Reaction paths of the water-assisted solvolysis of N,N-dimethylformamide

Density functional theory calculations were conducted on the title reactions with explicit inclusion of a variety of water molecules, H-CO-NMe2+MeOH+(H2O)n-->H-CO-OMe+HNMe2+(H2O)n. Geometries of transition states, reactant-like complexes and product-like ones were determined by the use of RB3LYP/6-31G(d) SCRF=dipole. Concerted paths were examined with n=0-3. Their Gibbs activation energies are larger than the experimental value. Stepwise paths were also investigated with n=2-4. The n=4 model has the energy close to the experimental value. However, when the catalytic water molecules were added to the n=4 one, the stepwise path was switched to the concerted one. A systematic comparison of the concerted path with n=2+1, 2+2, 2+3, 2+4, 2+5, 2+4+4, and 2+5+5 models was made, and the water-dimer based reaction path was found to be most favorable. The contrast between the concerted path of the amide solvolysis (and hydrolysis) and the stepwise one of the ester hydrolysis was discussed in terms of the frontier-orbital theory.     

Quenching of I(2P1/2) by NO2, N2O4, and N2O

Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.     

The electrochemical reaction of nitrate in N,N-dimethylformamide

Polarography, cyclic voltammetry and controlled-potential coulometry were used to study N,N-dimethylformamide solutions of nitrate. Nitrate is reversibly reduced in a one-electron step to NO(2). The diffusion coefficient of nitrate was polarographically estimated to be 4.6 x 10(-6) cm(2)/sec. Polarography in dimethylformamide was found to be a convenient method of analysis for nitrate in a solid fertilizer.     

The acidity scale of HCl solutions in N,N-dimethylformamide

The scale of the thermodynamic acidity of HCl solutions in DMF has been measured at 25 and 39.5 °C up to 15 mol L^–1 acid concentration by the indicator method. It is shown that in the HCl-DMF system the ionization of the nitroaniline-derived indicators occurs by the ion pair mechanism. Within the temperature range studied acidity is independent of temperature. Indicators of the nitroaniline series are used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1025–1028, June, 1994.     

Capillary electrophoresis in N,N-dimethylformamide

N,N-Dimethylformamide (DMF) is a dipolar protophilic solvent with physicochemical properties that makes it suitable as solvent for capillary electrophoresis (CE). It is prerequisite for the proper application of CE to adjust and to change the pH of the background electrolyte (BGE) in a defined manner. This was done in the present work using benzoic acid-benzoate by selecting different concentration ratios of acid and salt, and calculating the theoretical pH from the activity-corrected Henderson-Hasselbalch equation. The mobilities of the analytes (chloro- and nitro-substituted phenolates) were found to follow reasonably well the typical sigmoid mobility versus pH curve as predicted by theory. The actual mobilities and pK(a) values (at 25 degrees C) of the analytes were derived from these curves. pK(a) values were in the range of 11.1-11.7, being thus 3-4.4 units higher than in water. This pK(a) shift is caused by the destabilization of the analyte anion and the better stability (solubility) of the molecular analyte acid in DMF, which overcome the higher basicity of DMF compared to water. Absolute mobilities were calculated from the actual mobilities; they were between 32x10(-9) and 42x10(-9) m(2)/Vxs. Slight deviations of the measured mobilities from the theoretical mobility versus pH curve were discussed on the bases of ion pairing and heteroconjugation and homoconjugation of either buffer components or buffer components and analytes. Heteroconjugation was used as a mechanism for the electrically driven separation of neutral analyte molecules in a BGE where salicylate acted as complex forming ion. Rough estimation of the complexation constants for the phenolic analytes gave values in the range of 100-200 L/mol. Addition of water to the solvent decreased the effect of heteroconjugation, but it was still present up to the surprisingly high concentration of 20% water. Electrophoretically relevant parameters like ionic mobilities and pK(a) values, and conjugation and ion pairing are dependent on the water content of the solvent. The water uptake of DMF was measured when exposed to humidity of ambient air. The resulted behavior of the water uptake was found rather similar to that for acetonitrile and methanol.     

