This work was supported by the National Nature Science Foundation of China (21301104), the Fundamental Research Funds for the Central Universities (FRF-TP-16-019A3), and the State Key Laboratory of Chemical Engineering (SKL-ChE-14A04).

1. Synthesis of Mono-(2,3-dimethylbutyl)phosphinic acid 18,19
<ol>
	<li>Reaction
	<ol>
		<li>Weigh 31.80 g sodium hypophosphite hydrate, 16.00 g acetic acid, 8.42 g 2,3-dimethyl-1-butene, 0.73 g di-tert-butylnperoxide (DTBP), and 25.00 g tetrahydrofuran (THF) into a 100 mL Teflon-lined stainless steel autoclave, put a magnetic stirrer into the autoclave, and seal it.</li>
		<li>Put the autoclave in a vertical tube furnace under which i...

<ol>
	<li>Swain, B., Otu, E. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Competitive+extraction+of+lanthanides+by+solvent+extraction+using+Cyanex+272:+Analysis,+classification+and+mechanism.">Competitive extraction of lanthanides by solvent extraction using Cyanex 272: Analysis, classification and mechanism.</a> Sep Purif Technol. 83, 82-90 (2011).</li><li>Wang, Y. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+novel+extraction+process+based+on+CYANEX+(R)+572+for+separating+heavy+rare+earths+from+ion-adsorbed+deposit.">The novel extraction process based on CYANEX (R) 572 for separating heavy rare earths from ion-adsorbed deposit.</a> Sep Purif Technol. 151, 303-308 (2015).</li><li>Regel-Rosocka, M., Staszak, K., Wieszczycka, K., Masalska, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Removal+of+cobalt(II)+and+zinc(II)+from+sulphate+solutions+by+means+of+extraction+with+sodium+bis(2,4,4-trimethylpentyl)phosphinate+(Na-Cyanex+272).">Removal of cobalt(II) and zinc(II) from sulphate solutions by means of extraction with sodium bis(2,4,4-trimethylpentyl)phosphinate (Na-Cyanex 272).</a> Clean Technol Envir. 18 (6), 1961-1970 (2016).</li><li>Hereijgers, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Co(II)/Ni(II)+with+Cyanex+272+using+a+flat+membrane+microcontactor:+Stripping+kinetics+study,+upscaling+and+continuous+operation.">Separation of Co(II)/Ni(II) with Cyanex 272 using a flat membrane microcontactor: Stripping kinetics study, upscaling and continuous operation.</a> Chem Eng Res Des. 111, 305-315 (2016).</li><li>Lee, M. S., Banda, R., Min, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Hf(IV)-Zr(IV)+in+H2SO4+solutions+using+solvent+extraction+with+D2EHPA+or+Cyanex+272+at+different+reagent+and+metal+ion+concentrations.">Separation of Hf(IV)-Zr(IV) in H2SO4 solutions using solvent extraction with D2EHPA or Cyanex 272 at different reagent and metal ion concentrations.</a> Hydrometallurgy. 152, 84-90 (2015).</li><li>Noori, M., Rashchi, F., Babakhani, A., Vahidi, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+recovery+and+separation+of+nickel+and+vanadium+in+sulfate+media+using+mixtures+of+D2EHPA+and+Cyanex+272.">Selective recovery and separation of nickel and vanadium in sulfate media using mixtures of D2EHPA and Cyanex 272.</a> Sep Purif Technol. 136, 265-273 (2014).</li><li>Li, X. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermodynamics+and+mechanism+of+vanadium(IV)+extraction+from+sulphate+medium+with+D2EHPA,+EHEHPA+and+CYANEX+272+in+kerosene.">Thermodynamics and mechanism of vanadium(IV) extraction from sulphate medium with D2EHPA, EHEHPA and CYANEX 272 in kerosene.</a> Trans Nonferrous Met Soc China. 22 (2), 461-466 (2012).</li><li>Das, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+the+nature+of+organophosphorous+acid+moiety+on+co-extraction+of+U(VI)+and+mineral+acid+from+aqueous+solutions+using+D2EHPA,+PC88A+and+Cyanex+272.">Effect of the nature of organophosphorous acid moiety on co-extraction of U(VI) and mineral acid from aqueous solutions using D2EHPA, PC88A and Cyanex 272.</a> Hydrometallurgy. 152, 129-138 (2015).</li><li>Baba, A. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+copper+from+leach+liquor+of+metallic+component+in+discarded+cell+phone+by+Cyanex+(R)+272.">Extraction of copper from leach liquor of metallic component in discarded cell phone by Cyanex (R) 272.