Sodium In Liquid Ammonia Research Articles

The Hydronaphthalide Monoanion: Isolation of the "red transient" Birch Intermediate from liquid Ammonia.

Birch reactions employing alkali metals in ammonia have been a well-established method for the reduction and functionalisation of aromatic compounds for nearly 100 years. Speculations regarding intermediates in the reaction pathway have been discussed since the beginning. We hereby report the isolation of NMe4(HNaph) (1), a kinetically trapped intermediate of the Birch reaction of naphthalene and sodium in liquid ammonia. 1 has been fully characterised and has been shown to continue to react to 1,2/1,4-dihydronaphthalene - the Birch product of the reduction of naphthalene. The reactivity of 1 was investigated towards activity as an electron and hydride transfer agent with both, elements and small organic molecules. 1 demonstrates a tamed reduction potential which allows for controlled reactions such as the selective formation of hexasulphide and hexaselenide anions.

Synthesis of ultra-high-temperature nitride amorphous bulk by reaction of halide precursors with sodium in liquid ammonia

Amorphous Si-B-N nanoparticles of uniform composition tunable over the entire range spanning pure Si3N4 to pure BN was synthesized through a simple homogeneous chemical reaction of the mixture of SiCl4 and BBr3 with Na in liquid ammonia. With these amorphous nanopowders, dense amorphous bulk material was obtained with SPS sintering at the temperature before the crystallization. The dense amorphous bulk of Si3B3N7 exhibited the highest value of hardness (8.8 GPa), flexural strength s (545 MPa), and fracture toughness KIC (10.6 MPa m1/2). These are significantly higher than those reported for other crystalline ceramics of the same composition and surpass those of the completely dense crystalline ceramics. The fully-dense amorphous bulk material exhibited excellent resistance to oxidation up to 1550 °C.

Synthesis, characterization and cure behavior of phenol-crotonaldehyde-resorcinol resins

Phenol-crotonaldehyde-resorcinol (PCR) resins were synthesized by base-catalyzed condensation reaction of phenol, crotonaldehyde, and resorcinol. Three different bases utilized for condensation reaction were sodium hydroxide, hexamethylenetetramine (hexa) and liquid ammonia. The NaOH catalyzed resins were found to be thermoplastic in nature, while hexa- and liq. NH3 catalyzed resins showed thermoset behavior. Effect of varying mole ratio of phenol, crotonaldehyde and resorcinol was studied to investigate the curing and thermoset behavior of the synthesized resins. The average molecular weight of the resins was determined by gel permeation chromatography (GPC). All synthesized resins were characterized by various analytical techniques such as FT-IR, NMR, TGA, DSC and FE-SEM/EDX.

Synthesis of the Tetragonal Phase of Zintl's NaTl and Its Structure Determination from Powder Diffraction Data.

A tetragonal distortion of the long-time known NaTl structure at 298 K was observed in different experimental setups, including Zintl’s original procedure of reducing Tl(I)-iodide by sodium liquid ammonia solutions. The powder diffraction pattern obtained by the high temperature synthesis using classical solid-state techniques allowed a model-independent unambiguous structure solution and refinement of tetragonal distorted NaTl (Rp = 0.0179, wRp = 0.0246, R = 0.0477, wR = 0.0527, GooF = 1.24).

L‐Menthol‐Assisted Synthesis of P‐Stereogenic Phosphinous Acid Amides and Phosphine‐Boranes

Diastereomerically pure phenylphosphonous acid‐borane l‐menthyl ester N,N‐diethylamide was obtained through the fractional crystallization of a diastereomeric mixture of compounds synthesized from PhPCl2, l‐menthol, diethylamine, and BH3·THF. Treatment of racemic or diastereomerically pure phenylphosphonous acid‐borane derivatives with sodium in liquid ammonia followed by the addition of an electrophile led to the formation of phosphinous acid‐amides. Surprisingly, these compounds undergo preferential P–N bond cleavage under Birch reduction conditions.

