Phosphorus Chemistry Research Articles

Unlocking the C-centered ring-opening of phosphiranium ions for a straightforward entry to functionalized phosphines

Phosphorus chemistry occupies a pivotal position in contemporary organic chemistry but significant synthetic challenges still endure. In this report, a class of electrophilic phosphiranium salts, bearing fluorinated benzyl quaternizing groups, is introduced for the direct synthesis of diversely β-functionalized phosphines. We show that, in comparison with regular quaternary phosphiranium salts, these species display the sought balance of excellent stability and high electrophilic reactivity that allow the unlocking of the C-centered ring-opening reactions with different classes of weak nitrogen-, sulfur- and oxygen protic nucleophiles.

Observations of phosphorus-bearing molecules in the interstellar medium

The chemistry of phosphorus (31P) in space is particularly significant due to the key role it plays in biochemistry on Earth. Utilising radio and infrared spectroscopic observations, several key phosphorus-containing molecules have been detected in interstellar clouds, circumstellar shells, and even extragalactic sources. Among these, phosphorus nitride (PN) was the first P-bearing molecule detected in space, and still is the species detected in the largest number of sources. Phosphorus oxide (PO) and phosphine (PH3) were also crucial species due to their role both in chemical networks and in forming biogenic compounds. The still limited high-angular resolution observations performed so far are shading light on the geometrical distribution of these molecules, which represent crucial insights on their formation processes. Observations have also highlighted the challenges and complexities associated with detecting and understanding phosphorus chemistry in space, owing to the low elemental abundance of P relative to other elements. This review article provides a state-of-art picture of the observational results obtained so far on phosphorus compounds in the interstellar medium. Special attention is given to star-forming regions, and to their implications for our understanding of prebiotic chemistry and the potential for life beyond Earth. Our knowledge of the dominant formation and destruction pathways of the most abundant species has improved, but critical questions remain open, among which: what is (are) the main phosphorus carrier(s) in space? Upcoming new facilities are expected to contribute significantly to this field, offering opportunities to both detect new phosphorus-bearing molecules and enlarge the number of sources in which the chemistry of P can be studied. The synergy between observations, theoretical models, laboratory experiments, and computational chemistry is mandatory to significantly progress in our comprehension of the chemistry of this important but poorly studied chemical element.

PO and PN in the Envelope of VY Canis Majoris: Elucidating the Chemistry and Origin of Phosphorus

The J = 5.5 → 4.5 and J = 5 → 4 transitions of PO and PN, respectively, have been imaged in the envelope of hypergiant star VY Canis Majoris (VY CMa) using the Atacama Large Millimeter/submillimeter Array with angular resolutions of 0.″2 and 1.″5 and data from the Submillimeter Telescope of the Arizona Radio Observatory. These maps are the first high-fidelity images of PO and PN in a circumstellar envelope. Both molecules are primarily present in a spherical, star-centered region with a radius ∼60 R * (0.″5), indicating formation by LTE chemistry and then condensation into grains. PN, however, shows additional, fan-shaped emission 2″ southwest of the star, coincident with dust features resolved by Hubble Space Telescope (HST), as well as four newly identified distinct structures 1″–2″ toward the north, east, and west (Cloudlets I–IV), not visible in HST images. The “SW Fan” and the cloudlets are also prominent in the J = 5.5 → 4.5 transition of NS. The correlation of PN with NS, SiO, and dust knots in the SW Fan suggests a formation in shocked gas enhanced with nitrogen. Excess nitrogen is predicted to favor PN synthesis over PO. Abundances for PN and PO in the spherical source are f ∼ 4.4 × 10−8 and 1.4 × 10−7, respectively, relative to H2. Given a cosmic abundance of phosphorus, an unusually high fraction (∼35%) is contained in PO and PN. Alternatively, the stellar winds may be enriched in P (and N) by dredge-up from the interior of VY CMa.

6-Plex Tandem Phosphorus Tags (TPT) for Accurate Quantitative Proteomics.