</a> JESTEC. 11 (6), 861-871 (2016).</li><li>Du, R. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave-assisted+synthesis+of+dialkylphosphinic+acids+and+a+structure-reactivity+study+in+rare+earth+metal+extraction.">Microwave-assisted synthesis of dialkylphosphinic acids and a structure-reactivity study in rare earth metal extraction.</a> RSC Adv. 5 (126), 104258-104262 (2015).</li><li>Du, R. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=alpha,+beta-Substituent+effect+of+dialkylphosphinic+acids+on+anthanide+extraction.">alpha, beta-Substituent effect of dialkylphosphinic acids on anthanide extraction.</a> RSC Adv. 6 (61), 56004-56008 (2016).</li><li>Wang, J. L., Xu, S. X., Li, L. Y., Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+organic+phosphinic+acids+and+studies+on+the+relationship+between+their+structure+and+extraction-separation+performance+of+heavy+rare+earths+from+HNO3+solutions.">Synthesis of organic phosphinic acids and studies on the relationship between their structure and extraction-separation performance of heavy rare earths from HNO3 solutions.</a> Hydrometallurgy. 137, 108-114 (2013).</li><li>Hino, A., Nishihama, S., Hirai, T., Komasawa, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Practical+study+of+liquid-liquid+extraction+process+for+separation+of+rare+earth+elements+with+bis+(2-ethylhexyl)+phosphinic+acid.">Practical study of liquid-liquid extraction process for separation of rare earth elements with bis (2-ethylhexyl) phosphinic acid.</a> J Chem Eng Jpn. 30 (6), 1040-1046 (1997).</li><li>Ju, Z. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+extraction+performance+of+di-decylphosphinic+acid.">Synthesis and extraction performance of di-decylphosphinic acid.</a> Chin J Nonferrous Met. 20 (11), 2254-2259 (2010).</li><li>Li, L. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dialkyl+phosphinic+acids:+Synthesis+and+applications+as+extractant+for+nickel+and+cobalt+separation.">Dialkyl phosphinic acids: Synthesis and applications as extractant for nickel and cobalt separation.</a> Trans Nonferrous Met Soc China. 20, 205-210 (2010).</li><li>Wang, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvent+extraction+of+rare+earth+ions+from+nitrate+media+with+new+extractant+di-(2,3-dimethylbutyl)-phosphinic+acid.">Solvent extraction of rare earth ions from nitrate media with new extractant di-(2,3-dimethylbutyl)-phosphinic acid.</a> J Rare Earths. 34 (7), 724-730 (2016).</li><li>Hu, W. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+properties+of+di-tertiary+alkylphosphinic+acids.">Synthesis and properties of di-tertiary alkylphosphinic acids.</a> Chem J Chin Univ-Chin. 15 (6), 849-853 (1994).</li><li>Wang, J. L., Chen, G., Xu, S. M., Li, L. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+novel+nonsymmetric+dialkylphosphinic+acid+extractants+and+studies+on+their+extraction-separation+performance+for+heavy+rare+earths.">Synthesis of novel nonsymmetric dialkylphosphinic acid extractants and studies on their extraction-separation performance for heavy rare earths.</a> Hydrometallurgy. 154, 129-136 (2015).</li><li>Wang, J. L., Xie, M. Y., Wang, H. J., Xu, S. 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P., Almela, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+the+degradation+compounds+formed+by+the+oxidation+of+thiophosphinic+acids+and+phosphine+sulfides+with+nitric+acid.">Determination of the degradation compounds formed by the oxidation of thiophosphinic acids and phosphine sulfides with nitric acid.</a> Anal Sci. 18 (7), 799-804 (2002).</li><li>Darvishi, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synergistic+effect+of+Cyanex+272+and+Cyanex+302+on+separation+of+cobalt+and+nickel+by+D2EHPA.">Synergistic effect of Cyanex 272 and Cyanex 302 on separation of cobalt and nickel by D2EHPA.</a> Hydrometallurgy. 77, 227-238 (2005).</li></ol>

