: From the Stars to Land & Sea

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Citation Cummins, Christopher C. “Phosphorus: From the Stars to Land & Sea.” Daedalus 143, no. 4 (October 2014): 9–20.

As Published http://dx.doi.org/10.1162/DAED_a_00301

Publisher MIT Press

Version Final published version

Citable link http://hdl.handle.net/1721.1/92509

Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. Phosphorus: From the Stars to Land & Sea

Christopher C. Cummins

Abstract: The chemistry of the element phosphorus offers a window into the diverse ½eld of . Fundamental investigations into some simple molecules containing phosphorus reveal much about the rami½cations of this element’s position in the and that of its neighbors. Addition - ally, there are many phosphorus compounds of commercial importance, and the surrounding this element resides at a crucial nexus of natural resource stewardship, technology, and modern . Questions about our sources of phosphorus and the applications for which we deploy it raise the provocative issue of the human role in the ongoing depletion of phosphorus deposits, as well as the transfer of phos- phorus from the land into the seas.

Inorganic chemistry can be de½ned as “the chem- istry of all the elements of the periodic table,”1 but as such, the ½eld is impossibly broad, encompassing everything from to materials sci- ence and enzymology. One way to gain insight into and appreciate the rapidly moving and diverse ½eld of inorganic chemistry is to view the science from the perspective of the elements themselves, since they are the basic ingredients for assembling - cules or materials–and indeed, all matter, living or inanimate. Although phosphorus may be less cele- brated than carbon or , it joins those ele- ments (along with , , and ) to constitute the six “biogenic elements” (those needed CHRISTOPHER C. CUMMINS,a Fellow of the American Academy in large quantities to make living organisms; see Fig - 2 since 2008, is Professor of Chemis - ure 1). Let us take a look at some of the issues that try at the Massachusetts Institute of arise in inorganic chemistry from the perspective of Technology. His research focuses on phosphorus, illustrating in the process the notion innovating new methods of in or- that each element has its own story to tell. gan ic synthesis, as well as the syn - the sis of new simple substances. His work has recently appeared in Inor - Many phosphorus-containing chemical com- ganic Chemistry, Science, Journal of the pounds are commercially valuable and have interest- 3 American Chemical Society, and Chem - ing or important applications. Lithium hexafluoro - ical Science, among other journals. , for example, is the electrolyte in common

© 2014 by Christopher C. Cummins Published under a Creative Commons Attribution 3.0 Unported (CC BY 3.0) license doi:10.1162/DAED_a_00301

9 Phosphorus: Figure 1 From the Periodic Table with , Including Biogenic Elements, Above the Stair-Step Line Stars to Land & Sea

Biogenic elements are H, C, N, O, P, S in the “nonmetals” region of the periodic table, indicated by the heavy line. Source: Adapted from a graphic found on http://www.openclipart.org.

lithium-ion batteries, which are used in phorus if is not even present in consumer electronics (such as laptops) the products, such as lithium hexafluoro- and automotive applications.4 So how is phosphate, that are the target of synthesis? it made? The synthesis route begins with These industry standard processes suggest the white form of elemental phosphorus, there is room for improvement: if manu- a simple molecular form of the element facturers eliminated the use of chlorine P consisting of tetrahe dral 4 molecules in the synthesis of important phosphorus (Figure 2).5 White phosphorus is com- compounds in which chlorine is absent, bined with elemental chlorine in order to both hazards and waste would be signi½- bring the phosphorus to the correct oxi- cantly reduced. dation state (+5), and then, in a second Because our research has shown that it is step, chloride is replaced by fluoride. indeed possible to derive organo-phospho- This process is also frequently used to rus compounds directly from white phos- synthesize many organo-phosphorus com- phorus, this is an opportunity for inor- pounds that are important components of ganic chemistry to improve the safety and catalysts used in the .6 ef½ciency of the process. In these applications, again, white phos- In one advance, we showed that phospho- phorus is ½rst oxidized using chlorine, and rus-carbon bonds can be generated by then the chloride provides the basis for the using white phosphorus together with a formation of carbon-phosphorus bonds.7 source of organic radicals.9 Each of the six But notably, elemental chlorine is hazard- phosphorus-phosphorus bonds present in ous to use and ship, and environmental a molecule of white phosphorus absorbs groups have called for an outright ban on two organic radicals in the process of being 8 it. So why use chlorine to oxidize phos- broken; each P4 tetrahedron is broken

