Study of the initial stages of alkoxo synthesis involving Ti(OBu)4 and cyclophosphites

The reactivities of cyclophosphite precursors in alkoxo syntheses involving titanium(iv) tetra(n-butoxide) were studied by ³¹P NMR and IR spectroscopy. 2-Diethylamido-4-methyl-1,3,2-dioxaphosphinane and 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane in benzene are inert toward Ti(OBu)₄. Gelation is accompanied by hydrolysis 2-diethylamido-4-methyl-1,3,2-dioxaphosphinane to give the corresponding hydrophosphoryl compound, while 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane remains intact during gelation.     

Gelation of organic solvents by N-(n-tetradecylcarbamoyl)-l-amino acids

A series of N-(n-alkylcarbamoyl)-l-amino acid amphiphiles with different amino acid head groups were designed and synthesised. The gelation abilities of these amphiphilic molecules were studied in toluene and p-xylene solvents. The hypothesis that steric crowding at the chiral head group destroys gelation ability of the amphiphile was examined. Indeed, beside l-alanine-based amphiphile, only l-serine and l-aspartic acid derivatives were found to gelate the organic liquids efficiently in the presence of a small quantity of water. The gels were characterised by a number of methods, including FT-IR, NMR and X-ray diffraction spectroscopy, scanning electron microscopy (SEM) and rheology. The SEM micrographs revealed three-dimensional networks of ribbon-like aggregates. The organogels were observed to be thermo-reversible in nature and have sufficient mechanical strength. The gels have gel-to-sol transition temperatures above the physiological temperature (310 K).     

Organogels from water-in-oil microemulsions

A new family of organogels is described. They originate from water-in-oil microemulsions, from which the name microemulsion gels or microemulsion-based gels is derived. Two different types of such gels are presented here, referred to asgelatine gels andlecithin gels, respectively. In the case of gelatine gels, the initial ternary system typically consists of isooctane, AOT (bis 2-ethylhexyl sodiumsuccinate) and water; gelation is induced by solubilization of gelatine in the water microphase above a critical concentration. In the case of lecithin gels no polymeric material is needed. Starting from a reverse micellar solution of lecithin (50–200 mM) in an organic solvent, gelation is induced by the addition of a small amount of water. The molar ratio of water to lecithin typically varies between 1 and 12 for the 50 different solvents investigated to date. These gels are isotropic, thermoreversible and optically transparent.For both microemulsion gels the influence of the concentration of the components on gelation is presented in the form of preliminary phase diagrams.The physico-chemical properties of these organogels were characterized using a variety of techniques such as NMR, DSC, dynamic shear viscosity measurements, and light scattering. Based on these measurements, preliminary models for the structure of these novel systems were developed.It is possible to co-solubilize a variety of reactive molecules in these gels. Therefore, it may be possible to use these organogels for a number of chemical, pharmaceutical, and cosmetic applications.Paper presented at the Workshop on Ringing Gels and Cubic Phases, Bayreuth, October 25–26, 1988.     

A hydrogel formed by cetylpyrrolidinium bromide and sodium salicylate

A novel hydrogel constructed by N-methyl-N-cetylpyrrolidinium bromide (C₁₆MPBr) and sodium salicylate (NaSal) is investigated using ¹H NMR, FT-IR, SEM, and rheological measurements. Through the rheological characterization of the hydrogels, both the NaSal concentration and pH have significant effects on the formation and properties of the gels. ¹H NMR, FT-IR, and SEM have also been employed to investigate the molecular arrangement and morphology of the gels. Hydrophobic and electrostatic interactions are considered as the main driving forces to form the gels.     

Formation of functional phosphosilicate gels from phytic acid and tetraethyl orthosilicate

Phosphosilicate gels with high phosphorus content (P mol% > Si mol%) have been prepared using phytic acid as the phosphorus precursor, with tetraethyl orthosilicate (TEOS). It is shown that the structure of phytic acid is maintained in both the sols and those gels dried at a low temperature (i.e. ≤120 °C). Solid state ²⁹Si and ³¹P NMR suggest that the gel network is primarily based on tetrahedral silicon and that phosphorus is not chemically incorporated into the silicate network at this point. X-ray diffraction shows the gel to be amorphous at low temperatures. After heat treatment at higher temperatures (i.e. up to 450 °C), P–O–Si linkages are formed and the silicon coordination changes from tetrahedral to octahedral. At the same time, the gel crystallizes. Even after this partial calcination, ³¹P NMR shows that a large fraction of phytic acid remains in the network. The function of phytic acid as chelating agent is also maintained in the gels dried at 120 °C such that its ability to absorb Ca²⁺ from aqueous solution is preserved.     