Isobaric chemical labeling is a widely used strategy for high-throughput quantitative proteomics based on mass spectrometry. However, commercially available reagents have high costs in applications as well as the sensitivity limitations for detection of the trace protein samples. Previously, we developed a 2-plex isobaric labeling strategy based on phosphorus chemistry for ultrasensitive proteome quantification with high accuracy. In this work, 6-plex tandem phosphorus tags (TPT) were developed with 3-fold increase in the multiplexing quantitative capacity compared to the 2-plex isobaric phosphorus reagents introduced previously. High isotope enrichment of 18O labeling was incorporated into the phosphoryl group with three exchangeable oxygen atoms by using commercially available H218O. The combinational incorporations of 18O atom in reporter ions and balance group set up the low-cost foundation for development of multiplex TPT reagents. The novel 6-plex TPT reagents could produce phosphoramidate as unique reporter ions with approximately 1 Da mass difference and thus enable 6-plex quantitative analysis in high-resolution ESI-MS/MS analysis. Using HeLa cell tryptic peptides, we concluded that 6-plex TPT reagents could facilitate large-scale accurate quantitative proteomics with very high labeling efficiency.

Manipulation of Linked Phosphorus Chemistry to Enhance the Battery Performance of Phenazine‐Based Porous Polymers

AbstractOrganic p‐type cathodes have captured increasing attention for lithium‐organic batteries due to their high voltage output. However, because of the low electronic and ionic conductivity, the p‐type organic electrode materials often show sluggish reaction kinetics and hence low capacities and poor cyclability. In this work, three conjugated polymers (Pz‐TPPO, Pz‐TPPS, and Pz‐TPP) based on p‐type phenazine linked with triphenyl phosphine are reported with different chemical modifications of phosphorus atom. Through oxidation and sulfuration of phosphorus atoms, the electron‐accepting property strength is increased, resulting in higher electronic conductivity of Pz‐TPPO and Pz‐TPPS. It is also found that the P═O unit in Pz‐TPPO exhibits stronger Li+ coordination, which can bring anions into close proximity to the redox centers, further improving the anion shuttling during charge and discharge. All these lead to the best lithium‐organic battery performance of Pz‐TPPO, such as high voltage output (3.1–3.9 V), high reversible specific capacity (149 mAh g−1 at 0.2 A g−1) and excellent cycle stability. The potential application has also been demonstrated in Pz‐TPPO//graphite full battery. This work provides a novel strategy for designing donor–acceptor (D–A) conjugated polymer by simple phosphorus modification toward high‐performance organic batteries.

Deep Search for Phosphine in a Prestellar Core

Understanding in which chemical forms phosphorus exists in star- and planet-forming regions and how phosphorus is delivered to planets are of great interest from the viewpoint of the origin of life on Earth. Phosphine (PH3) is thought to be a key species to understanding phosphorus chemistry, but never has been detected in star- and planet-forming regions. We performed sensitive observations of the ortho-PH3 10 − 00 transition (266.944 GHz) toward the low-mass prestellar core L1544 with the Atacama Compact Array stand-alone mode of the Atacama Large Millimeter/submillimeter Array. The line was not detected down to 3σ levels in 0.07 km s−1 channels of 18 mK. The nondetection provides the upper limit to the gas-phase PH3 abundance of 5 × 10−12 with respect to H2 in the central part of the core. Based on the gas-ice astrochemical modeling, we find the scaling relationship between the gas-phase PH3 abundance and the volatile (gas and ice with larger volatility than water) P elemental abundance for given physical conditions. This characteristic and well-constrained physical properties of L1544 allow us to constrain the upper limit to the volatile P elemental abundance of 5 × 10−9, which is a factor of 60 lower than the overall P abundance in the interstellar medium. Then the majority of P should exist in refractory forms. The volatile P elemental abundance of L1544 is smaller than that in the coma of comet 67P/C-G, implying that the conversion of refractory phosphorus to volatile phosphorus could have occurred along the trail from the presolar core to the protosolar disk through, e.g., sputtering by accretion/outflow shocks.

