Phosphoric Acid Derivatives Research Articles

Flame retardant application of a hypophosphite/cyclotetrasiloxane bigroup compound on polycarbonate

ABSTRACTA novel flame retardant aluminum 2,4,6,8‐tetramethyl‐2,4,6,8‐teravinylcyclotetrasiloxane‐hypophosphorous acid (MVC‐AlPi) constituted based on hypophosphite and cyclotetrasiloxane groups was synthesized and characterized through fourier transform infrared and solid‐state nuclear magnetic resonance. The synergistic flame‐retardant behavior and mechanism of MVC‐AlPi/triphenyl phosphate (TPP) in polycarbonate (PC) were investigated. 5%MVC‐AlPi/5%TPP/PC composite got a highest limited oxygen index (LOI) value of 28.4% and passed UL94 V‐0 rating. The cone calorimeter test displayed that 5%MVC‐AlPi/5%TPP system not only inhibited the maximum combustion strength of PC composites, but also suppressed the total combustion reactions, which indicates a good synergistic flame‐retardant effect for MVC‐AlPi/TPP system. The photos of the residues disclosed that the pyrolysis solid fragments by MVC‐AlPi enhanced the residues mechanical strength, and the flexible film from TPP jointly restrained the release of fuels, thereby forming a synergistic barrier effect. The results from X‐ray photoelectron spectroscopy, Raman spectroscopy, and pyrolysis–gas chromatography–mass spectrometry showed TPP mainly exerted quenching effect in gas phase and MVC‐AlPi mostly promoted a charring effect in condensed phase. In addition, the thermal decomposition of MVC‐AlPi also produced some phosphoric acid derivatives which tended to capture benzene ring debris generated by combustion from TPP and to promote the formation of more high‐quality carbon barrier. At the same time, the anti‐impact and tensile strength results from electronic universal testing machine and electronic Izod impact testing machine showed that although the mechanical properties of composites were slightly deteriorated by the addition of MVC‐AlPi/TPP system into PC, the side effect for mechanical properties was still within acceptable limits. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48699.

Highly efficient multielement flame retardant for multifunctional epoxy resin with satisfactory thermal, flame‐retardant, and mechanical properties

Multifunctional epoxy resins with excellent, thermal, flame‐retardant, and mechanical properties are extremely important for various applications. To solve this challenging problem, a novel highly efficient multielement flame retardant (PMSBA) is synthesized and the flame‐retardant and mechanical properties of modified epoxy resins are greatly enhanced without significantly altering their and thermal properties by applying the as‐synthesized PMSBA. The limiting oxygen index value reaches up to 29.6% and could pass the V‐0 rating in the UL‐94 test with even low P content (0.13%). Furthermore, cone calorimetry results demonstrate that 30.3% reduction in the peak heat release rate for the sample with 10.0 wt% PMSBA is achieved. X‐ray photoelectron spectroscopy and scanning electron microscopy indicate that Si‐C, Si‐N, and phosphoric acid derivative can be transformed into a multihole and intumescent char layer as an effective barrier, preserving the epoxy resin structure from fire. More importantly, mechanical properties such as impact strength, tensile strength, and flexural strength are also increased by 63.86%, 33.54%, and 15.65%, respectively, which show the incorporation of PMSBA do not deteriorate the mechanical properties of modified epoxy resins. All the results show that PMSBA is a promising strategy for epoxy resin with satisfactory, thermal, flame‐retardant, and mechanical properties.