The Reaction Activity of Aromatic Carbonyl Compounds with Diphenylphosphine Oxide Studied by 31P NMR

Abstract

A series of α-hydroxyphosphine oxides were prepared by the reactions of diphenylphosphine oxide and aromatic carbonyl compounds and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, ESI-MS, and HR-MS spectra. The reaction rates and experimental conditions of aromatic aldehydes and aromatic ketones were obviously different due to the activity of their carbonyls. The different substituents of the aromatic aldehydes affected the reaction rate too, and the quantitative reactivity of their substituent conformed to the Hammett equation. The results were confirmed by ³¹P NMR spectroscopy.     

Hybrid RSiO1.5/B2O3 Gels from Modified Silicon Alkoxides and Boric Acid

A new sol-gel route, without any external water addition, for the preparation of hybrid RSiO_1.5/B₂O₃ gels (R = Me, Et, Vi) is reported. The gels are easily synthesized by reacting B(OH)₃ with the liquid silicon alkoxide. The gels have been characterized mainly by FT-IR and ¹¹B MAS NMR spectroscopy. The results show that this new sol-gel process allows the formation of a homogeneous borosilicate gel in which trigonal BO₃ units are incorporated into the siloxane network via B—O—Si bonds.     

Substituent Effects on 31P NMR Chemical Shifts and 1JP–Se of triarylselenophosphates

The effect of electron-withdrawing (EW) and electron-releasing (ER) substituents on the ³¹P NMR chemical shifts and the structural parameters of a series of tris-(p-X-aryl)selenophosphates is reported in this article. Similarly to O-aryl phosphates and O-aryl thiophosphates, EW groups attached to aromatic rings induce a shielding effect on the ³¹P NMR signal. After a detailed experimental and theoretical analysis, we confirmed that the selenium atom is the main part responsible for the charge density transfer toward phosphorus through a back-bonding effect. The obtained ¹J_P-Se values for the complete series agree with this observation.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

A small-angle neutron scattering study of the ethyl (n-octyl) phosphate micelles in water

Summary Mixed-double chain anionic surfactants, barium- and lithium-salts of ethyl(n-octyl) phosphate (EOP), which are asymmetric in the molecular shape, and a series of identical chain di-n-alkyl phosphate lithium salts have been synthezized. The limiting partial molar volume of a PO ₄ ^– group (23.43±0.41 cm³ mol^–1) for use in small-angle neutron scattering analysis was determined by density measurements of a series of identical chain di-n-alkyl phosphate lithium salts. For lithium EOP-D₂O system, a critical micellar concentration (2.3 wt%) was determined by³¹P NMR spectra. The micellar shape and size in the EOP-water binary system has been investigated by using small-angle neutron scattering (SANS) spectra. It has been found that the micelles of barium EOP in water have the shape of a prolate spheroid and aggregation numbers (n) equal to 48 at 23°C and 52 at 50°C. For the lithium EOP-micellar system, it has been found that the minimum micelle with an aggregation numbern=21 is spherical and micellar growth and variation from the spherical to the prolate shape might occur with an increase in concen tration above the CMC.     

NMR studies on solid cyclohexaamylose inclusion compounds

Orthorhombic inclusion compounds of cyclohexaamylose with methanol,n-propanol, acetic acid and water as guest molecules were studied using¹³C and²H NMR techniques.¹³C chemical shifts were correlated with structural data, whereas²H NMR lineshapes were used to derive information on guest molecule motions.Issued as NRCC No. 25568. Presented in part at the 2nd International Symposium on Clathrate Compounds and Molecular Inclusion Phenomena, Parma, Italy, 30 Aug.–3 Sept. 1982     

Gelation of tenuous titania gels in a reverse micellar medium

Tenuous gels of TiO₂ are synthesized from titanium isopropoxide in a reverse micellar medium. The volume fraction of TiO₂ in these gels is equal to 0.2%. The chemical and aggregative mechanisms are studied using ¹H NMR, small-angle X-ray scattering, dynamic and static light scattering. The alkoxide hydrolysis occurs at the first stage of the gelation. Small clusters (70–80 Å) are produced. The aggregation induces mass fractal structures with fractal dimensions depending on the solvent used in the synthesis: 1.4<D _f<1.9. The interpretation of these results is based on interactions between the growing inorganic chains and the surfactant molecules.     