Quantum dynamics of the P(2D) + H2 (X1[formula omitted]) → PH (X3Σ-) + H(2S) reaction

The title reaction is thought to be important for the astronomical PO formation, which may contribute to the generation of bioavailable H3PO3. Using quasi-classical trajectory (QCT) method, the state-specified (v = 0, j = 0) rate constant of this reaction was calculated. The comparison with previous temperature-averaged QCT rate constant shows that the effect of ro-vibrational excitation is relatively small below 2000 K. Then, the time-dependent wave packet (TDWP) method was applied to investigate the quantum reaction mechanisms, obtaining the state-specified (v = 0, j = 0) reaction probability, integral cross sections and rate constants. The number of partial waves and the integral interval of collision energy considered were rigorously tested to ensure the convergence of the TDWP rate constant below 2000 K. The TDWP rate constant agrees better to the latest experimental results at 291 to 685 K than those from the two QCT calculations. Also, the TDWP calculations can produce relatively reliable rate constants at 700 to 2000 K, where the Arrhenius formula fitted by experimental results ignores the temperature dependence of the activation energy. The calculated rate constants are helpful for modelling the phosphorus chemistry and determining the abundances of the P-bearing species in interstellar media (ISM).

Synthesis of Mixed Phosphonate Esters and Amino Acid-Based Phosphonamidates, and Their Screening as Herbicides.

While organophosphorus chemistry is gaining attention in a variety of fields, the synthesis of the phosphorus derivatives of amino acids remains a challenging task. Previously reported methods require the deprotonation of the nucleophile, complex reagents or hydrolysis of the phosphonate ester. In this paper, we demonstrate how to avoid these issues by employing phosphonylaminium salts for the synthesis of novel mixed n-alkylphosphonate diesters or amino acid-derived n-alkylphosphonamidates. We successfully applied this methodology for the synthesis of novel N-acyl homoserine lactone analogues with varying alkyl chains and ester groups in the phosphorus moiety. Finally, we developed a rapid, quantitative and high-throughput bioassay to screen a selection of these compounds for their herbicidal activity. Together, these results will aid future research in phosphorus chemistry, agrochemistry and the synthesis of bioactive targets.

The radiative association of PO/PH+ and the photodissociation of PH+

The potential energy curves (PECs) and transition dipole moments (TDMs) of PH+ and PO are computed with the multireference configuration interaction method, and the cross-sections for the radiative association (RA) of PH+ and PO, which is the most efficient way to form the ground states, are presented via the quantum mechanical (QM) theory and computed using ab initio molecular data. The thermal rate coefficients are also expressed and fitted with the standard formula kT=AT300αe−βT in the range of 10 K–15,000 K. Meanwhile, the photodissociation, that is the inverse process of RA for PH+, is also studied, including eight photodissociation channels for the computation of state-resolved cross-sections. Careful comparisons with the Leiden Observatory database are made. Considering the cross-sections mentioned above, the local thermodynamic equilibrium cross-sections at the temperatures of 0, 500, 1,000, and 2,000 K are also shown. We expect the results to be helpful for studies of phosphorus chemistry in the interstellar medium and planetary atmospheres.

Phosphinidenes: Fundamental Properties and Reactivity.

Phosphinidenes are heavy congeners of nitrenes that have been broadly used as in situ reagents in synthetic phosphorus chemistry and also serve as versatile ligands in coordination with transition metals. However, the detection of free phosphinidenes is largely challenged by their high reactivity and also the lack of suitable synthetic methods, rendering the knowledge about the fundamental properties of this class of low-valent phosphorus compounds limited. Recently, an increasing number of free phosphinidenes bearing prototype structural and bonding properties have been prepared for the first time, thus enabling the exploration of their distinct reactivity from the nitrene analogues. This Concept article will discuss the experimental approaches for the generation of the highly unstable phosphinidenes and highlight their distinct reactivity from the nitrogen analogues so as to stimuate future studies about their potential applications in phosphorus chemistry.