Borane and beryllium derivatives of sulfuric and phosphoric acids: Strong inorganic acids

A new class of strong inorganic acids is designed using substitution of the hydrogen atoms of H2SO4 and H3PO4 by BX2 and BeX moieties (X: H, F, Cl, CN, CF3). The acidities of these compounds are assessed by B3LYP/6-311++G(d,p) method in gas phase. These boron and beryllium derivatives are stronger acids than their parents H2SO4 and H3PO4. The acidity of these compounds is attributed to the strong interaction of the oxo group with the Be and B atoms after deprotonation. The electron withdrawing groups enhance the acidity so that a superacid, (B(CF3))2HPO4, with ΔHacid value of 255.5 kcal mol−1 was obtained. In the neutral compounds, Be atom interacts with two oxygen atoms simultaneously to form a four-membered ring while the acyclic isomers of boron derivatives are more stable. However, in the negatively charged conjugated bases, both B and Be atoms interact with two oxygen atoms to form cyclic structures.

ε-Caprolactone: Activated monomer polymerization; controversy over the mechanism of polymerization catalyzed by phosphorus acids (diarylhydrogen phosphates). Do acids also act as initiators?

Whenever Activated Monomer Mechanism (AMM) is involved in cationic ring-opening polymerization of cyclic esters, giving biodegradable polymers, catalysts and initiators are used. In some studies of AMM polymerization of ε-caprolactone (CL), without external initiator added, it was proposed that protonic catalysts are initiating themselves. We have shown by DOSY and other analytical methods for derivatives of phosphoric acid (claimed to act also as initiators) that these catalysts are not initiating polymerization and are separate from macromolecules. Traces of water are initiators. Understanding the role of catalysts in the bulk polymerization of CL allowed preparation of poly(ε-caprolactone) with Mn up to 140,000, for the first time over 105 in AMM.

Aliphatic Long-Chain Polypyrophosphates as Biodegradable Polyethylene Mimics.

Biodegradable polyethylene mimics have been synthesized by the introduction of pyrophosphate groups into the polymer backbone, allowing not only hydrolysis of the backbone but also further degradation by microorganisms. Because of cost, low weight, and good mechanical properties, the use of polyolefins has increased significantly in the past decades and has created many challenges in terms of disposal and their environmental impact. The durability and resistance to degradation make polyethylene difficult or impossible for nature to assimilate, thus making the degradability of polyolefins an essential topic of research. The biodegradable polypyrophosphate was prepared via acyclic diene metathesis polymerization of a diene monomer. The monomer is accessible via a three-step synthesis, in which the pyrophosphate was formed in the last step by DCC coupling of two phosphoric acid derivatives. This is the first report of a pyrophosphate group localized in an organic polymer backbone. The polypyrophosphate was characterized in detail by NMR spectroscopy, size exclusion chromatography, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetry. X-ray diffraction was used to compare the crystallization structure in comparison to analogous polyphosphates showing poly(ethylene)-like structures. In spite of their hydrophobicity and water insolubility, the pyrophosphate groups exhibited fast hydrolysis, resulting in polymer degradation when films were immersed in water. Additionally, the hydrolyzed fragments were further biodegraded by microorganisms, rendering these PE mimics potential candidates for fast release of hydrophobic cargo, for example, in drug delivery applications.

Biodegradation of Organophosphorous Pesticide: Chlorpyrifos

At the present time extensive varieties of pesticides are being used but the demand for organophosphorus pesticide is increasing globally to control insect. Chlorpyrifos is a broad spectrum, moderately toxic, chlorinated organophosphate insecticide that is synthetic in origin and is normally ester or thiol derivatives of phosphoric, phosphonic or phosphoramidic acids. The mode of action involves inhibiting acetyl cholinesterase leading to accumulation of acetylcholine causing neurotoxicity. It is being transported by circulation far away from site of application leading to pollution of environment. Due to its persistent in nature, it is not only severely detrimental to the target pests, but also causes toxicity in non-target organisms including humans. It is thus critically important to develop methods to eradicate these pollutants from the environment. Lately, research activities in this area have demonstrated that microorganisms are potential tool in decaying chlorpyrifos into less harmful and non-toxic metabolites through a process known as bioremediation. This article therefore aims at giving an overview of the present status of research and future prospects in bioremediation of chlorpyrifos.