Polymerization of styrene in N,N-dimethylformamide

The polymerization of styrene in N,N-dimethylformamide (DMF) at 60°C has been studied both in the presence and absence of 4,4′-azobis-4-cyanopentanoic acid (ACV). Rates of polymerization were measured dilatometrically and gravimetrically, and degrees of polymerization were determined viscometrically. There was some discrepancy in the values of the transfer constant to DMF, C_s, obtained by analysis of the results. The most reliable value appeared to be 9.8 × 10^?6, from experimental data obtained in the absence of added ACV.     

The Reaction of Diethylthiophosphinyl Iodide,Et2P(S)I,with Nucleophiles

The compound Me₂AsSI can exist in two different forms, either as dimethylarsinosulfenyl iodide [or (iodothio)dimethylarsane)], Me₂As–S–I ( A ), or as dimethylthioarsinyl iodide (or dimethylarsinothioic iodide), Me₂As(S)–I ( B ). To confirm that the structure of the product of the reaction between Bunsen's cacodyl disulfide Me₂As(S)–S–AsMe₂ and iodine is A and not B , the known diethylthiophosphinyl iodide (or diethylphosphinothioic iodide), Et₂P(S)–I ( 2 ) was prepared and its hydrolytic stability and reactivity towards a variety of nitrogen, phosphorus(III), arsenic(III), oxygen, and sulfur(II) nucleophiles were studied. The results indicated that only a few reactions of 2 resembled those of A , thus strengthening the proposal that the reaction of Bunsen's cacodyl disulfide with iodine produced A and not B . A series of ³¹P NMR chemical shifts of diethylthiophosphinyl moiety is also reported. Et₂P(S)–DMAP, synthesized and isolated during the presented study, is the ethyl analogue of Me₂P(S)–DMAP, previously described as an important molecule. In our case, Et₂P(S)–DMAP was found to be a good intermediate for the synthesis of phosphoryl or thiophosphoryl derivatives since it was more reactive than 2 towards nucleophiles.     

The Henicosaphosphide Iodides of Potassium and Rubidium,K4P21I and Rb4P21I

The novel ternary polyphosphides M₄P₂₁I (M = K, Rb) have been synthesized from the elements in single crystalline form, representing further examples for the formation of mixed crystals between simple salts and binary phosphides. They form as ruby‐red platelets and dark‐red prisms, respectively, and are only slightly sensitive to moisture and oxygen. The compounds are isotypic (Ccmm (no 63); Z = 4; oP104; K₄P₂₁I: a = 12.853Å; b = 21.795Å; c = 9.748Å; 1168 hkl, R = 0.033; Rb₄P₂₁I: a = 13.281Å; b = 21.868Å; c = 9.771Å; 777 hkl, R = 0.053) and feature corrugated 2D networks formed from two different types of polymerized P₇ units. The networks form large cavities filled by M⁺ and I^‐ ions. Zigzag chains of condensed trigonal M₆ prisms, centered by the I^‐ anions, separate the polyphosphide nets. The mean homoatomic P‐P bond length (d = 2.216Å) corresponds to a P‐P single bond. However, the individual P‐P distances vary with position and function (2.126 ‐ 2.247Å) and these are compared with those of the isolated P₂₁^‐3 anion.     

Hochdrucksynthese von BaSr2P6N12 und BaCa2P6N12 und Strukturvergleich der Reihe BaP2N4, BaCa2P6N12 und BaSr2P6N12

High‐Pressure Synthesis of BaSr₂P₆N₁₂ and BaCa₂P₆N₁₂ and Comparison of the Structures of BaP₂N₄, BaCa₂P₆N₁₂, and BaSr₂P₆N₁₂ The novel nitridophosphates BaCa₂P₆N₁₂ and BaSr₂P₆ N₁₂ were obtained by means of high‐pressure high‐temperature synthesis utilizing the multianvil technique (1200 °C, 5 GPa). The complex anion [PN₂^?] of the title compound is formally isoelectronic with silica. The crystal structure was solved from powder data and refined by the Rietveld method (BaCa₂P₆N₁₂: , Z = 4, a = 9,9578(2) Å; BaSr₂P₆N₁₂: , Z = 4, 10,0705(2) Å). The crystal structures are derived from that of BaP₂N₄ which is isotypic with a high pressure phase of CaB₂O₄ and BaGa₂S₄. For each compound the ³¹P solid state NMR spectrum yielded a single resonance (BaCa₂P₆N₁₂: 7.4 ppm; BaSr₂P₆N₁₂:3.9 ppm).     

