-polystyrene graft copolymer (GP 2), respectively. 

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