10 Dædalus, the Journal ofthe American Academy of Arts & Sciences Figure 2 Christopher P C. Cummins Tetrahedral Arrangement of Atoms in a 4 (White Phosphorus) Molecule

Source: Generated by the author using the platon program. See A. L. Spek, “Single- Valida- tion with the Program platon,” Journal of Applied Crystallography 36 (2003): 7–13. completely apart, and each phosphorus in a wide variety of structural arrange- atom becomes incorporated into a freshly ments, all of which are networks exclusive- formed organo-phosphorus compound. ly based upon phosphorus-phosphorus Our method for developing this new sin gle bonds, three for every phosphorus pro cess was derived from basic inquiries node. The variant known as red phospho- into phos phorus’s relationship to the ele- rus, for example, has cages of phosphorus ments neighboring it on the periodic ta ble. atoms connected into linear tubes (see Fig- Phosphorus is immediately beneath nitro- ure 3),12 which in turn are cross-linked to - gen on the periodic table, suggesting that geth er to form a polymeric net work. these el e ments should have some sim ilar i - Knowing this, we were inspired to ask: ties in their chemical properties. Then why, can we design and synthesize a molecule we won dered, was it the case that, while that would be prone to a fragmentation re- Earth’s atmosphere consists mainly of ac tion wherein one of the fragments pro- N P triply-bonded 2 molecules, a similar di - duced would be the diatomic molecule 2? atom ic molecular form of phosphorus is If we could, we would have the opportu- neither prevalent nor even particularly sta- nity to study the properties and chemical b l e ? 10 Part of the answer is that nitrogen characteristics of an all-phosphorus mol- is unusual because the stability of its mul- ecule structurally analogous to the main tiple bond far exceeds that of the sum of constituent of Earth’s atmosphere. In our an equivalent number (three) of its single ½rst attempt to produce it, the selected de- bonds. So the only stable form of elemen- sign incorporated a feature patterned after tal nitrogen is the diatomic molecular form the reaction used to inflate an automobile floating innocuously about in the atmos- airbag in the event of a collision, a process phere we breathe; in contrast, phosphorus that rapidly generates nitrogen gas from a (like its diagonal relative, carbon)11 exists precursor. Our target molecule em -

143 (4) Fall 2014 11 Phosphorus: Figure 3 From the Arrangement of Atoms in One of the Representative Structural Forms of Red Phosphorus Stars to Land & Sea

The box encloses one crystallographic unit . Source: Generated by the author using crystallographic coordi- nates from M. Ruck et al., “Fibrous Red Phosphorus,” An gewandte Chemie International Edition 44 (2005), doi:10.1002/ anie.200503017.

bed ded a moiety into the generation should not matter. Could there P sta bilizing environment of a be a way to access the 2 molecule by start- complex (niobium is a transition ; ing from a stable form of the element, rath- it forms complexes by arranging sets of er than from an exotic niobium complex? molecules or –called ligands–around We found the suggestion in a lightly cited itself ), from which it could be released by 1937 paper that the photochemical conver- a stimulus of mild heating.13 Carrying out sion of white phosphorus into the red form the fragmentation reaction in the presence of the element may occur with P2 as the of other molecules permitted the mapping key intermediary, which is initially gener - of the reactivity patterns of diatomic phos - ated and subsequently polymerizes.14 phorus. One important result was the dis - We found by experiment (see Figure 5) that P covery that 2 easily undergoes addition to the addition of methyl isoprene to a solu- unsaturated organic molecules, such as 1,3- tion of white phosphorus during irradia- cyclohexadiene (see Figure 4). tion both inhibits the production of red If diatomic molecular phosphorus is in - phos phorus and yields molecules in the deed capable of direct combination with same class of organo-phosphorus com- organic molecules, then the means of its pounds that we studied earlier in connec-