Phosphate additives determination in meat products by 31-phosphorus nuclear magnetic resonance using new internal reference standard: hexamethylphosphoroamide

New ³¹P NMR internal reference standard - hexamethylphosphoroamide (HMPA) was applied for determination of added polyphosphates and their ionic forms in raw pork meat and meat products. Phosphate species were determined after extraction with a boric acid buffer (pH = 9) and EDTA solution, using internal standard (HMPA) procedure. Hexamethylphosophoroamide was also used as the NMR reference standard. Linear correlations between phosphates and polyphosphate concentrations and ³¹P NMR signal areas were found in the range 81-5236 mg P/dm³, presenting 95-99% recovery and variation coefficient (CV) ≤ 5%. Studied HMPA procedure revealed shorter analysis time and the same recovery (>95%) and precision (CV = 1.3-2.7%) in comparison to MDPA method. Results of phosphate determination by both ³¹P NMR methods were tested against the molybdenumvanadate yellow spectrophotometric method (standard PN-ISO 13730, 1999) using standard reference material (certified phosphate solution).     

Preparation of trisodium O-monoalkyl and O-monoaryl diphosphates

Trisodium O-methyl, O-butyl, O-phenyl, and O-(4-nitrophenyl) diphosphates were synthesized from sodium dimethylamido-O-(2-cyanoethyl) phosphate and O-alkyl-and O-aryl phosphoric acids. While in the previously described method, sodium hydroxide was used for the preparation of O-phenyl diphosphate, in our current work, we present an improved protocol, where sodium methoxide is used to increase the yields of O-alkyl and O-aryl diphosphates. The structures of final compounds were determined by ¹H NMR, ³¹P NMR, and IR spectroscopy. The sodium O-alkyl- and O-aryl diphosphate salts prepared by this method may be used for the study of biological activity of diphosphate analogues.     

Experimental and theoretical NMR studies of interaction between phenylalanine derivative and egg yolk lecithin

The interaction of phenylalanine diamide (Ac‐Phe‐NHMe) with egg yolk lecithin (EYL) in chloroform was studied by ¹H and ¹³C NMR. Six complexes EYL–Ac‐Phe‐NHMe, stabilized by N–H···O or/and C–H···O hydrogen bonds, were optimized at M06‐2X/6‐31G(d,p) level. The assignment of EYL and Ac‐Phe‐NHMe NMR signals was supported using GIAO (gauge including atomic orbital) NMR calculations at VSXC and B3LYP level of theory combined with STO‐3G_mag basis set. Results of our study indicate that the interaction of peptides with lecithin occurs mainly in the polar ‘head’ of the lecithin. Additionally, the most probable lecithin site of H‐bond interaction with Ac‐Phe‐NHMe is the negatively charged oxygen in phosphate group that acts as proton acceptor. Copyright © 2014 John Wiley & Sons, Ltd.     

Palladium(II) Complexes of 1-Phosphaisoprene Molecules and Polymers: Reversible Cross-Linking of a Phosphorus-Containing Polymer

The anionic polymerization of 1-phosphaisoprene [Mes*P=C(Me)−CH=CH₂ (E- 1 )] affords poly(1-phosphaisoprene) 2 in high yield (75 %). Concentrated solutions of polymer 2 (M_n=21,800 g mol⁻¹; Đ=1.02) a P-analogue of natural rubber, undergo gelation upon treatment with [Pd(cod)Cl₂] (0.15 P equiv). Evidence for P-coordination of 2 to Pd^II was obtained by ³¹P and ¹H NMR spectroscopy. The gelation is reversed by the addition of PMe₃ and the reformation of recoverable 2 along with [Pd^II−PMe₃] complexes were confirmed by ³¹P NMR spectroscopy. The use of labile metal-ligand bonds to reversibly form gels is unprecedented and has relevance to self-healing materials. In contrast, coordination of 2 to [Pd(η³-C₃H₅)(μ-Cl)]₂ affords the well-defined complex 2 ⋅ [Pd(η³-C₃H₅)Cl] which was characterized by ³¹P, ¹H, ¹³C{¹H} NMR spectroscopy and GPC. This polymer chemistry was complemented by detailed molecular model studies of the coordination chemistry of monomer 1-phosphaisoprene E- 1 with [Pd(cod)Cl₂] and [Pd(η³-C₃H₅)(μ-Cl)]₂].     