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Synthesis, characterization and sintering of Si-C-N nano-powders via sodium reduction in liquid ammonia

Si-C-N nano-powders with tunable carbon content were synthesized through the reduction of silicon tetrachloride (SiCl4) and trichloromethylsilane (SiCl3CH3) solution by sodium in liquid ammonia. The nano-powders contain two domains of structure, Si-C-N amorphous or continuous random networks (CRNs), and free carbon. The carbon content in Si3+nCnN4 CRNs, is tunable from n=0 to n=1. Free carbon will appeared with the increase of the C/Si mole ratio when C/Si is higher than 1/4. The crystallization of amorphous Si-C-N powders occurs at temperatures ranging from 1300°C to 1500°C depending on the carbon content. The additive-free dense Si-C-N ceramics with relatively low porosity were fabricated by Spark Plasma Sintering (SPS).

Nanoscale Iron Nitride, ε-Fe3N: Preparation from Liquid Ammonia and Magnetic Properties

e-Fe3N shows interesting magnetism but is difficult to obtain as a pure and single-phase sample. We report a new preparation method using the reduction of iron(II) bromide with elemental sodium in liquid ammonia at −78 °C, followed by annealing at 573 K. Nanostructured and monophasic oxygen-free iron nitride, e-Fe3N, is produced according to X-ray diffraction and transmission electron microscopy experiments. The magnetic properties between 2 and 625 K were characterized using a vibrating sample magnetometer, revealing soft ferromagnetic behavior with a low-temperature average moment of 1.5 μB/Fe and a Curie temperature of 500 K. TC is lower than that of bulk e-Fe3N (575 K) [Chem. Phys. Lett 2010, 493, 299], which corresponds well with the small particle size within the agglomerates (15.4 (±4.1) nm according to TEM, 15.8(1) according to XRD). Samples were analyzed before and after partial oxidation (Fe3N–FexOy core–shell nanoparticles with a 2–3 nm thick shell) by X-ray diffraction, transmission electron m...

Fabrication of dense Si<sub>3</sub>N<sub>4</sub> ceramics via coating amorphous Si<sub>3</sub>N<sub>4</sub> nano-powders by sodium reduction in liquid ammonia

Commercial Si3N4 powders coated with 0-30% amorphous Si3N4 nano-powders were fabricated successfully. Amorphous Si3N4 nano-powders coating were prepared through the reduction of silicon tetrachloride (SiCl4) by sodium in liquid ammonia at -45 degrees C. Dense Si3N4 ceramics with 97.2% relative density of theoretic value were obtained from Si3N4 micro-powders coated with 30% nano-powders sintered by spark plasma sintering at 1500 degrees C without sintering additives. (C) 2017 The Ceramic Society of Japan. All rights reserved.

Synthesis and sintering of silicon nitride nano-powders via sodium reduction in liquid ammonia

Nano-sized silicon nitride powders were synthesized through the reduction of silicon tetrachloride (SiCl4) by sodium in liquid ammonia at around −40°C.The product was in uniform particles of several nanometers, and in the amorphous form. The amorphous structure was stable up to 1200°C and turned to the crystal structure of α-Si3N4 at 1300°C, and then to β-Si3N4 structure when heated at temperatures higher than 1450°C.Via spark plasma sintering (SPS) dense bulks with 97.9% relative density of theoretic value and the grain size of 100–300nm was successfully fabricated at 1500°C without any sintering additives.

Investigation of the supramolecular structure of PTFE via two-stage chemical etching

The supramolecular structure of polytetrafluoroethylene (PTFE) is studied by high-resolution electron microscopy using two-stage chemical etching of the surface, consisting in the chemical reduction of macromolecules in a solution of sodium naphthalene or sodium in liquid ammonia, followed by treatment of the surface with fuming nitric acid. The existence of regular grooves on the end faces of lamellae in the initial PTFE is proven, which leads to the conclusion that the lamellae possess a fibrillar structure. The significant size excess of the crystalline domain over the diameter of the fibrils is explained by coherent stacking of the crystalline regions of fibrils in the lamellae. The existence of fine-grained structure in the initial PTFE is found on the scale of approximately 100 μm. It is confirmed that the radiation modification of PTFE in the melt leads to the formation of centrally symmetric structures, namely, spherulites with radial orientation of the fibrils and macromolecules.