12 Dædalus, the Journal ofthe American Academy of Arts & Sciences Figure 4 Christopher P C. Cummins A Niobium Complex that Can Act as an “Eliminator” of 2 under Thermal Fragmentation neat neat

65 °C

P In the depicted sequence, transient 2 (not observed) combines with two molecules of 1,3-cyclohexadiene resulting in four new P-C single bonds in the stable ½nal product (shown both as a line drawing and in a thermal ellipsoid representation from a single-crystal X-ray diffraction analysis). Abbreviations: tBu is tert-butyl, Ar is aryl (spe - M C H M ci½cally 3,5- e2 6 3), and es* is supermesityl. Source: Adapted from material published in N. A. Piro, J. S. Figueroa, J. T. McKellar, and C. C. Cummins, “Triple-Bond Reactivity of Diphos phorus Molecules,” Science 313 (2006), doi: 10.1126/science.1129630.

A tion with niobium-mediated access to di - s4 mole cules, one heats grey arse - phosphorus molecules.15 Hence, in effect nic (which has a layered sheet structure and in principle, we have shown that in rem iniscent of graph ite or black phospho - certain cases the hazardous and wasteful rus) to about 550 degrees C while flowing a use of chlorine in the synthesis of organo- carrier gas over it. The As4 molecules, en- phosphorus com pounds can be replaced trained in the carrier gas, can be led into a with a process rely ing on ultraviolet radia- solvent and used for reaction chemistry be- tion. fore re-polymer ization to grey can take place. If con densed to a solid on a A After viewing the beautiful tetrahedral cold surface, the s4 condensate is “ molecular form of elemental phosphorus arsenic,” but it cannot be kept. Warming in Figure 2, one might wonder whether this to room temper ature or ex posure to light arrangement of phosphorus is unique to brings about a facile return to the grey this particular element. Arsenic (As) lies form.16 just below phosphorus on the periodic ta- Phosphorus and arsenic lie on either side ble, separated from it by the stair-step line of the divide (marked on Figure 1) separat - dividing the from the nonmetals ing the metals from the non-metals. White (see Figure 1). Once again, the periodicity phosphorus is stable enough that it can be of chemical properties suggests that mol - stored as a pure liquid above its melting ecular arsenic might adopt a similar tet - point of 44 degrees Cand pumped into tank rahedral struc ture to that of phosphorus. cars for shipping; while, conversely, sam- Indeed, it does, but only in the gas phase ples of yellow arsen ic are eva nes cent. We where the molecules are well isolated from therefore wondered: would it be possible one another, or in solution at low temper- to synthesize a stable substance whose tet- ature and in the dark. To generate gas- rahedral mol ecules would be composed of

143 (4) Fall 2014 13 Phosphorus: Figure 5 From the Combination of Phosphorus with Methyl Isoprene under the Action of Ultraviolet Light Stars to Land & Sea

P Methyl isoprene is the precursor to the original synthetic rubber. The reaction mechanism may involve 2 as a reactive photo-generated intermediate.17 Source: Generated by the author using data from Daniel Tofan and Chris - topher C. Cummins, “Photochemical Incorporation of Diphosphorus Units into Organic Molecules,” Angewandte Chemie International Edition 49 (2010), doi:10.1002/anie.201004385.

Figure 6 P A From the Commodity-Chemical 4 Molecule to the Unstable s4 Molecule

commodity chemical ? ? ? unstable

What are the properties of substances composed of tetrahedral molecules of mixed composition? Source: Adapted A P from Brandi M. Cossairt and Christopher Cummins, “Properties and Reactivity Patterns of s 3: An Experimental and Computational Study of 15 Elemental Molecules,” Journal of the American Chemical Society 131 (42) (2009), doi:10.1021/ja906294m.