The preparation and analysis of fluoro-polyphosphates by F, P, 2D F-P HETCOR and 2D P-P COSY NMR

A complex mixture of fluoro-polyphosphates (FPPs) and polyphosphates was prepared by heating a mixture of NaF and sodium tripolyphosphate (STPP) at 600 °C in nitrogen atmosphere. Two-dimensional ³¹P-¹⁹F heteronuclear correlation spectroscopy (HETCOR) NMR was developed in identifying the atomic connection between F and P in the mixed FPPs. ¹⁹F, ³¹P and ³¹P-³¹P correlation spectroscopy (COSY) NMR methods were employed to identify the components of the mixture and measure the chain length of each FPP ingredient. NMR results clearly demonstrated that the mixture contains four kinds of fluoro-phosphates with different chain length of polyphosphate, which are monofluoro-phosphate (MFP), monofluoro-dipolyphosphate (MFDPP), monofluoro-tripolyphosphate (MFTPP) and difluoro-tripolyphosphate (DFTPP). Other phosphates and polyphosphates also were found in the mixture.     

Solubilization of Styrene and Acrylamide Monomers in Microemulsions

Abstract

Phase diagrams of sodium dodecyl sulfonate (DS)/n‐butanol/styrene/water systems with variable amounts of styrene were constructed at 40°C, and the effects of styrene on microemulsion stability were studied. The solubilization of styrene in these O/W microemulsion systems was investigated by ¹H NMR methods. The results show that the solubilization site shifts from the palisade layer to the inner core of microemulsion droplets when the molar fraction of styrene reaches 0.312. The solubilization of acrylamide in cetyltrimethylmethyl ammonium bromide (CTAB)/n‐butanol/10% n‐octane/water reverse microemulsions (W/O) was studied with a ¹³C NMR method. It was found that the acrylamide was mainly solubilized in the Stern layer of droplets at low acrylamide levels. However, when the mole fraction of acrylamide approaches 0.428, the acrylamide penetrates into the palisade layer and is distributed along the hydrocarbon chain of the surfactant.     

Spectra and structure of binary azeotropes. III. Acetone-n-hexane

Acetone and n-hexane form an azeotrope with the mole ratio 2:1. As a result of this phenomenon, some characteristic vibrational modes in FT-IR and some chemical shifts in ¹H NMR spectra changes. The amount of these changes is an indication of the extension of interaction between two components and their orientation in unit structure of the cluster. FT-IR and ¹H NMR spectra of pure substances and their azeotrope were recorded and spectral changes analyzed. Based on mole ratio of constituents, boiling point depressions, spectral changes in fundamental frequencies, and chemical shifts, unit structure of the azeotrope were deduced.     

Micellar effect of ionic surfactants in the reaction ofo-dimethylaminomethylphenol withp-nitrophenyl diphenyl phosphate

The effect of cetylpyridinium bromide (CPB) and sodium dodecyl sulphate (SDS) on the direction and the rate of the reaction ofo-dimethylaminomethylphenol (MP) withp-nitrophenyl diphenyl phosphate (1) has been studied by³¹P NMR and spectrophotometry. It was shown that the reaction of MP with1 proceeds in two steps both with and without the surfactant. The product of transesterification is formed in the first step. The second step is hydrolysis catalyzed by the aminomethyl group yielding equal amounts of diphenyl phosphate ando-dimethylaminomethyl phenyl phosphate. The reaction of MP with1 is catalyzed by CPB and inhibited by SDS. The ratio between the rates of the first and the second stages changes in the presence of surfactant. The parameters of the reaction of MP with1 inhibited by micellar SDS were calculated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 242–245, February, 1994.     

31P NMR NON-EQUIVALENCE OF THE DIASTEREOISOMERIC PHOSPHONODIDEPSIPEPTIDES. PART II1

Abstract

³¹P chemical shifts are reported for 24 different models of diastereoisomeric phosphonodidepsipeptides coupled from the N-protected L-aminoacids and dibenzyl esters of chiral 1-hydroxyalkylphosphonic acids. The ³¹P NMR nonequivalence variations with the changing of didepsipeptide structure, solvent and temperature were investigated. Amide cis-trans isomerism were observed in the case of Z-L-proline derived didepsipeptides.