Molecular Layer Deposition of Metal Phosphonates: A New Class of Hybrid Coating Layers

Atomic layer deposition (ALD) is a vapor phase thin film deposition technique where materials can be grown atom-by-atom in a layer-by-layer manner. Over the course of just few years, it has become to be one of the most sophisticated methods of producing high quality thin films with control at the sub-nanometer scale. Molecular layer deposition (MLD) is a variant of ALD where molecular fragments are intentionally built into the growing films.MLD is one of the techniques which allows to grow organic-inorganic hybrid materials with thickness control at sub-nanometer level.1 Nowadays, organic-inorganic hybrid materials have been found to attract a lot of attention because of their distinctive properties obtained by combining chemical and physical properties of organic and inorganic segments. Numerous hybrid materials have been synthesized by MLD over the time; however, commercial application of those materials are still a challenge due to their hydrolytic instability in most cases. Perhaps, the most widely used hybrid materials in our daily life is polysiloxanes, or commonly called as silicones, a silicon-based hybrid material . The hydrolytic stability of Si-C and Si-O-Si bonds is the main reason of their practical usage as hybrid materials. Similarly, organophosphorus compounds are an important class of materials because they offer several alternatives to silicon-based linking in the field of hybrid materials. Most of the hybrid films produced by MLD technique contain C, O, N, and S elements in the organic part. Hybrid materials containing P-atoms are yet to be explored by MLD.Among others, metal phosphonates, in particular, an important class of organophosphorus compound, show promising application covering from ion-exchange, proton conductors, catalysts, sensors, membranes, fire retardants etc.2,3 Examples of metal-organic compounds based on phosphonic acid derivatives can be found in literature stemming several decades back. Phosphonates are widely considered as an effective metal chelating ligand. Their dianionic tetrahedral form (RPO3 -2) enables different modes of coordination with metal which is not possible with the extensively used contemporary carboxylate (RCO2 -2) ligands. P-O-M and P-C linkages are quite stable, and therefore organophosphorous compounds with phosphonate ligands have been used to produce thermally and chemically stable hybrid materials by several other techniques.4 Here, we report the synthesis of novel aluminum phosphonate hybrid layers obtained with MLD method. Trimethyl aluminum (TMA) has been used as the metal source and two different novel phosphonate ester precursors with two different organic groups have been used to grow the aluminum phosphonate layers. The growth characteristics of the layers have been studied by in situ ellipsometry, whereas the as-grown films have been characterized with different ex situ techniques like FTIR, XPS, XRD, SEM and AFM. As-deposited metal phosphonate layers show superior thermal (>500 0C in air) and complete water stability. We believe, this kind of metal phosphonate layers may open up new opportunities in the field of organic-inorganic hybrid coatings for various applications. Meng, X. J. Mater. Chem. A 5, 18326–18378 (2017).Goura, J. & Chandrasekhar, V. Chem. Rev. 115, 6854–6965 (2015).Zhu, Y.-P., Yuan, Z.-Y. & Alshareef, H. N. ACS Materials Lett. 2, 582–594 (2020).Vioux, A., Le Bideau, J., Mutin, P. H. & Leclercq, D. New Aspects in Phosphorus Chemistry IV 145–174 (Springer Berlin Heidelberg, 2004).

Phosphorus Chemistry at the Roots of Bioenergetics: Ligand Permutation as the Molecular Basis of the Mechanism of ATP Synthesis/Hydrolysis by FOF1-ATP Synthase.