Synthesis of O-tyrosine Phosphorylated Adducts of Methylphosphonic and Phosphoric Acid Derivatives as Reference Compounds for the Analysis of Biomedical Samples

Organophosphorus chemical agents are included in the 1st List of the Annex on Chemicals of the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction (Chemical Weapons Convention, CWC). For the purposes of verification of compliance with the provisions of the CWC, special methods, which are considered the most informative at determining the retrospective effects of organophosphorus toxicants on the body, are necessary. Typical long-lived biomarkers of organophosphate toxic agents are tyrosine phosphorylation products, the presence of which in biomedical samples clearly indicates the exposure to sarin, soman, tabun and V-series agents. We have elaborated methods for the synthesis and isolation of tyrosine adducts derivatives of methylphosphonic and phosphoric acids, used as reference samples. The synthesis scheme included the consecutive protection of carboxyl and amino groups of tyrosine, its O-phosphorylation by the corresponding alkylphosphonates and phosphates, the removal of protective groups with the release of corresponding O-phosphorylated tyrosine adducts. Their purification from im purities was carried out, using column chromatography (SiO2, eluent: dichloromethane/ethyl acetate 1:1). The purity of the obtained products was more than 90 %, so it was possible to involve them in further transformations with the use of catalyst without the threat of its «poisoning». Benzyl and carboxybenzyl protection of phosphorylated L-tyrosines (12–17) was removed by means of catalytic hydrogenation by molecular hydrogen under atmospheric pressure. Target adducts of phosphorylated reagents and L-tyrosin were obtained (63–82 %) in form of crystal white substances, readily soluble in water and ethanol, and poorly – in dichloromethane and acetonitrile

Asymmetric phosphoric acid-catalyzed four-component Ugi reaction.

The Ugi reaction constructs α-acylaminoamide compounds by combining an aldehyde or ketone, an amine, a carboxylic acid, and an isocyanide in a single flask. Its appealing features include inherent atom and step economy together with the potential to generate products of broad structural diversity. However, control of the stereochemistry in this reaction has proven to be a formidable challenge. We describe an efficient enantioselective four-component Ugi reaction catalyzed by a chiral phosphoric acid derivative that delivers more than 80 α-acylaminoamides in good to excellent enantiomeric excess. Experimental and computational studies establish the reaction mechanism and origins of stereoselectivity.

Attacking olefins with chiral acids

Organic Chemistry A little acid can accelerate a wide range of chemical reactions. The advent of chiral phosphoric acid derivatives has been useful for biasing these reactions toward just one of two mirror-image products. For the most part, though, these chiral catalysts have interacted with basic sites such as carbonyl groups. Tsuji et al. now extend asymmetric acid catalysis to simple carbon-carbon double bonds. Their custom imidodiphosphate forms a pocket that orients olefins to achieve mainly intramolecular alkoxylation on just one face after protonation. Science , this issue p. [1501][1] [1]: /lookup/doi/10.1126/science.aaq0445

Activation of olefins via asymmetric Brønsted acid catalysis.

The activation of olefins for asymmetric chemical synthesis traditionally relies on transition metal catalysts. In contrast, biological enzymes with Brønsted acidic sites of appropriate strength can protonate olefins and thereby generate carbocations that ultimately react to form natural products. Although chemists have recently designed chiral Brønsted acid catalysts to activate imines and carbonyl compounds, mimicking these enzymes to protonate simple olefins that then engage in asymmetric catalytic reactions has remained a substantial synthetic challenge. Here, we show that a class of confined and strong chiral Brønsted acids enables the catalytic asymmetric intramolecular hydroalkoxylation of unbiased olefins. The methodology gives rapid access to biologically active 1,1-disubstituted tetrahydrofurans, including (-)-Boivinianin A.

Development of Dipicolylamine-Modified Cyclodextrins for the Design of Selective Guest-Responsive Receptors for ATP.