a mixture of phosphorus and arsenic (see provides a benchmark for theorists work- Figure 6)? To test this idea, we made a ni - ing on the a priori predic tion of properties; obium complex carrying a P33− unit, and heavy elements pose the greatest challenge A P combined this with a source of arsenic in this regard. The elements in the s 3 (3+), effectively knitting together the neu - molecule are packaged together in a 1:3 A P 18 tral s 3 mole cule in a se lective . ratio at the molecular level; and now this The new sub stance turned out to have a substance is readily avail able as a start ing waxy appearance much like that of white material. Substitution of a single nitro gen phosphorus, and it could be puri½ed by atom into the P4 tetrahedron has scarcely sublimation, wherein the pure material is been considered; one possibility involves condensed on to a cold probe. Because of stabiliza tion inside a recently dis covered A P B the volatile nature of s 3, we and our col - spherical 80 molecule that is analogous to C 20 laborators determined its prop erties by a Buckmin sterful lerene ( 60). variety of techniques, including electron diffraction, microwave spectros copy, and To ask why diatomic phosphorus is nei- photoelectron spectro scopy.19 Obtaining ther stable nor prevalent is really to ask a gas-phase property data on a sim ple mol- larger question: why is elemental phospho- ecule containing a heavy element (arsenic) rus not found on Earth as a pure substance,

14 Dædalus, the Journal ofthe American Academy of Arts & Sciences uncombined with other chemical ele- ed great quantities of human , which Christopher ments? It is because elemental phosphorus he concentrated to a paste and subjected to C. Cummins is especially prone to oxidation, a process reductive .) encouraged by Earth’s atmosphere at this Phosphate rock is not only the basis for point in history. Elements that form very the ½ne chemicals industry of phosphorus; stable (such as aluminum, phos pho - it is also the starting point for the (much rus, and ) are not found in uncom- larger) phosphorus side of the in- bined form on our planet unless they can dustry. The “wet process” of puri½cation be formed by biological or geological pro- uses sulfuric to generate phosphoric cesses taking place under anaer obic condi - acid from phosphate rock, after which it tions (as in the case of volcanic sulfur, or can be made into critical such carbon in the form of and diamond). If as monoammonium phosphate, or map. we cannot obtain phosphorus in pure form Around 1940, the human population of our directly by digging it out of the ground, planet began to rise more rapidly than it where do we get it? had previously (since my birth in 1966 the Phosphate rock (also known by its min- population has doubled).25 This critical eral name ) is essentially the rise in population growth coincided with and teeth of ancient marine organisms two important developments in the fertiliz - formed into concentrated deposits where er industry: the worldwide commercial de- long-evaporated seas once stood.21 It is ex- ployment of the Haber-Bosch ammonia tracted through strip and forms synthesis (whereby ammonia for agricul- the basis for the phosphorus ½ne chemicals tural applications is obtained by direct industry. One of the principal methods for combination of the elements hydrogen and white phosphorus22 production is the nitrogen); and the large-scale mining of “thermal process,” which involves use of phosphate rock deposits, mainly for fertil - an , carbon in the form iz er applications. Prior to the mid-twenti- of as a reducing agent, and silica to ab - eth century, humankind had been largely sorb the ions liberated in the heating limited to locally available for process.23 The elemental phosphorus is crop production. Now, ammonia can be thus extracted from the rock in what is es - had in essentially limitless supply by com- sentially an expensive puri½cation process. bining the atmosphere’s inexhaustible sup- Note that most phosphorus-containing ply of nitrogen with hydrogen (which is commercial chemicals contain phospho- currently derived from natural gas by steam rus in the +5 : the same as reforming). Can phosphorus keep up? is found in phosphate rock when it is dug out of the ground. The typical puri½cation Stars are the element factories.26 They process reduces phosphorus’s oxidation con sist mainly of our universe’s lightest state from +5 to zero; however, when it is and most abundant elements: hydrogen converted to other chemicals, chlorine is and helium. Red giants are more evolved often used to return the phosphorus to its stars with an -like layered structure; highest oxidation state (zero back to +5). the most abundant metallic elements, (This method of making white phospho- and nickel, make up their core, and layers rus is, in fact, reminiscent of the one used of progressively lighter elements surround by the alchemist , who made them, moving outward to the surface. El- phosphorus the thirteenth element to be ements heavier than iron and nickel are obtained in pure form.24 In search of the formed by neutron capture when a massive philosopher’s stone, the alchemist collect- star explodes in a , and these (in-