The authors have nothing to disclose.

The most critical step within the protocol is the mono-alkylphosphinic acid synthesis (Figure 1a). In this reaction, a higher yield and less dialkylphosphinic acid by-product is better. Increasing the molar ratio of NaH2PO2/olefin A will improve the yield and inhibit the generation of dialkylphosphinic acid by-product. However, a large NaH2PO2 dosage will also increase the cost and cause a stirring problem. The preferred molar rati...

Acidic organophosphorus extractants are widely used in the traditional hydrometallurgy field for extraction and separation of rare earth ions1,2, non-ferrous metals (like Co/Ni3,4), rare metals (such as Hf/Zr5, V6,7), actinides8, etc. In recent years, they have also attracted more attention in the fields of secondary resource recycling and high-level liquid waste disposal9. Di-(2-ethylhexyl)phosphoric acid (D2EHPA or P204), 2-ethylhexylphosphoric acid mono-2-ethylhexyl ester (EHEHPA, PC 88A, or P507), and Di-(2,4,4&#39;-trimethylpentyl)-phosphinic acid (Cyanex272), which are representatives of dialkylphosphoric acids, alkylphosphoric acid mono-alkyl esters, and dialkylphosphinic acids respectively, are the most commonly used extractants. Their acidity decreases in the following sequence: P204 &#62; P507 &#62; Cyanex 272. The corresponding extraction ability, extraction capacity, and stripping acidity are all in the order of P204 &#62; P507 &#62; Cyanex 272, and the separation performance is in the opposite order. These three extractants are effective in most cases. However, there are still some conditions where they are not so efficient: in heavy rare earths separation, of which the existing main problems are the poor selectivity and high stripping acidity for P204 and P507, low extraction capacity, and emulsion tendency during extraction for Cyanex 272. Thus, the development of novel extractants has drawn greater attention in recent years.
The class of dialkylphosphinic acid extractants is considered to be one of the most important research aspects to develop new extractants. Recent research showed that the extraction ability of dialkylphosphinic acids depends largely on the structure of the alkyl substituent10,11. It can be a wide range from significantly higher than that of P507 to lower than that of Cyanex 27212. However, the exploration of novel dialkylphosphinic acid extractants is restricted to the commercial olefin structure10,12,13,14,15,16. Though dialkylphosphinic acid extractants can also be synthesized by the Grignard-reaction method, the reaction conditions are rigorous12,17.
NSDAPA, of which the two alkyls are different, opens a door to the exploration of new extractants. It makes the structures of dialkylphosphinic acid more diverse, and its extraction and separation performance can be fine-tuned by modifying both of its alkyl structures. The traditional synthetic method of NSDAPA used PH3 as a phosphorus source, which has many drawbacks like high toxicity, rigorous reaction conditions, and difficult purification. Recently we reported a new method to synthesize NSDAPA using sodium hypophosphite as a phosphorus source (see Figure 1) and successfully synthesized three NSDAPAs18. This detailed protocol can help new practitioners repeat the experiments and master the synthetic method of NSDAPA extractants. We take (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid as an example. The names and structures of olefin A, the mono-alkylphosphinic acid intermediate, olefin B, and the corresponding NSDAPA are shown in Table 1.

<table style="border-collapse:collapse;width:687pt" width="916">
	<colgroup>
		<col style="width:185pt" width="247" />
		<col style="width:290pt" width="387" />
		<col style="width:93pt" width="124" />
		<col style="width:119pt" width="158" />
	</colgroup>
	<tbody>
		<tr height="102" style="height:76.5pt">
			<td class="xl17" height="102" style="width:185pt;height:76.5pt" width="247">sodium hypophosphite hydrate</td>
			<td class="xl17" style="width:290pt" width="387">Tianjin Fuchen Chemical Reagents Factory</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: NaH2PO2&#8729;H2O, purity &#8805;99.0%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">2,3-dimethyl-1-butene</td>
			<td class="xl17" style="width:290pt" width="387">Adamas Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C6H12, purity &#8805;99%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">diisobutylene</td>
			<td class="xl17" style="width:290pt" width="387">Shanghai&#160;Aladdin&#160;Bio-Chem&#160;Technology&#160;Co.,&#160;LTD</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C8H16, purity 97%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">acetic acid</td>
			<td class="xl17" style="width:290pt" width="387">Sinopharm Chemical Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C2H4O2, purity &#8805;99.5%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">di-tert-butylnperoxide</td>
			<td class="xl17" style="width:290pt" width="387">Sinopharm Chemical Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C8H18O2, purity &#8805;97.0%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">tetrahydrofuran</td>
			<td class="xl17" style="width:290pt" width="387">Beijing Chemical Works</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C4H8O, purity A.R.</td>
		</tr>
		<tr height="102" style="height:76.5pt">
			<td class="xl17" height="102" style="width:185pt;height:76.5pt" width="247">amantadine hydrochloride</td>
			<td class="xl17" style="width:290pt" width="387">Shanghai&#160;Aladdin&#160;Bio-Chem&#160;Technology&#160;Co.,&#160;LTD</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C10H17N&#8729;HCl, purity 99%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">ethyl ether</td>
			<td class="xl17" style="width:290pt" width="387">Sinopharm Chemical Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C4H10O, purity &#8805;99.7%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">ethyl acetate</td>
			<td class="xl17" style="width:290pt" width="387">Xilong Chemical Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C4H8O2, purity &#8805;99.5%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">acetone</td>
			<td class="xl17" style="width:290pt" width="387">Beijing Chemical Works</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: C3H6O, purity &#8805;99.5%</td>
		</tr>
		<tr height="75" style="height:56.25pt">
			<td class="xl17" height="75" style="width:185pt;height:56.25pt" width="247">sodium hydroxide</td>
			<td class="xl17" style="width:290pt" width="387">Xilong Chemical Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: NaOH, purity &#8805;96.0%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">concentrated sulfuric acid</td>
			<td class="xl17" style="width:290pt" width="387">Sinopharm Chemical Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: H2SO4, purity 95-98%</td>
		</tr>
		<tr height="75" style="height:56.25pt">
			<td class="xl17" height="75" style="width:185pt;height:56.25pt" width="247">hydrochloric acid</td>
			<td class="xl17" style="width:290pt" width="387">Beijing Chemical Works</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: HCl, purity 36-38%</td>
		</tr>
		<tr height="75" style="height:56.25pt">
			<td class="xl17" height="75" style="width:185pt;height:56.25pt" width="247">sodium chloride</td>
			<td class="xl17" style="width:290pt" width="387">Sinopharm Chemical Reagent Co., Ltd.</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: NaCl, purity &#8805;99.5%</td>
		</tr>
		<tr height="77" style="height:57.75pt">
			<td class="xl17" height="77" style="width:185pt;height:57.75pt" width="247">anhydrous magnesium sulfate</td>
			<td class="xl17" style="width:290pt" width="387">Tianjin Jinke Institute of Fine Chemical Industry</td>
			<td class="xl17" style="width:93pt" width="124"></td>
			<td class="xl17" style="width:119pt" width="158">Molecular formula: MgSO4, purity &#8805;99.0%</td>
		</tr>
		<tr height="103" style="height:77.25pt">
			<td class="xl19" height="103" style="width:185pt;height:77.25pt" width="247">Cobalt(II) chloride hexahydrate</td>
			<td class="xl19" style="width:290pt" width="387">Xilong Chemical Co., Ltd.</td>
			<td class="xl19" style="width:93pt" width="124"></td>
			<td class="xl19" style="width:119pt" width="158">Molecular formula: CoCl2&#8729;6H2O, purity &#8805;99.0%</td>
		</tr>
	</tbody>
</table>