The integration of phosphorus chemistry with the mechanism of ATP synthesis/hydrolysis requires dynamical information during ATP turnover and catalysis. Oxygen exchange reactions occurring at β-catalytic sites of the FOF1-ATP synthase/F1-ATPase imprint a unique record of molecular events during the catalytic cycle of ATP synthesis/hydrolysis. They have been shown to provide valuable time-resolved information on enzyme catalysis during ATP synthesis and ATP hydrolysis. The present work conducts new experiments on oxygen exchange catalyzed by submitochondrial particles designed to (i) measure the relative rates of Pi-ATP, Pi-HOH, and ATP-HOH isotope exchanges; (ii) probe the effect of ADP removal on the extent of inhibition of the exchanges, and (iii) test their uncoupler sensitivity/resistance. The objectives have been realized based on new experiments on submitochondrial particles, which show that both the Pi-HOH and ATP-HOH exchanges occur at a considerably higher rate relative to the Pi-ATP exchange, an observation that cannot be explained by previous mechanisms. A unifying explanation of the kinetic data that rationalizes these observations is given. The experimental results in (ii) show that ADP removal does not inhibit the intermediate Pi-HOH exchange when ATP and submitochondrial particles are incubated, and that the nucleotide requirement of the intermediate Pi-HOH exchange is adequately met by ATP, but not by ADP. These results contradicts the central postulate in Boyer's binding change mechanism of reversible catalysis at a F1 catalytic site with Keq~1 that predicts an absolute requirement of ADP for the occurrence of the Pi-HOH exchange. The prominent intermediate Pi-HOH exchange occurring under hydrolytic conditions is shown to be best explained by Nath's torsional mechanism of energy transduction and ATP synthesis/hydrolysis, which postulates an essentially irreversible cleavage of ATP by mitochondria/particles, independent from a reversible formation of ATP from ADP and Pi. The explanation within the torsional mechanism is also shown to rationalize the relative insensitivity of the intermediate Pi-HOH exchange to uncouplers observed in the experiments in (iii) compared to the Pi-ATP and ATP-HOH exchanges. This is shown to lead to new concepts and perspectives based on ligand displacement/substitution and ligand permutation for the elucidation of the oxygen exchange reactions within the framework of fundamental phosphorus chemistry. Fast mechanisms that realize the rotation/twist, tilt, permutation and switch of ligands, as well as inversion at the γ-phosphorus synchronously and simultaneously and in a concerted manner, have been proposed, and their stereochemical consequences have been analyzed. These considerations take us beyond the binding change mechanism of ATP synthesis/hydrolysis in bioenergetics.

Phosphorus Chemistry in Plant Ash: Examining the Variation across Plant Species and Compartments

Phosphorus Chemistry in Plant Ash: Examining the Variation across Plant Species and Compartments

A Theoretical Approach to the Complex Chemical Evolution of Phosphorus in the Interstellar Medium

The study of phosphorus chemistry in the interstellar medium has become a topic of growing interest in astrobiology because it is plausible that a wide range of P-bearing molecules were introduced in the early Earth by the impact of asteroids and comets on its surface, enriching prebiotic chemistry. Thanks to extensive searches in recent years, it has become clear that P mainly appears in the form of PO and PN in molecular clouds and star-forming regions. Interestingly, PO is systematically more abundant than PN by factors typically of ∼1.4–3, independently of the physical properties of the observed source. In order to unveil the formation routes of PO and PN, in this work we introduce a mathematical model for the time evolution of the chemistry of P in an interstellar molecular cloud and analyze its associated chemical network as a complex dynamical system. By making reasonable assumptions, we reduce the network to obtain explicit mathematical expressions that describe the abundance evolution of P-bearing species and study the dependences of the abundance of PO and PN on the system’s kinetic parameters with much faster computation times than available numerical methods. As a result, our model reveals that the formation of PO and PN is governed by just a few critical reactions, and fully explains the relationship between PO and PN abundances throughout the evolution of molecular clouds. Finally, the application of Bayesian methods constrains the real values of the most influential reaction rate coefficients making use of available observational data.

Reaction dynamics of P(4S) + O2(X3Σ−g) → O(3P) + PO(X2Π) on a global CHIPR potential energy surface of PO2(X2A1): implications for atmospheric modelling

Abstract. The reaction dynamics of P(4S) + O2(X3Σg-) → O(3P) + PO(X2Π) are thought to be important in atmospheric and interstellar chemistry. Based on the state-of-the-art ab initio energy points, we analytically constructed a global potential energy surface (PES) for the ground-state PO2(X2A1) using the combined-hyperbolic-inverse-power-representation (CHIPR) method. A total of 6471 energy points were computed by the multireference configuration interaction method with the Davidson correction and aug-cc-pV5Z basis set. The analytical CHIPR PES reproduces ab initio energies accurately with a root-mean-square deviation of 91.5 cm−1 (or 0.262 kcal mol−1). The strongly bound valence region of the PES has complicated topographical features with multiple potential wells and barriers. The attributes of the important intermediates are carefully validated with our geometry optimization results, as well as previous experimental and computational results. Finally, the reaction probability, integral cross sections, and rate constants for P(4S) + O2(X3Σg-) → O(3P) + PO(X2Π) are calculated using the quasi-classical trajectory and time-dependent wave packet methods. The trends of probability and integral cross section versus the collision energy can be divided into three stages, which are governed by the entrance barriers or exothermicity of the reaction. The rate constant demonstrates strong Arrhenius linear behaviour at relatively low temperatures but deviates from this pattern at high temperatures. The calculated cross sections and rate constants are helpful for modelling the phosphorus chemistry in atmospheric and interstellar media.