143 (4) Fall 2014 15 Phosphorus: cluding the precious gold sought by the exhausted, leaving behind a legacy of ra - From the alchemist) are of minimal cosmic abun- dioactive phosphogypsum stacks and col - Stars to 30 Land & Sea dance. It is one of the peculiarities of nu - lapsing sinkholes. The term “peak phos- clear physics that nuclei of odd atomic phorus” is now used with reference to the num ber (odd Z) are generally less stable point in time when phosphate rock pro- and less abundant than those of even Z. duction (mining) will inevitably begin to The only stable of phosphorus is taper off.31 Current estimates place peak 31P(Z = 15), and the 31Pnucleus is the prod - phosphorus some time later in the twenty- uct of an extremely improbable sequence ½rst century. of nuclear reactions (the ½nal reaction in Off the coast of Brittany, France, there the sequence converts 31Si into 31P by pro - are sometimes blooms of marine algae vast ton capture), only taking place during an enough to be visible from space.32 Brit- explosive burning phase in the core tany is a livestock-producing region where of massive, hot stars.27 Accordingly, the large amounts of phosphate from feed is cosmic abundance of phosphorus is lower transferred to the ground water and ulti- –by orders of magnitude–than that of the mately to the ocean. This perfectly illus- other ½ve biogenic elements. Indeed, to trates two consequences of the large-scale quote astrobiologist Douglas Whittet: mining of phosphate rock and industrial- “The only biogenic element present in the ized agricultural activity: ½rst, we are de- (and in biological tissue gen- pleting the concentrated of this erally) at a concentration substantially key ; second, its dispersal into the above its solar abundance is P. If one were world’s oceans can have negative effects on to attempt to place an upper limit on the marine , chiefly by causing eu- total biomass present in the Universe at trophication through overgrowth of cer- large, on the basis of cosmic abundances, tain species of phytoplankton. then the critical element would be phos- What can we do to mitigate the move- phorus.”28 This is in keeping with the ob - ment of phosphorus from land to sea? Ef - servation that, in many of the ecosystems forts are being directed at optimizing the on Earth, phosphorus is -limiting. This separation and recovery of phosphorus means that the addition of phosphorus from waste water, which is an important (usually in the form of phosphate) will direction.33 In some countries (such as In- bring about an abrupt bloom of life, since dia and ), the use of toilets that sep- the absence of phosphorus was all that was a rate liquid from solid waste is being adopt- holding it back. ed; phosphate can then be recovered from Our land reserves of phosphorus are ½ - urine as the crystalline struvite, nite. And given the ongoing depletion of while solid waste is composted.34 Pigs can- phosphate rock reserves, it is natural to not digest -derived phosphate because ask what is left, where it is, and how long it of the form in which will last. The U.S. Geological survey indi- store it (see Figure 7), so researchers at the cates that roughly three-quarters of the University of Guelph in Canada developed available reserves are concentrated in Mo - the Enviropig.35 This genetically engi- rocco and Western Sahara.29 Mining loca- neered pig secretes the enzyme in tions in and contain the most its saliva, enabling the pig to digest the signi½cant amount of phosphate rock in plant phosphate, whereupon its excreta are the United States, but these constitute a phosphate-poor, leading to an improve- small percentage of global reserves. And ment in waste water quality. While the Central Florida’s mines have been largely of the Enviropig is the same as that of

16 Dædalus, the Journal ofthe American Academy of Arts & Sciences Figure 7 Christopher Molecular Structure of Phytic Acid C. Cummins