N,N-dimethylformamide: a multipurpose building block

Often used as a common solvent for chemical reations and utilized widely in industry as a reagent, N,N-dimethylformamide (DMF) has played an important role in organic synthesis for a long time. Numerous highly useful articles and reviews discussing its utilizations have been published. With a focus on the performance of DMF as a multipurpose precursor for various units in numerous reactions, this Minireview summarizes recent developments in the employment of DMF in the fields of formylation, aminocarbonylation, amination, amidation, and cyanation, as well as its reaction with arynes.     

Volumetric properties of ammonium nitrate in N,N-dimethylformamide

The densities of the ammonium nitrate in N,N-dimethylformamide (DMF) mixtures were measured at T = (308.15 to 348.15) K for different ammonium nitrate molalities in the range from (0 to 6.8404) mol·kg⁻¹. From the obtained density data, volumetric properties (apparent molar volumes and partial molar volumes) have been evaluated and discussed in the term of respective ionic and dipole interactions. From the apparent molar volume, determined at various temperatures, the apparent molar expansibility and the coefficients of thermal expansion were also calculated.     

Reactions of indoles with ortho esters,N,N-dimethylformamide and N,N-dimethylacetamide dialkyl acetals

Indole and N-methylindole react with oxa stabilized carbocations generated in situ from orthoformates to yield tris(3-indolyl)methane. The unsymmetrical isomers, e.g. 2-(N-methyl-3-indolyl)di(N-methyl-3-indolyl)-methane ( 4 ), were not formed as established by an independent synthesis. N,N-Dimethylacetamide dimethyl-acetal reacted with 2-alkyl substituted indoles to produce 1,1-bis(3-indolyl)ethanes ( 3 ).     

Crystallization-driven self-assembly of isotactic polystyrene in N,N-dimethylformamide

Herein we demonstrate crystallization-driven self-assembly of isotactic polystyrene(i PS) with high isotacticity and narrow molecular weight distribution and crystallization-induced switching of the morphology of i PS aggregates in N, N-dimethylformamide(DMF). The formation and morphology switching of the self-assembled aggregates of i PS are investigated by means of dynamic light scattering(DLS), scanning electron microscopy(SEM), differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WXRD). The results reveal that cooling DMF solution of i PS promotes i PS chains to self-assemble into spherical aggregates with a gelled core cross-linked by microcrystals, which is surrounded by solvent-swollen corona. Furthermore, crystallization induces the deformation of i PS aggregates from spherical to plate-like or nest-like.     

Thermodynamics of solution of proto- and mezoporphyrins in N,N-dimethylformamide

This paper describes the results of thermodynamic study of dissolution of proto- and mesoporphyrins in liquid N,N-dimethylformamide (DMF) at different temperatures. Enthalpies of solution and solubility of protoporphyrin dimethylester (PDE) and mesoporphyrin dimethylester (MDE) in DMF have been obtained from T = (298 to 318) K. Free energies, enthalpies, entropies and heat capacities of solution have been computed from the combination of enthalpic and solubility data via the Gibbs–Helmholtz equation. We have shown that for all blood porphyrins this approach reproduces both free energies of solution and solubility values for the physiological temperature range.     

Reaction of [P3N3Cl4(NH2)2] with [HN(POCl2)2]; The crystal structure of the phosphazenium salt [P3N3HCl4(NH2)2]+[N(POCl2)2]−

The reaction of diaminotetrachloro-cyclotriphosphazene with tetrachloride of μ-imino-diphosphoric acid leads to the formation of the salt-like compound [P₃N₃HCl₄(NH₂)₂]⁺[N(POCl₂)₂]⁻ which identity was unambiguously established by means of X-ray structure analysis. The structure is composed of [P₃N₃HCl₄(NH₂)₂]⁺ cations and [N(POCl₂)₂]⁻ anions joined by a system of H-bonds. As in other phosphazenium salts, the protonation of the ring N atom leads to significant changes in the endocyclic P N bond lengths.