Dimethyl formamide , molecular

The intrinsic viscosity of poly(7-benzyl-L-glutamate) (Mq = 219) shows such a strong molecular weight dependence in dimethyl formamide that the polymer was suspected to exist as a helix which approximates a prolate ellipsoid of revolution in its hydrodynamic behaviorf ... 

Intrinsic Viscosity Measurements were made by standard techniques in dimethyl formamide (DMF) at 30 C. Weight average molecular weights were calculated from the following relationship ... 

The hydroboration/oxidation sequence does not change the molecular-weight distribution. Gel permeation chromatography (GPC) measurements in dimethyl-formamide (DMF) with the resulting polystyrene-ft-polyalcohol polymers show very similar polydispersity indexes (Table 10.2). Here, the hydroboration/oxidation sequence is clearly superior to the epoxidation reaction, which leads to a... 

Materials. Reagent grade solvents, dimethyl formamide (DMF), dimethyl acetamide (DMAC), dimethyl sulfoxide (DMSO) and methanol were purchased from Baker, stored over molecular sieves once opened, and used without further purification. Aminoethane thiosulfuric acid (AETSA) purchased from Kodak, and Taurine, purchased from Alfa were purified by recrystallization. Each was thrice recrystallized from hot, deionized water. The crystalline precipitate was dried (48 hours at 40 °C) in-vacuo and subsequently stored in a desiccator. Benzophenone (BP) was purchased from Aldrich Chemical Company. QUANTACURE BTC (BTC), (4-benzolybenzyl) trimethylammonium chloride, was used as supplied by Aceto, Inc., Flushing, New York. Phenyl glycidyl ether (PGE) was purchased from MCB, distilled in-vacuo. and stored at -15 °C. Epon 828 was used as supplied bv Shell Chemical Company. The epoxy equivalent weight (EEW) for Epon 828 determined by an appropriate titration, was found to be 187.7. 

Fig. 6 Wave-like ribbon structure of complex 18.p-xylene.l.5(DMF), where DMF=dimethyl-formamide. Guest p-xylene occupies the cavitand molecular cavity, while disordered DMF (only one position shown) occupies the cage created by pendant arms at the lower rim [39]... 

Both sulfonyl chloride and isothiocyanate will hydrolyze in aqueous conditions therefore, the solutions should be made freshly for each labeling reaction. Absolute ethanol or dimethyl formamide (best grade available, stored in the presence of molecular sieve to remove water) should be used to dissolve the reagent. The hydrolysis reaction is more pronounced in dilute protein solution and can be minimized by using a more concentrated protein solution. Caution DMSO should not be used with sulfonyl chlorides, because it reacts with them. 

The total quantum yield [4>cs(total)] for CS is decreased to 0.17 in dimethyl-formamide (DMF) due to the competition of the CSH from Fc-ZnP-H2F+-C6o (1.63 eV) to Fc-ZnP- -HzP-Cso (1.34 eV) versus the decay of Fc-ZnP-Fl2P -C6o to the triplet states of the freebase porphyrin (1.40 eV) and the Ceo (1.50 eV) [47]. In contrast to the case of most donor-acceptor-linked systems, the decay dynamics of the charge-separated radical pair (Fc -ZnP-H2P-C6o ) does not obey first-order kinetics, but, instead, obeys second-order kinetics [47]. This indicates that the mframolecular electron transfer in Fc -ZnP-H2P-C6o" is too slow to compete with the diffusion-limited inter-molecular electron transfer in solution. 

Molecular Weight of Grafted Side Chains. In previous work the wool had been hydrolyzed away from the grafted material in order to isolate the polystyrene side chains. Sodium hydroxide was used with good results however, about one-half of the polystyrene was soluble in only such solvents as dimethyl formamide and benzene-methanol mixtures. Infrared examination showed the presence of groupings charac-... 

Peptides extracted from casein with N, N-dimethyl formamide have complex electrophoretic patterns identical to those of the fraction first prepared by Long and co-workers and called X-casein (El-Negoumy 1973). These peptides are identical electrophoretically to those released by the action of plasmin, which is present in fresh raw milk, upon asr casein (Aimutis and Eigel 1982). Two of these peptides have tryptic peptide maps and molecular weights identical to those of a pair of the peptides produced by plasmin degradation of asl-casein. These peptides appear to be fragments of a8l-casein which are present in milk as the result of plasmin proteolysis. More definitive information on their primary structure is needed before nomenclature for these fragments can be established. 

Low molecular weight aromatic ethers have been prepared principally by the condensation of phenolate salts with aromatic halides 82). The Ullmann condensation (81), which employs copper or its salts as catalysts has been used in most cases in the laboratory. Recently a modification of the Ullmann condensation which consists of heating copper (1) oxide, the free phenol, and the aromatic halide in s-collidine has been reported (3). This method is recommended for alkali-sensitive aromatic compounds. In addition, reaction of phenolate salts with copper (1) oxide and the aromatic halide in boiling N,N-dimethyl formamide is described. When the halogen is activated by electronegative groups as in -chloroni-... 

Aprotic solvents, such as PC or AN, generally reveal a single relaxation process, with a more or less broad relaxation time distribution hiding the particular rotational diffusion processes around the molecular axes. Dimethyl formamide (DMF) represents a case where two of the particular processes sufficiently large difference in relaxation times Protic solvents show two (FjO, formamide FA) or three (alcohols ROH, N-methylformamide NMF) structural relaxation processes, each one with a characteristic relaxation time Eqs. 3 can be easily extended to this situation. 

Fig. 3. Intrinsic viscosity-molecular weight relationship of poly-7-benzyl-L-glutamates. The open circles represent the randomly coiled form and other symbols the a-helical form. The line of steeper slope is a plot of Simha s equation. Abbreviations dichloroacetic acid, DCA chloroform saturated with formamide, C-F dimethyl formamide, DMF light scattering, L.S. weight-average molecular weight, A/m. Reproduced from Doty et al. (1956).

J.M.E. Goldschmidt, JChemSoc 1956, 401-04- CA 50, 6189(1956) (Spectrophotometric study of HNDPhA. Molecular forms in dioxane) 3) W. Selig, US AtomEnerg Comm UCLR-6903 (1962), 13pp CA 57, 11861(1962) (Spectrophotometric detn in N,N-dimethyl-formamide) 4) J. Hansson A. Aim, JChromatog 9, 385-87(1962) (French) CA 58, 10034-35 (1963) (Thin-layer chromatography applied to analysis of expls) 5) F. Barbulescu et al. 

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