Source: Generated by the author using the program MarvinSketch. Marvin is used for drawing, displaying, and characterizing chemical structures, substructures, and reactions. See ChemAxon, Marvin 6.1.3 (2014), http://www.chemaxon.com. an unmodi½ed pig, concerns about this identify ways of using this limited resource cre ative kind of genetic have that minimize waste, but we acknowledge effectively blocked its adoption thus far. our limited ability to grapple with the con- The chemistry of an element is a fasci- sequences of enormous demand for phos - nating thing, and we have explored several phorus–a markedly limited resource– of the issues that flow naturally from ask- stemming from a rapidly rising human ing questions about where an element population. Phosphorus, therefore, is in - comes from, what we use it for, and how teresting not only for its chemistry but we might gain an improved understanding also in light of the rich texture of its larg- of it. Motivated to study phosphorus by cu- er story, only one of the many stories that riosity and a desire to expand on funda- emerge when we view inorganic chem- mental science, we have come to appreci- istry from the perspective of a single ele- ate the vital role played by this relatively ment. precious element that forms the inorganic backbone of , the energy currency of atp, and the main component of bones and teeth. We have demonstrated the ability to

143 (4) Fall 2014 17 Phosphorus: endnotes From the Stars to Author’s Note: I am grateful for stimulating conversations with Professor Brandi M. Cossairt, Land & Sea Pro fessor Anna Frebel, Professor Jerrold Meinwald, and Dr. Willem Schipper. This material is based upon work supported by the National Science Foundation under che-1362118. 1 Norman Neill Greenwood and Alan Earnshaw, Chemistry of the Elements (Oxford: Butterworth- Heinemann, 1997). 2 D. C. B. Whittet and J. E. Chiar, “Cosmic Evolution of the Biogenic Elements and Compounds,” The Astronomy and Astrophysics Review 5 (1993), doi:10.1007/BF00872922. 3 B. Elvers and U. Fritz, Phosphorus Compounds, Inorganic to Plastics, Additives (Weinheim, Ger- many: Wiley-vch, 2011). 4 Kazunori Ozawa, ed., Lithium Rechargeable Batteries: Materials, Technology, and New Appli- cations (Weinheim, Germany: Wiley-vch, 2009). 5 Greenwood and Earnshaw, Chemistry of the Elements. 6 Paul C. J. Kamer and Piet W. N. M. van Leeuwen, Phosphorus (III) Ligands in Homogeneous Catal - ysis: Design and Synthesis (West Sussex; Chichester, U.K.: John Wiley & Sons, 2012). 7 Ibid. 8 R. Ayers, “The Life-Cycle of Chlorine, Part I: Chlorine Production and the Chlorine-Mercury Connection,” Journal of Industrial 1 (1997), doi:10.1162/jiec.1997.1.1.81. 9 Brandi M. Cossairt and Christopher C. Cummins, “Radical Synthesis of Trialkyl, Triaryl, Trisi- lyl and Tristannyl from P4,” New Journal of Chemistry 34 (2010), doi:10.1039/c0nj 00124d. 10 W. E. Dasent, Nonexistent Compounds: Compounds of Low Stability (New York: M. Dekker, 1965). 11 Keith B. Dillon, François Mathey, and John F. Nixon, Phosphorus: The Carbon Copy: From Organo- phosphorus to Phospha-organic Chemistry (New York: Wiley, 1998). 12 M. Ruck, D. Hoppe, B. Wahl, P. Simon, Y. Wang, and G. Seifert, “Fibrous Red Phosphorus,” An- gewandte Chemie International Edition 44 (2005), doi:10.1002/anie.200503017. 13 N. A. Piro, J. S. Figueroa, J. T. McKellar, and C. C. Cummins, “Triple-Bond Reactivity of Diphos - phorus Molecules,” Science 313 (2006), doi:10.1126/science.1129630. 14 G. Rathenau, “Optische und photochemische versuche mit ,” Physica 4 (1937): 503– 514, http://www.sciencedirect.com/science/article/B6X42-4F0H2V0-6T/2/62b38c13a477cb0 dc6b01d06d9a76727. 15 Daniel Tofan and Christopher C. Cummins, “Photochemical Incorporation of Diphosphorus Units into Organic Molecules,” Angewandte Chemie International Edition 49 (2010), doi:10.1002/ anie.201004385. 16 A. Rodionov, R. Kalendarev, J. Eiduss, and Yu. Zhukovskii, “Polymerization of Molecular (Yel- low) Arsenic,” Journal of Molecular Structure 380 (1996), doi:10.1016/0022-2860(95)09195-5. 17 Lee-Ping Wang, Daniel Tofan, Jiahao Chen, Troy Van Voorhis, and Christopher C. Cummins, “A Pathway to Diphosphorus from the Dissocation of Photoexcited Tetraphosphorus,” Royal Society of Chemistry Advances 3 (2013), doi:10.1039/c3ra43940b. 18 Brandi M. Cossairt, Mariam-Céline Diawara, and Christopher C. Cummins, “Facile Synthesis of AsP3,” Science 323 (2009), doi:10.1126/science.1168260. 19 Brandi M. Cossairt, Christopher C. Cummins, Ashley R. Head, Dennis L. Lichtenberger, Raphael J. F. Berger, Stuart A. Hayes, Norbert W. Mitzel, and Gang Wu, “On the Molecular and Electronic Structures of AsP3 and P4,” Journal of the American Chemical Society 132 (2010), doi:10.1021/ja102580d; and Adam M. Daly, Brandi M. Cossairt, Gavin Southwood, Spencer J. Carey, Christopher C. Cummins, and Stephen G. Kukolich, “Microwave Spectrum of Arsenic

