Dimethylformamide decomposition

To a solution of 18.9 grams (0.166 mol) n-heptaldehyde in 25 ml of isopropanol is added, with stirring, a solution of 19,1 grams (0.166 mol) of 1-aminohydantoin in 110 ml water acidified with concentrated HCI. The heavy white precipitate formed is filtered and washed, until acid free, with small amounts of water and ether. The yield of N-(n-hBptylidenB)-1-aminohydantoin is 14 grams of MP 150°C (with decomposition). This may be recrystal-lized from dimethylformamide. 

A solution of 3.55 parts of L-trypTtophanyl-L-methionyl-L-aspartyl-L-phenylalanine amide trifluoroacetate in 30 parts of dimethylformamide is cooled to 0 C, and 1.01 parts of tri-ethylamine are added. The mixture is stirred while 1.84 parts of N-tert-butyloxycarbonyl-(3-alanine 2,4,5-trichlorophenyl ester are added at 0 C. The reaction mixture is kept at 0°C for 48 hours and then at 20°-23°C for 24 hours. The mixture is added to a mixture of 100 parts of ice-water, 0.37 part of concentrated hydrochloric acid (SG 1.18), 1.2 parts of acetic acid and 20 parts of ethyl acetate. The mixture is stirred for 15 minutes at 0°-10°C and is then filtered. The solid residue is washed with water and then with ethyl acetate, and is dried at 40°-50°C under reduced pressure. There is thus obtained N-tert-butyloxycarbonyl-)3-alanyl-L-tryptophanyl-L-methionyl-L-aspartyl-L-phenylalanine amide, MP 213°C with decomposition. 

Cross-hnked polyacrylamides are a group of hydrophihc solid supports introduced primarily for preparation of biopolymers (Fig. 4). Unhke PS resins, polyacrylamides have excellent swelling capacity in both protic (water, alcohols) and aprotic (dichloromethane, dimethylformamide) solvents [88]. These beads are stable towards bases, acids, and weak reducing and oxidizing agents [89]. Predictably, conditions under which amide bonds are cleaved (i.e., sodium in liquid ammonia) [90] lead to rapid decomposition of the polymer. 

Table 3). The crystal inclusion compounds of the protic solvents are distinguished by relatively high points of thermal decomposition and, as before, the inclusion compound with dimethylformamide exhibits the highest tendency of formation. This is the result of competitive experiments. 

The palladium-catalyzed cross-coupling reaction featured in this procedure occurs under neutral conditions in the presence of many synthetically useful functional groups (e.g. alcohol, ester, nitro, acetal, ketone, and aldehyde). The reaction works best in N,N-dimethylformamide with bis(triphenylphosphine)palladium(ll) chloride, PdCI2(PPh3)2, as the catalyst. Lithium chloride is added to prevent decomposition of the catalyst.143 13 It is presumed that conversion of the intermediate aryl palladium triflate to an aryl palladium chloride is required for the transmetallation step to proceed.9... 

FIGURE 7.6 Decomposition of a mixed anhydride (A) to the 2-alkoxy-5(4//)-oxazolone and the alkyl carbonate.9 The latter is in equilibrium with the anion whose reaction (B) with a second molecule of anhydride produces pyrocarbonate and the acid anion whose reaction (C) with a third molecule produces the symmetrical anhydride. The oxazolone eventually reacts with the alcohol to give the ester. (D) Acyloxonium ions formed by reaction of the anhydride with dimethylformamide and tetrahydrofuran. 

Fluorinated poly(imide-ether-amide)s are readily soluble in organic solvents like dimethylformamide (DMF), N-methylpyrrolidone (NMP), pyridine or tetrahydrofu-ran (THF) and give flexible films by casting of such solutions. These polymers exhibit decomposition temperatures above 360°C, and glass transition temperatures in the 221-246° C range. The polymer films have a low dielectric constant and tough mechanical properties. 

Yields were improved by utilizing chemically modified charcoal [treatment with N,N-dimethylformamide dibutyl acetal (DMFBA) or N,0-bis(trimethylsilyl)acetamide (BSA)] due to suppression of H2O2 decomposition and ranged between 18 and 81%. Conversion and selectivity seem to depend extremely on the pre-treatment of charcoal with solutions of various pH values being highest for solutions with pH 7. 

The complexes are soluble in aromatic solvents and in THF. The tri-p-tolyl-phosphine complex has limited solubility in ether, and the tri-phenyl phosphine complex is insoluble in diethyl ether. Both complexes are insoluble in hexane and related solvents and decompose in chlorinated solvents. Limited solubility is achieved inA jV-dimethylformamide, but moderate decomposition occurs. 

This material is sufficiently pure for most purposes. If a purer product is desired, the crude material is dissolved in 300 ml. of dimethylformamide, 10 g. of activated alumina (48-100 mesh) is added, and the mixture is filtered. The filtrate is heated to 80-90° on a steam bath, then 1 1. of boiling water is added immediately (Note 2). The resultant mixture is cooled in an ice bath, and the light buff crystals of 2,5-diamino-3,4-dicyanothio-phene that separate are collected on a Buchner funnel and thoroughly washed with 500 ml. of acetone weight 26-28 g. (79-85%). The product has no definite melting point but sublimes with some decomposition when heated above 250°. 

Although toluene can be used for these reactions, boiling chloroform is preferred. The use of more polar solvents such as dimethylformamide (DMF) or acetonitrile fail to give any products, presumably because of the competitive decomposition of the bis-(dihydropyran). When the solubility of the starting material in boiling chloroform is poor, reaction yields can be improved by applying ultrasound. 

Umemoto [36] used external generation, followed by stopped-flow detection, to study the protonation of anthracene, anthraquinone, and benzophenone anions in dimethylformamide-water solutions using an apparatus similar to Figure 29.20c. The measured half-lives were about 1.5 min or more. In the case of anthracene, the decomposition rates agreed with those obtained from polaro-graphic measurements and the following scheme was proposed. 

When acetylene is recovered, absorption—desorption towers are used. In the first tower, acetylene is absorbed in acetone, dimethylformamide, or methylpyroUidinone (66,67). In the second tower, absorbed ethylene and ethane are rejected. In the third tower, acetylene is desorbed. Since acetylene decomposition can result at certain conditions of temperature, pressure, and composition, for safety reasons, the design of this unit is critical. The handling of pure acetylene streams requires specific design considerations such as the use of flame arrestors. 

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