Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula PH3, classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting fish, due to the presence of substituted phosphine and diphosphane (P2H4). With traces of P2H4 present, PH3 is spontaneously flammable in air (pyrophoric), burning with a luminous flame. Phosphine is a highly toxic respiratory poison, and is immediately dangerous to life or health at 50 ppm. Phosphine has a trigonal pyramidal structure.
phosphine
DOWNLOAD: https://shoxet.com/2vFihX
Phosphines are compounds that include PH3 and the organophosphines, which are derived from PH3 by substituting one or more hydrogen atoms with organic groups.[4] They have the general formula PH3-nRn. Phosphanes are saturated phosphorus hydrides of the form PnHn+2, such as triphosphane.[5] Phosphine, PH3, is the smallest of the phosphines and the smallest of the phosphanes.
Perhaps because of its strong association with elemental phosphorus, phosphine was once regarded as a gaseous form of the element, but Lavoisier (1789) recognised it as a combination of phosphorus with hydrogen and described it as phosphure d'hydrogène (phosphide of hydrogen).[NB 2]
In 1844, Paul Thénard, son of the French chemist Louis Jacques Thénard, used a cold trap to separate diphosphine from phosphine that had been generated from calcium phosphide, thereby demonstrating that P2H4 is responsible for spontaneous flammability associated with PH3, and also for the characteristic orange/brown color that can form on surfaces, which is a polymerisation product.[7] He considered diphosphine's formula to be PH2, and thus an intermediate between elemental phosphorus, the higher polymers, and phosphine. Calcium phosphide (nominally Ca3P2) produces more P2H4 than other phosphides because of the preponderance of P-P bonds in the starting material.
Alternatively, the acid-catalyzed disproportionation of white phosphorus yields phosphoric acid and phosphine. Both routes have industrial significance; the acid route is the preferred method if further reaction of the phosphine to substituted phosphines is needed. The acid route requires purification and pressurizing.
Phosphine is a worldwide constituent of the Earth's atmosphere at very low and highly variable concentrations.[17] It may contribute significantly to the global phosphorus biochemical cycle. The most likely source is reduction of phosphate in decaying organic matter, possibly via partial reductions and disproportionations, since environmental systems do not have known reducing agents of sufficient strength to directly convert phosphate to phosphine.[18]
Phosphine is a precursor to many organophosphorus compounds. It reacts with formaldehyde in the presence of hydrogen chloride to give tetrakis(hydroxymethyl)phosphonium chloride, which is used in textiles. The hydrophosphination of alkenes is versatile route to a variety of phosphines. For example, in the presence of basic catalysts PH3 adds of Michael acceptors. Thus with acrylonitrile, it reacts to give tris(cyanoethyl)phosphine:[26]
For farm use, pellets of aluminium phosphide (AlP), calcium phosphide (Ca3P2), or zinc phosphide (Zn3P2) release phosphine upon contact with atmospheric water or rodents' stomach acid. These pellets also contain agents to reduce the potential for ignition or explosion of the released phosphine. A more recent alternative is the use of phosphine gas itself which requires dilution with either CO2 or N2 or even air to bring it below the flammability point. Use of the gas avoids the issues related with the solid residues left by metal phosphide and results in faster, more efficient control of the target pests.
Because the previously popular fumigant methyl bromide has been phased out in some countries under the Montreal Protocol, phosphine is the only widely used, cost-effective, rapidly acting fumigant that does not leave residues on the stored product. Pests with high levels of resistance toward phosphine have become common in Asia, Australia and Brazil. High level resistance is also likely to occur in other regions, but has not been as closely monitored. Genetic variants that contribute to high level resistance to phosphine have been identified in the dihydrolipoamide dehydrogenase gene.[28] Identification of this gene now allows rapid molecular identification of resistant insects.
Deaths have resulted from accidental exposure to fumigation materials containing aluminium phosphide or phosphine.[29][30][31][32] It can be absorbed either by inhalation or transdermally.[29] As a respiratory poison, it affects the transport of oxygen or interferes with the utilization of oxygen by various cells in the body.[31] Exposure results in pulmonary edema (the lungs fill with fluid).[32] Phosphine gas is heavier than air so it stays near the floor.[33]
Varfolomeev AE, Volkov AI, Eryshkin AV, Malyshev VV, Rasumov AS, Yakimov SS [1992]. Detection of phosphine and arsine in air by sensors based on SnO2 and ZnO. Sensors and Actuators B: Chem 7(1-3):727-729. Abstract.