18 Dædalus, the Journal ofthe American Academy of Arts & Sciences Tri ,” Journal of Molecular Spectroscopy 278 (2012): 68–71, http://www.sciencedirect Christopher .com/science/article/pii/S0022285212000410. C. Cummins 20 Jules Tshishimbi Muya, Erwin Lijnen, Minh Tho Nguyen, and Arnout Ceulemans, “Encapsula- tion of Small Base Molecules and Tetrahedral/Cubane-Like Clusters of Group V Atoms in the Boron Buckyball: A Functional Theory Study,” The Journal of Physical Chemistry A 115 (2011), doi:10.1021/jp107630q. 21 Eric Oelkers and Eugenia Valsami-Jones, “Phosphate Mineral Reactivity and Global Sustain - ability,” Elements 4 (2008): 83–87, http://elements.geoscienceworld.org/cgi/content/abstract/4/ 2/83. 22 White phosphorus is a commodity chemical that is also in demand for applications, in which setting it is valued for its incendiary effects (including the production of screens) and is known as “Willy Pete.” Small quantities of white phosphorus for research pur - poses were previously available from many chemical suppliers. After 2001, white phosphorus ceased to be available from catalog suppliers in the United States, but since red phosphorus was still available and can be converted to the white form by simple thermal depolymerization, this was not a major impediment to researchers. Now, both red and white phosphorus are Drug En - forcement Agency (dea) List 1 controlled chemicals, which has led to dif½culty in purchas- ing either form of the element. Why is phosphorus on this list? While there is no phosphorus whatsoever in the chemical composition of the much-abused drug , a pop - ular street method for synthesizing the drug involves a combination of phosphorus and hydro - gen iodide as a reducing agent for . For the same reason, elemental is also a dea List 1 chemical. My research group was fortunate to receive a gift of white phosphorus from Thermphos (see endnote 23); after arriving from the Netherlands, however, the shipment (which was around half a kilogram) was held up in customs in New Jersey until, with the assis- tance of mit’s general council and a customs broker properly licensed to receive shipments of List 1 chemicals, we were able to free the shipment. For more on the conversion of red to white phosphorus, see J. Brodkin, “Preparation of White Phosphorus from Red Phosphorus,” Journal of Chemical 37 (2) (1960), doi:10.1021/ ed037pA93.1. For more on the use of phosphorus in methamphetamine synthesis, see Harry F. Skinner, “Methamphetamine Synthesis via Hydriodic Acid/Red Phosphorus Reduction of Ephedrine,” Forensic Science International 48 (1990): 123–134, http://www.sciencedirect .com/science/article/pii/0379073890901047. 23 A company called Thermphos (recently gone out of business) in the Netherlands was situated adjacent to a nuclear power plant for the cheap electricity, and took its phosphate rock ship- ments from Florida, now mostly mined out. Thermphos was taking a leadership role toward the exciting goal of making phosphorus from waste and thereby realizing a vision of a sustainable phosphorus industry. White phosphorus is made in the United States as the ½rst step in the syn - thesis of glyphosate. See A. D. E. Grossbard, The Glyphosate (London; : Butter - worths, 1985). 24 John Emsley, The 13th Element: The Sordid Tale of Murder, , and Phosphorus (Malden, .: John Wiley & Sons, Inc., 2000). 25 Jan Willem Erisman, Mark A. Sutton, James Galloway, Zbigniew Klimont, and Wilfried Win - iwarter, “How a Century of Ammonia Synthesis Changed the World,” Nature Geoscience 1 (2008), doi:10.1038/ngeo325. 26 Anna Frebel, “Reconstructing the Cosmic Evolution of the Chemical Elements,” Dædalus 143 (4) (2014): 71–80; and Sean G. Ryan and Andrew J. Norton, Stellar Evolution and Nucleosyn thesis (Cambridge: Cambridge University Press, 2010). 27 Enrique Maciá, “The Role of Phosphorus in Chemical Evolution,” Chemical Society Reviews 34 (2005), doi:10.1039/B416855K. 28 Whittet and Chiar, “Cosmic Evolution of the Biogenic Elements and Compounds.”