Uncertainty in phosphine photochemistry in the Venus atmosphere prevents a firm biosignature attribution

Context. The possible detection of phosphine (PH3) in the clouds of Venus has raised the question as to which processes could produce such large abundances of PH3. Previous studies suggested that abiotic processes including photochemical production cannot explain the claimed PH3 concentrations. However, the photochemistry of phosphorus-bearing species in the atmosphere of Venus is not well known. Aims. We aim to assess the abiotic production of PH3 considering the effect of uncertainties in the chemical rate coefficients of phosphorus-containing reactions. Methods. Using a photochemical column model, we simulated Venus-like conditions and varied the chemical rate coefficients with a Monte Carlo (MC) approach in order to estimate the associated error in the PH3 abundances throughout the atmosphere. Results. Current uncertainties and missing data in photochemical rate coefficients lead to a variation of about six orders of magnitude in the modelled PH3 abundance on Venus, assuming photochemical production of PH3 from tetraphosphorus hexoxide (P4O6) pathways. Our results suggest an abiotically produced upper limit of 2 ppb PH3 between 50 and 60 km. These concentrations are in the range of a recent reanalysis of Atacama Large Millimeter Array (ALMA) data, suggesting planet-averaged abundances in PH3 of 1–4 ppb above 55 km. Future observations of phosphorus monoxide (PO) on Venus would be beneficial for increasing our confidence in assessing PH3 as a biosignature. Conclusions. We conclude that due to the large uncertainties in phosphorus chemistry, even a firm detection of several ppb PH3 in the Venus atmosphere would not necessarily mean a biological origin.

Deoxygenation of Phosphine Oxides by PIII/PV═O Redox Catalysis via Successive Isodesmic Reactions.

Deoxygenation of phosphine oxides is of great significance to synthesis of phosphorus ligands and relevant catalysts, as well as to the sustainability of phosphorus chemistry. However, the thermodynamic inertness of P═O bonds poses a severe challenge to their reduction. Previous approaches in this regard rely primarily on a type of P═O bond activation with either Lewis/Brønsted acids or stoichiometric halogenating reagents under harsh conditions. Here, we wish to report a novel catalytic strategy for facile and efficient deoxygenation of phosphine oxides via successive isodesmic reactions, whose thermodynamic driving force for breaking the strong P═O bond was compensated by a synchronous formation of another P═O bond. The reaction was enabled by PIII/P═O redox sequences with the cyclic organophosphorus catalyst and terminal reductant PhSiH3. This catalytic reaction avoids the use of the stoichiometric activator as in other cases and features a broad substrate scope, excellent reactivities, and mild reaction conditions. Preliminary thermodynamic and mechanistic investigations disclosed a dual synergistic role of the catalyst.