Modified Birch Reduction for the Introductory Undergraduate Organic Laboratory

The Birch reduction is a reaction commonly taught in the second-year undergraduate organic curriculum that involves the reduction of an aromatic compound to an alicyclic product using sodium metal and liquid ammonia. The experimental procedure can be challenging for novice chemists and thus has not been widely performed in introductory organic laboratories. An experimental procedure appropriate for introductory organic students is described that utilizes commercially available sodium-impregnated silica gel that is safer and easier to handle. This modified Birch reduction effectively reduces naphthalene to 1,4-dihydronaphthalene while minimizing safety concerns associated with the use of alkali metals and liquid ammonia.

Synthesis of Fine Iron–Cobalt Alloy Particles by the Co-Reduction of Precursors with Solvated Electrons in Sodium–Ammonia Solution

Fine iron­cobalt alloy particles were synthesized by the co-reduction of their precursors with sodium in liquid ammonia. The reaction took place instantaneously because of the highly reductive solvated electrons. Very reactive, fine particles of the order of 310 nm size were obtained. Annealing process is crucial for the magnetic properties of the products, the saturation magnetization being ranging from 29 to 238A·m2·kg11. One spot reduction with solvated electrons and the consequent annealing treatment in the synthesis vessel has potential ability for the synthesis of a variety of metal and alloy particles. [doi:10.2320/matertrans.M2013375]

Boron complexes of redox-active diimine ligand

Boron complexes (dpp-bian)BCl2 (1) and (dpp-bian)BX (X = Cl, 2; Br, 3) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) have been prepared by reacting mixtures dpp-bian-BX3 (1 : 1) with one (1) and two (2 and 3) equivalents of sodium correspondingly in toluene. Complexes 2 and 3 reveal a moderate stability against ambient oxygen and moisture. The reaction of complex 2 with PhC≡CLi gave compound (dpp-bian)B-C≡CPh (4). Treatment of 2 with potassium hydroxide afforded complexes (dpp-bian)B-OH (5) and (dpp-bian)B-OK (6). Boron amide (dpp-bian)B-NH2 (7) has been isolated from the reaction of compound 1 with sodium in liquid ammonia. Borane (dpp-bian)B-H (8) can be prepared by the reactions of complexes 2 and 3 with LiAlH4. Diamagnetic compounds 2-8 have been characterized by IR, (1)H and (11)B NMR spectroscopy; paramagnetic complex 1 has been studied by the ESR method. Molecular structures of 2, 5, 7 and 8 have been determined by X-ray crystallography.

Synthesis of the Pleuromutilin Antibiotic SB-268091: A New Practical and Efficient Synthesis of Quinuclidine-4-thiol

A synthesis of the pleuromutilin antibiotic SB-268091 is described which includes a new and improved route to the quinuclidine-4-thiol ligand. This chemistry has been run on multikilo scale and involved a reductive double debenzylation using sodium in liquid ammonia. Alternative conditions have been developed to prepare quinuclidine-4-thiol which avoid the use of sodium in liquid ammonia. The generality of this process to prepare differentially S-protected quinuclidine-4-thiols is also discussed and exemplified by the preparation of a range of analogues.

