Red phosphorus

Red phosphorus is an amorphous form of phosphorus. Crystalline forms of red phosphorus include Hittorf's phosphorus and fibrous red phosphorus. The structure of red phosphorus contains the fragments illustrated below:{{Cite journal |last1=Zhou |first1=Yuxing |last2=Elliott |first2=Stephen R. |last3=Deringer |first3=Volker L. |date=2023-06-12 |title=Structure and Bonding in Amorphous Red Phosphorus** |journal=Angewandte Chemie International Edition |language=en |volume=62 |issue=24 |pages=e202216658 |doi=10.1002/anie.202216658 |issn=1433-7851 |pmc=10952455 |pmid=36916828}}

File:Red phosphorus structure 1.pngFile:Red phosphorus structure 2.png

One method of preparing red phosphorus involves heating white phosphorus in an inert atmosphere like nitrogen or carbon dioxide, with iodine as catalyst.{{Cite web |title=Red Phosphorus - Structure, Properties, Preparation and Applications |url=https://www.vedantu.com/chemistry/red-phosphorus |access-date=2024-08-12 |website=VEDANTU |language=en}}

Another theoretically possible method of red phosphorus production is via light irradiation of white phosphorus.{{Cite web |title=White phosphorus |url=https://www.acs.org/molecule-of-the-week/archive/w/white-phosphorus.html |access-date=2024-08-12 |website=American Chemical Society |language=en}} However, it has not been used industrially, likely due to the suspicious quality and unidentified structure the product.{{Cite AV media |url=https://www.youtube.com/watch?v=radd2pI2O0w |title=Turning White Phosphorus into Red using Sunlight |date=2018-07-25 |last=Extractions&Ire |access-date=2024-08-12 |via=YouTube}}{{Better source needed|reason=Citation is based on YouTube video, which may not demonstrate professional experimental techniques and results may be unreliable|date=August 2024}}

Under standard conditions, red phosphorus is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is −17.6 kJ/mol.{{Housecroft2nd|page=392}} Red phosphorus is kinetically most stable.

Being polymeric, red phosphorus is insoluble in solvents. It shows semiconductor properties.

Due to such a kinetic stability, red phosphorus doesn't spontaneously ignite in air. It doesn't disproportionate in the presence of alkali, and is less reactive towards halogens, sulfur, and metals compared with white phosphorus.

Red phosphorus can be used as a flame retardant in resins. Its mechanism of action involves the formation of polyphosphoric acid (the hydrogen atoms are from the resin) and char, which prevents flame propagation.{{Cite web |title=Features of red phosphorus fire retardants {{!}} Product descriptions｜RIN KAGAKU KOGYO |url=https://www.rinka.co.jp/english/products/flame-retardant/advantage.html |access-date=2024-08-15 |website=www.rinka.co.jp}}

However, for electronic/electrical systems, red phosphorus flame retardant has been effectively banned by major OEMs due to its tendency to induce premature failures.{{cite web |url=http://resources.dfrsolutions.com/Webcasts/2015/Red-Phosphorus-Reliability-Alert.pdf |title=Red Phosphorus Reliability Alert |access-date=2018-01-01 |archive-url=https://web.archive.org/web/20180102013053/http://resources.dfrsolutions.com/Webcasts/2015/Red-Phosphorus-Reliability-Alert.pdf |archive-date=2018-01-02 |url-status=dead }} One persistent problem is that red phosphorus in epoxy molding compounds induces elevated leakage current in semiconductor devices.Craig Hillman, Red Phosphorus Induced Failures in Encapsulated Circuits, https://www.dfrsolutions.com/hubfs/Resources/services/Red-Phosphorus-Induced-Failures-in-Encapsulated-Circuits.pdf?t=1513022462214 Another problem was acceleration of hydrolysis reactions in PBT insulating material.Dock Brown, The Return of the Red Retardant, SMTAI 2015, https://www.dfrsolutions.com/hubfs/Resources/services/The-Return-of-the-Red-Retardant.pdf?t=1513022462214

Red phosphorus is used, along with abrasives, on the strike pads of modern safety matches. The match head, containing potassium chlorate, will ignite upon friction with the strike pad.{{cite web |title=Fire |url=http://mysite.du.edu/~jcalvert/phys/phosphor.htm#Fire |url-status=live |archive-url=https://web.archive.org/web/20111104054408/http://mysite.du.edu/~jcalvert/phys/phosphor.htm#Fire |archive-date=4 November 2011 |access-date=19 November 2011}} However, the red color of the matchhead is due to addition of red dyes, and has nothing to do with red phosphorus content.{{Cite web |date=2020-05-27 |title=How Do Safety Matches Work? |url=https://www.reagent.co.uk/blog/how-do-safety-matches-work/ |access-date=2024-08-12 |language=en-GB}}

Red phosphorus reacts with bromine and iodine to form phosphorus tribromideJ. F. Gay, R. N. Maxson "Phosphorus(III) Bromide" Inorganic Syntheses, 1947, vol. 2, 147ff. {{doi|10.1002/9780470132333.ch43}}{{cite journal |author1=Burton, T. M. |author2=Degerping, E. F. |year=1940 |title=The Preparation of Acetyl Bromide |journal=Journal of the American Chemical Society |volume=62 |issue=1 |pages=227 |doi=10.1021/ja01858a502}} and phosphorus triiodide. Both are useful as halogenation agents, like replacing the hydroxyl group of alcohols. Phosphorus triiodide can also be used to produce hydroiodic acid after hydrolysis. This reaction is notable in the illicit production of methamphetamine and Krokodil, where hydrogen iodide acts as a reducing agent.{{cite journal |last1=Skinner |first1=Harry F. |year=1990 |title=Methamphetamine synthesis via hydriodic acid/Red phosphorus reduction of ephedrine |journal=Forensic Science International |volume=48 |issue=2 |pages=123–134 |doi=10.1016/0379-0738(90)90104-7}}