The construction of supramolecular recognition systems based on specific host–guest interactions has been studied in order to design selective chemical sensors. In this study, guest-responsive receptors for ATP have been designed with cyclodextrins (CyDs) as a basic prototype of the turn-on type fluorescent indicator. We synthesized dipicolylamine (DPA)-modified CyD–Cu2+ complexes (Cu·1α, Cu·1β, and Cu·1γ), and evaluated their recognition capabilities toward phosphoric acid derivatives in water. The UV-Vis absorption and fluorescence spectra revealed that Cu·1β selectively recognized ATP over other organic and inorganic phosphates, and that β-CyD had the most suitable cavity size for complexation with ATP. The 1D and 2D NMR analyses suggested that the ATP recognition was based on the host–guest interaction between the adenine moiety of ATP and the CyD cavity, as well as the recognition of phosphoric moieties by the Cu2+–DPA complex site. The specific interactions between the CyD cavity and the nucleobases enabled us to distinguish ATP from other nucleoside triphosphates, such as guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytidine triphosphate (CTP). This study clarified the basic mechanisms of molecular recognition by modified CyDs, and suggested the potential for further application of CyDs in the design of highly selective supramolecular recognition systems for certain molecular targets in water.

Streamlined asymmetric \u03b1-difunctionalization of ynones

Ynones are a unique class of structural motifs that show remarkable chemical versatility. Chiral ynones, particularly those possessing an α-stereogenic center, are highly attractive templates for structural diversification. So far, only very limited examples have been reported for asymmetric α-functionalization of ynones. Asymmetric double α-functionalization of ynones remains elusive. Here we describe a streamlined strategy for asymmetric α-difunctionalization of ynones. We developed a gold-catalyzed multicomponent condensation reaction from a simple ynone, an amine, and an electrophilic alkynylating reagent to generate a 1,2-dialkynyl enamine, a key stable and isolable intermediate. This intermediate can undergo asymmetric fluorination catalyzed by a chiral phosphoric acid derivative. Chiral ynones with an α-quaternary carbon and containing a fluorine and an alkyne can be synthesized in high yield and high ee. The synthetic utility of this method is demonstrated by the synthesis of enantioenriched tri(hetero)arylmethyl fluorides.

Understanding the phosphoric acid catalysed ring opening polymerisation of β-Butyrolactone and other cyclic esters

A series of phosphoric acid derivatives have been synthesised and their catalytic activity in the ring opening polymerisation of β-Butyrolactone (β-BL), ɛ-caprolactone and rac-lactide probed. Improved synthetic protocols and characterisation data are provided for a range of catalysts substituted with functional groups altering their electron density and pKa. Lower rates are observed for β-BL polymerisations than other aliphatic cyclic esters. By exploring the reaction kinetics and in situ NMR spectroscopy, we show that the activity decreases due to competitive formation of an off-cycle deactivated species through cleavage of catalyst PO bonds.

Design and Function of Supramolecular Recognition Systems Based on Guest-Targeting Probe-Modified Cyclodextrin Receptors for ATP.

In this study, we have developed a rational design strategy to obtain highly selective supramolecular recognition systems of cyclodextrins (CyDs) on the basis of the lock and key principle. We designed and synthesized dipicolylamine (dpa)-modified γ-CyD-Cu2+ complexes possessing an azobenzene unit (Cu·1-γ-CyD) and examined how they recognized phosphoric acid derivatives in water. The results revealed that Cu·1-γ-CyD recognized ATP with high selectivity over other phosphoric acid derivatives. The significant blue shift in the UV-vis spectra and 1H NMR analysis suggested that the selective ATP recognition was based on the multipoint interactions between the adenine moiety of ATP and both the CyD cavity and the azobenzene unit in addition to the recognition of phosphoric moieties by the Cu-dpa complex site. Our unique receptor made it capable of distinguishing ATP from AMP and ADP, revealing the discrimination of even a length of one phosphoric group. This study demonstrates that, compared to conventional recognition systems of CyDs, this multipoint recognition system confers a higher degree of selectivity for certain organic molecules, such as ATP, over their similar derivatives.

