Formamide solutions

Simha equation), where a/b is the length/diameter ratio of these cigarshaped particles. Doty et al.t measure the intrinsic viscosity of poly(7-benzyl glutamate) in a chloroform-formamide solution and obtained (approximately) the following results ... 

Thermoplastic xylan derivatives have been prepared by in-hne modification with propylene oxide of the xylan present in the alkaline extract of barley husks [424,425]. Following peracetylation of the hydroxypropylated xylan in formamide solution yielded the water-insoluble acetoxypropyl xylan. The thermal properties of the derivative quahfy this material as a potential biodegradable and thermoplastic additive to melt-processed plastics. Xylan from oat spelts was oxidized to 2,3-dicarboxyhc derivatives in a two-step procedure using HI04/NaC102 as oxidants [426]. 

Nickel and Weber [30] reported aqueous titrations of carboxylic acids, phenols, acidic drugs containing NH groups, cationic acids (ammonium salts) in dimethyl-formamide solution against 0.1 M potassium hydroxide aqueous solution as the... 

Figure 5. SEM of the cross-section of a SPSF-Na (0.42) membrane cast from 70 30 THF-formamide solution, dried for 200 s, and gelled in IP A...

Fig. 5.10 Current-time behavior during 20 V potentiostatic anodization of a Ti foil (99.8 % pure) in a formamide solution containing 5% H2O and identical molar concentrations (0.27M) of fluoride ion bearing compounds with four different cationic species Hydrogen (H ), Ammonium (NH4 ), Tetrabutylammonium ([C4Hg]4N ), and Benzyltrimethylammonium...

Double-layer properties in aqueous, propylene carbonate and formamide solutions have been studied at room temperature for liquid Ga-Pb alloy (0.06 atom % of Pb) [15], as a model of Pb electrode with renewable surface. The electrode behaves as an ideally polarizable electrode in a wide potential range, and its capacitance is intermediate between that of Ga and Hg electrodes and is independent of the solvent. This electrode is much less lipophilic than Ga. Adsorption of anions on this electrode increases in the sequence -BP4 = S042 < Gl < Br < r. 

Funt and Williams reported that the copolymer compositions of methyl methacrylate and acrylonitrile varied at the same electrode depending upon the salts used in the saturated dimethyl formamide solution (Table 5) (19). They believed in the simultaneous occurrence of free radical and ionic polymerization in the system. Yield of polymers also differed with a variety of salts in the polymerization of methyl methacrylate in dimethyl sulfoxide (<5). Nevertheless no pattern of correlation has been given on the aspects relating to the supporting electrolytes. 

Another interesting reaction of diamines with isothiocyanates is the formation of l,3,5-triazepine-2-thione derivatives by the action of various classes of diamines on 2,3,4,5,6-penta-O-acetyl-D-gluconyl isothiocyanate (32). The reaction has been performed in acetonitrile or N,N-dimethyl-formamide solution with o-phenylenediamine, diaminomalononitrile, 5,6-diamino-l,3-dimethyluracil, 4,5-diamino-2,6-dithiopyrimidine, 4,5-diamino-2-thiopyrimidine, and 4,5-diaminopyrimidine, and afforded... 

Band A is assigned to coordinated cyanide. The bands at 2040, 2008, and 1970 cm 1 were observed when NaCN was added to a dimethyl-formamide solution of Ni[P(C6H5)3]3 (21). The rate dependence of... 

In their original suggestion, which was modified later, these workers visualised the formation of a "complex , or an activated monomer between NCA and the aprotic base, or its positive ion, if the initiator is an ion-pair. Such a complex conceptually resembles the one proposed by Wieland. For example, the initiation by lithium chloride in dimethyl-formamide solution was represented by the equation (44),... 

Fig. 4. UV grafting of acrylonitrile to cellulose film in dimethyl formamide solution with 10% water and 0.01 M 2,7 anthraquinone sodium disulfonate (112). — in air, C —in vacuo...

Figure 29.17 Simulation results showing the fraction of the total current at each of 25 segments of the working electrode at different times during the constant-current electrolysis of 2.5 mAf anthraquinone and in 0.1 M tetrabutylammonium iodide-dimethyl-formamide solution. Total current 100 / A electrode dimensions 0.5 cm x 3 cm flat cell dimensions 0.5 cm x 0.9 cm x 3 cm.