Red phosphorus is often used to prepare chemicals where the P-P bond is retained. Upon room temperature action with sodium chlorite, Na₂H₂P₂O₆ is formed.Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition, 2013, D.E.C. Corbridge, CRC Pres, Taylor Francis Group, {{ISBN|978-1-4398-4088-7}}

Red phosphorus can be used as an elemental photocatalyst for hydrogen formation from the water.Applied Catalysis B: Environmental, 2012, 111–112, 409–414. It has also been researched as a sodium ion battery anode.{{Cite journal |last1=Liu |first1=Yihang |last2=Liu |first2=Qingzhou |last3=Jian |first3=Cheng |last4=Cui |first4=Dingzhou |last5=Chen |first5=Mingrui |last6=Li |first6=Zhen |last7=Li |first7=Teng |last8=Nilges |first8=Tom |last9=He |first9=Kai |last10=Jia |first10=Zheng |last11=Zhou |first11=Chongwu |date=2020-05-20 |title=Red-phosphorus-impregnated carbon nanofibers for sodium-ion batteries and liquefaction of red phosphorus |journal=Nature Communications |language=en |volume=11 |issue=1 |pages=2520 |doi=10.1038/s41467-020-16077-z |issn=2041-1723 |pmc=7239945 |pmid=32433557|bibcode=2020NatCo..11.2520L}}

{{main|Allotropes of phosphorus#Violet or Hittorf's phosphorus}}Hittorf's phosphorus, or violet phosphorus, is one of the crystalline forms of red phosphorus.{{Cite journal |last1=Liu |first1=Cheng |last2=Wang |first2=Yinghao |last3=Sun |first3=Jie |last4=Chen |first4=Aibing |date=April 2020 |title=A Review on Applications of Layered Phosphorus in Energy Storage |journal=Transactions of Tianjin University |language=en |volume=26 |issue=2 |pages=104–126 |doi=10.1007/s12209-019-00230-x |bibcode=2020TrTU...26..104L |issn=1006-4982|doi-access=free }}{{Cite book |last=Housecroft |first=Catherine E.|title=Inorganic chemistry |date=2018 |publisher=Pearson |isbn=978-1-292-13414-7 |edition=Fifth |location=Harlow, England ; New York |pages=511}} It adopts the following structure:File:Violetter Phosphor.svg

File:Hittorf's violet phosphorus.pngViolet phosphorus can be prepared by sublimation of red phosphorus in a vacuum, in the presence of an iodine catalyst.

It is chemically similar to red phosphorus. There are, however, subtle differences. Violet phosphorus ignites upon impact in air, while red phosphorus is impact stable. Violet phosphorus doesn't ignite in the presence of air upon room temperature contact with bromine, unlike red phosphorus.{{citation needed|date=December 2024}} The reaction of red phosphorus and bromine alone does not generate a flame.{{citation needed|date=December 2024}}

Fibrous red phosphorus is another crystalline form of red phosphorus. It is obtained along with violet phosphorus when red phosphorus is sublimed in vacuum in the presence of iodine.{{Cite journal |last1=Athira |first1=T. K. |last2=Roshith |first2=M. |last3=Satheesh Babu |first3=T. G. |last4=Ravi Kumar |first4=Darbha V. |date=2021-01-15 |title=Fibrous red phosphorus as a non-metallic photocatalyst for the effective reduction of Cr(VI) under direct sunlight |url=https://www.sciencedirect.com/science/article/pii/S0167577X20314579 |journal=Materials Letters |volume=283 |pages=128750 |doi=10.1016/j.matlet.2020.128750 |bibcode=2021MatL..28328750A |issn=0167-577X}}

It is structurally similar to violet phosphorus. However, in fibrous red phosphorus, phosphorus chains lie parallel instead of orthogonal, unlike violet phosphorus. Such a structure is depicted below:{{Cite journal |last1=Ruck |first1=Michael |last2=Hoppe |first2=Diana |last3=Wahl |first3=Bernhard |last4=Simon |first4=Paul |last5=Wang |first5=Yuekui |last6=Seifert |first6=Gotthard |date=2005-11-25 |title=Fibrous Red Phosphorus |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.200503017 |journal=Angewandte Chemie International Edition |language=en |volume=44 |issue=46 |pages=7616–7619 |doi=10.1002/anie.200503017 |pmid=16245382 |issn=1433-7851}}

File:Red_phosphorus.pngFibrous red phosphorus, similar to red phosphorus, displays activity as a photocatalyst.{{Cite journal |last1=Hu |first1=Zhuofeng |last2=Guo |first2=Weiqing |date=May 2021 |title=Fibrous Phase Red Phosphorene as a New Photocatalyst for Carbon Dioxide Reduction and Hydrogen Evolution |url=https://onlinelibrary.wiley.com/doi/10.1002/smll.202008004 |journal=Small |language=en |volume=17 |issue=19 |pages=e2008004 |doi=10.1002/smll.202008004 |pmid=33792191 |issn=1613-6810}}

• White phosphorus
• Violet phosphorus
• Allotropes of phosphorus
• Phosphorus

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Category:Allotropes

Category:Phosphorus