Evaluation of Different Extractants to Estimate Bioavailable Arsenic in Soil

ABSTRACT Owing to the similar chemistry of phosphorus (P) and arsenic (As), sodium bicarbonate (0.5 N NaHCO3) is commonly used to extract plant accessible As in soil. This extractant has neither been tested widely in relation to plant As, nor is this extractant compatible with inductively coupled plasma mass spectrometry (ICP-MS) due to the high concentration of dissolved solid. Subsequently, it is of utmost important to design a suitable chemical extraction method in order to estimate plant available As compatibility with ICP-MS. For this purpose, paired soil and plant samples were collected from paddy fields located in Nadia, West Bengal, India. Soil was extracted with 0.5 M NaHCO3, 0.1 N and 0.5 N phosphoric acid (H3PO4), 0.1 N and 0.5 N sulfuric acid (H2SO4), 0.1 N, 0.5 N, 1.0 N, 1.5 N HNO3 and 0.01 M calcium chloride (CaCl2) solution. Arsenic extracted with NaHCO3, H3PO4 and H2SO4 was determined in hydride generation-atomic absorption spectrophotometer (HG-AAS), while ICP-MS served to determine As extracted from soil with HNO3. Olsen-extractable As in soils ranged from 0.48 to 3.57 mg kg−1 with a mean value of 1.45 mg kg−1. The extractable As content in soil varied from 0.01 to 10.1 mg kg−1 across the extractants. In the case of grain As, 0.1 N H3PO4, 0.5 N NaHCO3 and 1.5 N HNO3 extractable As had distinctly higher correlation coefficients (r = 0.49**, r = 0.47**, r = 0.45**) when compared to other extractants. More or less similar relationships of extractable As were obtained with straw As content like that of rice grain. In view of rapidity of the soil test method for As, 1.5 N HNO3 can be recommended for assessing available As in soil.

Large Uncertainties in the Thermodynamics of Phosphorus (III) Oxide (P4O6) Have Significant Implications for Phosphorus Species in Planetary Atmospheres

Phosphorus (III) oxide (P$_4$O$_6$) has been suggested to be a major component of the gas phase phosphorus chemistry in the atmospheres of gas giant planets and of Venus. However, P$_4$O$_6$'s proposed role is based on thermodynamic modeling, itself based on values for the free energy of formation of P$_4$O$_6$ estimated from limited experimental data. Values of the standard Gibbs free energy of formation ($\Delta$Go(g)) of P$_4$O$_6$ in the literature differ by up to ~656 kJ/mol, a huge range. Depending on which value is assumed, P$_4$O$_6$ may either be the majority phosphorus species present or be completely absent from modeled atmospheres. Here, we critically review the literature thermodynamic values and compare their predictions to observed constraints on P$_4$O$_6$ geochemistry. We conclude that the widely used values from the NIST/JANAF database are almost certainly too low (predicting that P$_4$O$_6$ is more stable than is plausible). We show that, regardless of the value of $\Delta$Go(g) for P$_4$O$_6$ assumed, the formation of phosphine from P$_4$O$_6$ in the Venusian atmosphere is thermodynamically unfavorable. We conclude that there is a need for more robust data on both the thermodynamics of phosphorus chemistry for astronomical and geological modeling in general and for understanding the atmosphere of Venus and the gas giant planets in particular.

Review of Phosphorus Chemistry in the Thermal Conversion of Biomass: Progress and Perspectives

Phosphorus is vital for all life, which means that phosphorus is present in all biomass to some extent. Some types of biomass, such as certain agricultural residues, animal biomass, and sewage sludge, contain high levels of phosphorus. In thermal conversion of biomass, high levels of phosphorus can cause various operational problems. Extensive work has been carried out to understand the phosphorus chemistry taking place at higher temperatures. However, until now, knowledge about transformation chemistry and fate of phosphorus during thermal conversion of biomass was not easily accessible in one place. In this work, the outcome of an extensive literature review has been summarized. First, an introduction to the role of phosphorus in biomass, and in what forms it may be present, is given. Different analytical techniques relevant for characterization of phosphorus in biomass, biomass char, and biomass ash are described. A classification of phosphorus-rich biomass is proposed, and the potential of different phosphorus-rich biomass types is presented. To provide a common basis for the field of high-temperature phosphorus chemistry, fundamental chemistry relevant for thermal conversion of biomass is first discussed. This includes the gas phase chemistry and reaction pathways of light phosphorus species, pyrolysis, and combustion of organophosphorus compounds, and solid, liquid, and gaseous interactions with other ash-forming elements. Thereafter, an in-depth review of phosphorus transformations in biomass, including decomposition of organic phosphorus, ash transformations in the condensed phase, release to the gas phase, and formation of particulate matter in the flue gas follows. Finally, the review covers research focusing on phosphorus in different application aspects, such as the use of phosphorus as an additive to mitigate operational problems related to slag and deposit formation, the behavior of phosphorus in fluidized bed technologies, corrosion, and the deactivation of SCR catalysts.