Catalytic Enantioselective Synthesis of Tetrahydocarbazoles and Exocyclic Pictet-Spengler-Type Reactions.

A synthetic strategy for the synthesis of chiral tetrahydrocarbazoles (THCAs) has been developed. The strategy relies on two types of 6-exo-trig cyclization of 3-substituted indole substrates. Enantioselective domino Friedel-Crafts-type reactions leading to THCAs can be catalyzed by chiral phosphoric acid derivatives (with up to >99% ee), and the first examples of exocyclic Pictet-Spengler reactions to form THCAs are reported.

Influences of the adsorption state of catalyst on the performance of DS-PEC for visible light driven water splitting

Adsorption state of catalyst on photoanode is an important factor on influencing the performance of dye-sensitized photoelectrochemical cells (DS-PECs) for water splitting. Photoanode TiO2(1+2) was assembled with Ru(bpy)3 phosphoric acid derivative (complex 1) as photosensitizer and complex 2 as water oxidation catalyst to compare with photoanode TiO2(1+3). The photocurrent density of photoanode TiO2(1+3) with catalyst 3 synthesized with only one end fixing on the surface of TiO2 is about four-fold of the photoanode assembled with catalyst 2 fixing with two claws on the surface of TiO2. The phenomenon should be caused by the littery arrangement and shorter distance of catalyst 2 from the active center of catalyst to TiO2 on the surface of semiconductor which led to lowly efficient electron transfer.

Synthesis of Chiral Phosphorous and Phosphoric Acid Derivatives from the Lignans Matairesinol and Conidendrin

Methods for the preparation of phosphites and phosphates from chiral diols based on lignan backbones were developed. Four novel phosphites and one phosphate were synthesized and characterized. Sterically hindered diols showed diastereoselectivity in formations of phosphites, whereas non-hindered diols showed no selectivity.

A Review of Organophosphate Esters in the Environment from Biological Effects to Distribution and Fate.

Organophosphate esters (OPEs) are synthetic phosphoric acid derivatives used in a wide variety of applications including as flame retardants and plasticizers. Their production and usage has increased in recent years, due to the phase-out of other flame retardant formulations (e.g., polybrominated diphenyl ethers). As such, there has been a recent push to understand the global distribution of OPEs and their behaviour in biota. Multiple studies have been published over the last few years pertaining to OPE concentrations in biotic and abiotic environmental compartments, as well as the metabolism of OPEs in biota. This paper aims to provide a brief review of the occurrence and levels of OPEs in the environment, as well as recent developments concerning the elucidation of OPE metabolism in biota.

ChemInform Abstract: Divergent Roles of Urea and Phosphoric Acid Derived Catalysts in Reactions of Diazo Compounds.

Hydrogen-bond-donor catalysts enable a variety of formal insertion reactions of diazo compounds. The role of the catalyst in the reaction system may vary depending on several factors, including the nucleophilicity of the diazo compound and the acidity of the insertion partner. Ureas and phosphoric acid derivatives can offer complementary reactivity patterns when selected as catalysts for selected O–H and S–H insertion reactions of aryl- and diazo-substituted esters.

A PMMA overlayer improving the surface-bound stability of photoanode for water splitting

A PMMA (polymethly methacrylate) oligomer coating photoanode sensitized with the Ru(bpy)3 phosphoric acid derivative 1 as photosensitizer and complex 2 as water oxidation catalyst was assembled for light driven water splitting. A simple and effective method was optimized by immersing the sensitized photoanode into the DCM solution dissolving 2wt% PMMA for 15s. With the decorated photoanode as working electrode, the DS-PEC displayed much better long-term stability, the photocurrent density of which was found to be 0.57mA/cm2 after 200s sustaining light illumination and is four times as high as the undecorated one (0.15mA/cm2).