143 (4) Fall 2014 19 Phosphorus: 29 Tina-Simone S. Neset and Dana Cordell, “Global Phosphorus Scarcity: Identifying Synergies From the for a Sustainable Future,” Journal of the Science of and Agriculture 92 (2012), doi:10.1002/ Stars to jsfa.4650. Land & Sea 30 P. Rutherford, M. Dudas, and R. Samek, “Environmental Impacts of Phosphogypsum,” Science of the Total Environment 149 (1994), doi:10.1016/0048-9697(94)90002-7; and C. Hull and W. Bur nett, “ of Florida Phosphogypsum,” Journal of Environmental Radioactivity 32 (3) (1996), doi:10.1016/0265-931X(95)00061-E. 31 Dana Cordell and Stuart White, “: Clarifying the Key Issues of a Vigorous De - bate about Long-term Phosphorus Security,” 3 (2011): 2027–2049, http://www .mdpi.com/2071-1050/3/10/2027. 32 Gabriel M. Filippelli, “The Global : Past, Present, and Future,” Elements 4 (2008): 89–95, http://elements.geoscienceworld.org/cgi/content/abstract/4/2/89. 33 S. A. Parsons and J. A. Smith, “Phosphorus Removal and Recovery from Municipal Waste- waters,” Elements 4 (2008): 109–112, http://elements.geoscienceworld.org/cgi/content/ abstract/4/2/109; and Kersti Linderholm, Anne-Marie Tillman, and Jan Erik Mattsson, “Life Cycle Assessment of Phosphorus Alternatives for Swedish Agriculture,” Resources, Conservation and Recycling 66 (2012): 27–39, http://www.sciencedirect.com/science/article/pii/S092134 4912001048. 34 Dana Cordell, Jan-Olof Drangert, and Stuart White, “The Story of Phosphorus: Global Food Security and Food for Thought,” Global Environmental Change 19 (2009): 292–305, http:// www.sciencedirect.com/science/article/pii/S095937800800099X. 35 S. P. Golovan, R. G. Meidinger, A. Ajakaiye, M. Cottrill, M. Z. Wiederkehr, D. J. Barney, C. Plante, J. W. Pollard, M. Z. Fan, M. A. Hayes, J. Laursen, J. P. Hjorth, R. R. Hacker, J. P. Phillips, and C. W. Forsberg, “Pigs Expressing Salivary Phytase Produce Low-Phosphorus Manure,” Na ture Biotechnology 19 (2001), doi:10.1038/90788.

20 Dædalus, the Journal ofthe American Academy of Arts & Sciences