[WP = white phosphorus ; RP = red phosphorus ; ARP = activated red phosphorus]
Tom from Extraction & Ire did a video two years ago(2018) on converting WP to RP by keeping the former in sunlight for several days. He chose chloroform solvent to dissolve WP in a glass vial. The solution started to go deep orange to red on slight heating and then keeping in sunlight for 5 days. After 5 days, he tested the solution with sodium hydroxide solution to confirm that it is RP (RP doesn't react with $\ce{NaOH}$, WP does). On dumping it to the $\ce{NaOH}$ solution, it immediately started reacting (phosphine was evolving which had a dreadful smell). After 15 minutes on adding, the orange-red color vanished, that means all of the phosphorus has reacted. Some white crystals formed in the solution which is presumed to be sodium formate ($\ce{HCOONa}$) due to the chloroform (isn't it soluble in water?).
$$\ce{P4_{(?)} + 3NaOH + 3H2O -> PH3 ^ + 3NaH2PO2}$$
$$\ce{2NaH2PO2 -> PH3 ^ + Na2HPO4}$$
$$\ce{CHCl3 + 4NaOH -> HCOONa (\downarrow ?) + 3NaCl + 2H2O}$$
So, the conversion failed. He apparently named the species "ARP". He made the following conclusion:
\begin{array}{c|c|c|c} \mathbf{~} & \mathbf{WP} & \mathbf{RP} & \mathbf{ARP} \\\hline \text{color} & \text{white} & \text{red} & \text{red}\\ \text{soluble in CHCl3} & \text{Yes} & \text{No} & \text{No}\\ \text{Reactive towards NaOH} & \text{Yes} & \text{No} & \text{Yes}\end{array}
So, apparently WP converted to an unknown species(allotrope?) which he assumed to be ARP. He doesn't know its composition nor did he find convincing literature. Google didn't give any relevant hits except two papers. First one says it is polymerized organophosphorus chains and the second one says it is series of polyphosphides*.
Questions:
- What is the actual composition of ARP?
- Is it an allotrope? If so, other allotropes were discovered centuries ago, why was it unknown until recently? What made it so long to be discovered?
References
- Sukhov, Boris & Malysheva, S. & Kuimov, Vladimir & Smetannikov, Yu & Tarasova, N. & Lupanov, A. & Gusarova, N. & Trofimov, BA. (2004). Reaction of Activated Red Phosphorus with Allyl Bromide under Phase-Transfer Catalysis. Russian Journal of General Chemistry - RUSS J GEN CHEM. 74. 1128-1129. 10.1023/B:RUGC.0000045878.42411.31.
- Nucleophilic Activation of Red Phosphorus for Controlled Synthesis of Polyphosphides, Minyoung Jo, Alina Dragulescu-Andrasi, L. Zane Miller, Chongin Pak, and Michael Shatruk,Inorganic Chemistry 2020 59 (8), 5483-5489 DOI: 10.1021/acs.inorgchem.0c00108
The 2020 paper says "RP is readily activated by refluxing it with different potassium alkoxide to give soluble polyphosphide ions". Now, polyphosphides is known and has been studied a lot (first paper I could find dates way back in 1967). So, what does "readily activation of red phosphorus" mean in this context? Could it mean ARP?