Formamide, solution preparation

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]. 

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. 

The pH of the formamide solutions used in hybridization is very important for the preservation of cellular morphology and optimal hybridization (Lomholt et al., 1989). Concentrated formamide has a pH of about 4.5 (note that pH measurement of undiluted formamide is incorrect), but after dilution with SSC (pH 7) and EDTA to 70% formamide, 2 X SSC and 1 mM EDTA it has a pH of 9.5. Chromosome preparations denatured with this solution have a poorly conserved morphology whereas titration of the solution to pH 7 with HCI produced both good morphology and increased specific hybridization. Moreover, if DeSO4 is used, autoclaving this accelerator reduces background. 

The preparation of 3-amino-1,2-benzisothiazole 249 can be done in different ways. A weU-known method started from 248, which was treated with a formamide solution containing NH3 [80] (Scheme 62). An alternative method started from hydroxylamine and N-(3H-benzo[c]l,2-dithiol-3-ylidene) acetamides (250) (obtained from 248 and thioacetic acid), and gave i r-(3-benzisothiazolyl)acetamide (251) (52-62%) hydrolyzed to amine 249 (48-88%) [81]. 

Mishra et al. [1994] and Bajpai et al. [1994] determined the microhardness of PMMA/PVDF and PMMA/PCTFE blends (Table 11.9) made by solution casting from dimethyl formamide solutions. The solutions containing the two polymers were heated at 110°C for 3 h and were poured into an optically plain glass mold to prepare pellets of the blends. The poured material was annealed at 75°C for 3 h. The samples were cut from the slowly cooled (24 h) pellets for this work. 

Dispersions can also be floccnlated by the addition of electrolytes, giving rise to systems containing large cations along with layers (or chains). Such systems cannot be prepared otherwise by direct intercalation. Intercalation compounds of TaS with complex aluminium oxycations and an iron sulphur cluster have been prepared in water-A -methyl-formamide solution [37]. 

Dimeihylamine, C2H7N, (CH3)2NH. Colourless, inflammable liquid with an ammoniacal odour, mp -96" C, b.p. 7°C. Occurs naturally in herring brine. Prepared in the laboratory by treating nitrosodimetbyl-aniline with a hot solution of sodium hydroxide. Dimethylamine is largely used in the manufacture of other chemicals. These include the solvents dimethylacetamide and dimethyl-formamide, the rocket propellant unsym-metrical dimethylhydrazine, surface-active agents, herbicides, fungicides and rubber accelerators. 

Aj Preparation of 3-Chloromethyl-6-Chloro-7-Sulfamyl-3,4-Dihydro-Benzothiadizine-1,1-Dioxide—Jo 8 ml of 40-50% chloroacetaldehyde aqueous solution and 7 ml of dimethyl-formamide are added 10 grams of 2,4-disulfamvl-5-chloroaniline. The mixture is heated on a steam bath for 2 hours after which it Is concentrated at reduced pressure. The residue Is triturated with water. The solid material is recrystallized from methanol-ether after-treatment with activated carbon to give 7.2 grams of product, MP 229°-230°C. 

B) Preparation of 2-(Hydroxyiminomethyl)-1-Methyl Pyridinium Chloride An aqueous solution of 15 ml of 1-methyl-2-picolinium chloride having a concentration of 477 mg/ml Is covered with 50 ml of benzene in an atmosphere of nitrogen and cooled to below 10°C. An aqueous solution of sodium hydroxide is added dropwise and the mixture is stirred for 5 minutes and allowed to stratify. The aqueous phase Is then drawn off and the benzene solution is added slowly to a solution of 3 ml of nitrosyl chloride in 175 ml of benzene containing 0.5 ml of dimethyl formamide at about 10°C in an atmosphere of nitrogen with good agitation. The mixture is then stirred for 1.5 hours and then extracted with four... 

Trimethylamine oxide is normally available as a hydrate, and for the present preparation it is necessary to convert it to its anhydrous form. A convenient way of doing this is as follows. A solution of 45.0 g. of trimethylamine oxide dihydrate (supplied by Beacon Chemicals) is dissolved in 300 ml. of warm dimethyl-formamide and placed in a three-necked flask set up for distillation. At atmospheric pressure the flask is heated and solvent distilled off until the boiling point reaches 152-153°. Then the pressure is reduced using a water aspirator, and the remainder of the solvent is distilled. At the end of the distillation the temperature of the bath is slowly raised to 120°. The residual anhydrous trimethylamine oxide (30 g.) can be dissolved in 100 ml. of chloroform and may remain in the same flask for use in the present preparation. 

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

A new family of hexagonal mesoporous all-germanium semiconductors was prepared by the surfactant-assisted cross-linking polymerization reaction of Zintl [Geg]" anions (Scheme 1) with Ge(lV) bridges in formamide/ethylenediamine solution (1) [43]. 

Clarke described a chromatographic system for the identification of corticosteroids including cortisone [2]. The method uses Whatman paper 1, impregnated with a 40% v/v solution of formamide in methanol, which must be prepared immediately before use. A saturated solution of formamide in chloroform was used as the solvent system [125]. The paper was equilibrated for 2 1/2 hours in a tank that had been saturated with the solvent for 24 hours. Development was continued in a descending manner until the solvent front had advanced about 35 cm. To locate the analytes,... 

Figure 27. Comparison of the L-Clu-induced integrated channel currents between two different preparations of GluR-incorporated BLMs upon injecting the identical concentration of l-GIu (0.10 nM). Applied potential +50 mV. Conditions 9.8 mM HEPES-NaOH (pH 7.6) containing 0.52 M NaCI, 0.19 mM CaCl2, 4.8 mM glycine, 24 pg mL of concanavalin A, 8.1 mM sucrose and 0.40 M formamide in both cis and trans side solutions. Proteoliposomes were injected only to the cis side and agonist solution was added to the trans side. Applied potential +50 mV. The l-GIu solution was injected to the trans side. ...

Typically they are prepared by the reaction of cyclo-Sg with a nucleophile in the presence of one of these cations. For example, the reaction of [PPNjSH with cyclo-Sg in ethanol yields the heptasulfide PFN][catena-Sj] 2EtOH. Orange-red crystals of the octasulfide [EGNH]2[catena-S ] are formed on treatment of a solution of cyclo-Sg in formamide with triethylamine and hydrogen sulfide [eqn (12.12)]. ... 

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