The conversion occurs also in an aqueous suspension of proteinoid microspheres containing dopa in the polymer instead of tyrosine. Presumably, dopaquinone is formed from tyrosine or dopa within the proteinoid during illumination with the aid of ferrous chloride 13). These experiments were performed after studies of the conversion of ADP to ATP catalyzed by the quinone, chloranil, and ferrous ion in dimethyl-formamide solution with white light. The yield of ATP under these condition is 20% 13,14). 

A remarkable example of photoelectrocatalysis was studied by Bockris and Wass (1989). They used 5% aqueous DMF solution with p-Si and p-CdTe as the photoelectrodes. Photoelectrocatalysis was observed by decorating the electrode surfaces with a number of different metal atoms. However, a 103 times acceleration of the rate of the photoreduction of CdTe was found in the presence of 18 crown 6 ether19 in dimethyl formamide solution (Fig. 15.20). The presence of both the NR ion and the appropriate crown ether was the key to the acceleration of the reaction rate. The suggested sequence is ... 

Schoffstall, A.M., Barto, R.J., and Ramo, D.L. 1982. Nucleoside and deoxynucleoside phosphorylation in formamide solutions. Origins Life Evol. Biosph. 12 143-151. 

The reaction yield is 10%. It may be increased up to 37% by heating in dimethyl-formamide solution (Finger and Kruze [7].)... 

Ge4Sio]" and [Fe4S4CLi] clusters was synthesized from a formamide solution containing the surfactant cetylpyridinium bromide. ... 

Purine has also been obtained by heating formamide alone (72CPB623) and detected in reactions involving hot formamide (77CPB1923). Interpretation of mechanisms of reactions carried out in formamide solution must clearly be made with care. However the distribution of and labels in purine derived from [ C, NJHCN and formamide has suggested the mechanism outlined (Scheme 55) (78TL4039). 

Only two structural studies have been reported for lithium solvates in non-aqueous solutions. In an XD study of concentrated formamide solution of LiCl [36] the lithium ion was found to be solvated by 5.4 formamide molecules in average and the Li-O distance was reported to be 2.24A, in keeping with the values found in diluted aqueous solutions. More recently, a detailed study has been performed by combination of the ND method with a series of theoretical methods on an 0.6 mol dm LiBr solution in acetonitrile [37]. The lithium ion was found to be tetrahedrally coordinated by three solvent molecules and one bromide ion. The Li-N distance resulted in 2.05 A. 

To formamide (20 mL) was added the crystalline sulfate of the appropriate pyrimidine-4,5-diamine (2.0 g). The sulfate salt was prepared in all cases by the addition of dil H2SO4 to an aqueous solution or suspension of the 4,5-diamine. The sulfate precipitated almost immediately in most instances however, in some cases, the salt crystallized slowly only after extended cooling of the aqueous solution. The formamide solution of the pyrimidine-4,5-diamine sulfate was refluxed for 20-25 min. A solution was rapidly obtained and precipitation of the purine occurred after 10 min. The solution was finally cooled, diluted with H O(10 mL) and allowed to remain overnight in the refrigerator, The crude product was removed by filtration from the neutral solution and washed with cold water. 

FIGURE 2-15 Refractive index of phenol-dimethyl formamide solutions (in GCl,) showing 1 1 compound formation. [From Arshid et al., J. Chem. Soc. 1955, 67-79.]... 

More direct evidence for mechanism (20a) may be adduced from the observation that hydantoin 3-acetic acid (XIV) can be isolated from the reaction between glycine NCA and lithium chloride in AT.AT-dimethyl-formamide solution (eqn. (22)) [37, 39]. 

The first separations of enantiomers in GC on cyclodextrin modified column were carried out by Sybilska et al. in 1983 [5], They applied a formamide solution of a-cyclodextrin as a stationary phase in the classical packed column. The column allowed an efficient separation of chiral monoterpenes - a- and P-pinenes into enantiomers. This system of using CDs in GC is characterised by obtaining high enantioselectivity factors, so enantioseparation is still possible for receiving not very efficient packed columns. Unfortunately, the columns appeared to be not very stable at higher temperatures. 

Fig. n.2. UV-Vis absorption spectra of (a) ZnS nanoc stallites of different sizes 3.5, 2.5 and 1.8 nm diameters in dimethyl formamide solution (inset shows the absorption spectrum of 1.8 nm ZnS nanoc stalline film) and (b)... 

Table VII. Properties of Sols and Gels from Acetone-Formamide Solutions of CA...

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