Both the purported phosphine signal and this new interpretation of the data center on radio astronomy. Every chemical compound absorbs unique wavelengths of the electromagnetic spectrum, which includes radio waves, X-rays and visible light. Astronomers use radio waves, light and other emissions from planets to learn about their chemical composition, among other properties.
In 2017 using the James Clerk Maxwell Telescope, or JCMT, the U.K.-led team discovered a feature in the radio emissions from Venus at 266.94 gigahertz. Both phosphine and sulfur dioxide absorb radio waves near that frequency. To differentiate between the two, in 2019 the same team obtained follow-up observations of Venus using the Atacama Large Millimeter/submillimeter Array, or ALMA. Their analysis of ALMA observations at frequencies where only sulfur dioxide absorbs led the team to conclude that sulfur dioxide levels in Venus were too low to account for the signal at 266.94 gigahertz, and that it must instead be coming from phosphine.
Such considerations were fueled last year by a publication by a group of researchers led by Jane Greaves of Cardiff University, Wales. In the current issue of the journal Nature Astronomy it is under discussion. At the time, the British scientists had analyzed observational data from the radio telescopes JCMT (James Clerk Maxwell Telescopes) and ALMA (Atacama Large Millimeter/submillimeter Array) and reported finding tiny amounts of the gas phosphine, a compound of one phosphorus and three hydrogen atoms, also known as a monophosphane. Greaves and her co-authors ruled out non-biological origins of the gas, such as lightning or meteorites; instead, bacteria would be a possible source, as on Earth.
However, the wavelengths of some types of molecules are very close together. This is the case with phosphine and sulfur dioxide. In addition, atmospheric pressure plays a role. The deeper in the atmosphere the molecules are found, the higher the pressure and the more often the molecules collide with others. This leads to the fact that, in addition to radiation of their characteristic wavelength, they also emit radiation of closely neighboring wavelengths. This makes it difficult to distinguish between molecules with very similar signals.
The researchers cannot rule out the possibility that tiny amounts of phosphine molecules are floating around in the Venus clouds. But the concentrations would be so small that they could not be detected with JCMT and ALMA.
Phosphine, the simplest phosphorus hydride, is a colorless and extremely toxic gas. Some people think it smells like rotting fish; it reminds others of the odor of garlic. In any case, pure phosphine is actually odorless; an impurity, diphosphane (P2H4), is responsible for its foul scent.
Phosphine is a toxic gas that is used in industrial synthesis. In recent years, phosphine was detected in outer space; some scientists suggest that it may be the source of phosphorus in biomoecules. Just in the past week, Jane S. Greaves at Cardiff University and the University of Cambridge (UK) and several colleagues worldwide reported the discovery of phosphine in the clouds that cover the planet Venus. This truly exciting finding was described in detail in major news outlets because of the possible presence of life on the shrouded planet.
Phosphine oxides and related phosphorus-containing functional groups such as phosphonates and phosphinates are established structural motifs that are still underrepresented in today's drug discovery projects, and only few examples can be found among approved drugs. In this account, the physicochemical and in vitro properties of phosphine oxides and related phosphorus-containing functional groups are reported and compared to more commonly used structural motifs in drug discovery. Furthermore, the impact on the physicochemical properties of a real drug scaffold is exemplified by a series of phosphorus-containing analogs of imatinib. We demonstrate that phosphine oxides are highly polar functional groups leading to high solubility and metabolic stability but occasionally at the cost of reduced permeability. We conclude that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist's toolbox.
An elemental result provided may be converted to the desired compound by multiplying the result by the appropriate stoichiometric factor. A 91B report specific to the compound (including the stoichiometric conversion) may by be provided upon request by contacting the laboratory. The stoichiometric factor for phosphine from phosphorus is 1.098.
"It's so obscure," Sara Seager, an astronomer at the Massachusetts Institute of Technology and co-author on the new research, said during a news conference held virtually today (Sept. 14). "No one cares about [phosphine] except for a few very niche people." 2ff7e9595c
Comments