Unique thermodynamic relationships for Δf H o and Δf G o for crystalline inorganic salts. I. Predicting the possible existence and synthesis of Na2SO2 and Na2SeO2

The concept that equates oxidation and pressure has been successfully utilized in explaining the structural changes observed in the M(2)S subnets of M(2)SO(x) (x = 3, 4) compounds (M = Na, K) when compared with the structures (room- and high-pressure phases) of their parent M(2)S `alloy' [Martínez-Cruz et al. (1994), J. Solid State Chem. 110, 397-398; Vegas (2000), Crystallogr. Rev. 7, 189-286; Vegas et al. (2002), Solid State Sci. 4, 1077-1081]. These structural changes suggest that if M(2)SO(2) would exist, its cation array might well have an anti-CaF(2) structure. On the other hand, in an analysis of the existing thermodynamic data for M(2)S, M(2)SO(3) and M(2)SO(4) we have identified, and report, a series of unique linear relationships between the known Δ(f)H(o) and Δ(f)G(o) values of the alkali metal (M) sulfide (x = 0) and their oxyanion salts M(2)SO(x) (x = 3 and 4), and the similarly between M(2)S(2) disulfide (x = 0) and disulfur oxyanion salts M(2)S(2)O(x) (x = 3, 4, 5, 6 and 7) and the number of O atoms in their anions x. These linear relationships appear to be unique to sulfur compounds and their inherent simplicity permits us to interpolate thermochemical data (Δ(f)H(o)) for as yet unprepared compounds, M(2)SO (x = 1) and M(2)SO(2) (x = 2). The excellent linearity indicates the reliability of the interpolated data. Making use of the volume-based thermodynamics, VBT [Jenkins et al. (1999), Inorg. Chem. 38, 3609-3620], the values of the absolute entropies were estimated and from them, the standard Δ(f)S(o) values, and then the Δ(f)G(o) values of the salts. A tentative proposal is made for the synthesis of Na(2)SO(2) which involves bubbling SO(2) through a solution of sodium in liquid ammonia. For this attractive thermodynamic route, we estimate ΔG(o) to be approximately -500 kJ mol(-1). However, examination of the stability of Na(2)SO(2) raises doubts and Na(2)SeO(2) emerges as a more attractive target material. Its synthesis is likely to be easier and it is stable to disproportionation into Na(2)S and Na(2)SeO(4). Like Na(2)SO(2), this compound is predicted to have an anti-CaF(2) Na(2)Se subnet.

Synthesis of a new 2‐amino‐glycan, poly‐(1→6)‐α‐D‐mannosamine, by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives

AbstractA stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative (3) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative (6), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (Mn) of 2.3 × 104 to 2.9 × 104 with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A Novel Method for the Preparation of Nano-Sized Nickle Powders

Nano-sized nickel powders were prepared through a wet chemical reduction, of NiCl2 by sodium in liquid ammonia at -45 °C, and a subsequent heat-treatment in vacuum at 300 °C. The prepared product was systematically characterized by X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM), and BET specific surface area measurement. The results show that the product was composed of nano-sized nickel particles, with average particle diameter of about 20 nm, and specific surface area of about 30 m2g-1. The possible formation mechanism of the nano-sized nickel powder was also discussed briefly.

Water-Soluble Nanodiamond

Reduction of the graphenic edges of annealed nanodiamond by sodium in liquid ammonia leads to a nanodiamond salt that reacts with either alkyl or aryl halides by electron transfer to yield radical anions that dissociate spontaneously into free radicals and halide. The free radicals were observed to add readily to the aromatic rings of the annealed nanodiamond. Nanodiamonds functionalized by phenyl radicals were sulfonated in oleum, and the resulting sulfonic acid was converted to the sodium salt by treatment with sodium hydroxide. The solubility of the salt in water was determined to be 248 mg/L. Nanodiamond functionalized by carboxylic acid groups could be prepared by reacting 5-bromovaleric acid with the annealed nanodiamond salt. The solubility of the sodium carboxylate in water was found to be 160 mg/L.

ChemInform Abstract: Sodium in Liquid Ammonia — A Versatile Tool in Modifications of Arylphosphine Oxides.

AbstractThe reaction of tertiary arylphosphine oxides with sodium in liquid ammonia is strongly influenced by the substrate structure.