synthesis of high purity nonsymmetric dialkylphosphinic acid extractants

We present the synthesis of (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid as an example to demonstrate a method for the synthesis of high purity nonsymmetric dialkylphosphinic acid extractants. Low toxic sodium hypophosphite was chosen as the phosphorus source to react with olefin A (2,3-dimethyl-1-butene) to generate a monoalkylphosphinic acid intermediate. Amantadine was adopted to remove the dialkylphosphinic acid byproduct, as only the monoalkylphosphinic acid can react with amantadine to form an amantadine&#8729;mono-alkylphosphinic acid salt, while the dialkylphosphinic acid cannot react with amantadine due to its large steric hindrance. The purified monoalkylphosphinic acid was then reacted with olefin B (diisobutylene) to yield nonsymmetric dialkylphosphinic acid (NSDAPA). The unreacted monoalkylphosphinic acid can be easily removed by a simple base-acid post-treatment and other organic impurities can be separated out through the precipitation of the cobalt salt. The structure of the (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid was confirmed by 31P NMR, 1H NMR, ESI-MS, and FT-IR. The purity was determined by a potentiometric titration method, and the results indicate that the purity can exceed 96%.

31P NMR spectra were collected for the mono-(2,3-dimethylbutyl)phosphinic acid before and after purification by the amantadine method (Figure 1a-b). 31P NMR spectra, 1H NMR spectra, MS spectra, and FT-IR spectra were collected for (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid (see Figure 3, Figure 4, Figure 5</str...

Watch this Scientific Journal Video about Synthesis of High Purity Nonsymmetric Dialkylphosphinic Acid Extractants at JoVE.com

Synthesis of High Purity Nonsymmetric Dialkylphosphinic Acid Extractants

A protocol for the synthesis of high purity nonsymmetric dialkylphosphinic acid extractants is presented, taking (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid as an example.

We present the synthesis of (2,3-dimethylbutyl)(2,4,4&#39;-trimethylpentyl)phosphinic acid as an example to demonstrate a method for the synthesis of high ...

The overall goal of this protocol, is to introduce a universal synthetic method for nonsymmetric dialkylphosphinic acid extractants to a free radical addition reaction using sodium hypophosphite as a phosphorus source. The method can for a potential in the hydrometallurgy to develop a new dialkylphosphinic acid extractants. And novel potential extraction and separation with class of extractants.Compared to the traditional method, which use phosphate as a phosphorus source, this method had the advantages of low toxicity, reaction conditions, easy purification, and potential for larger-scale production. The video takes two, three-dimethylbutyl-two, four, four-trimethylpentylphosphinic acid as an example, to demonstrate the synthesis of high-purity NSDAPA extractants. First, sodium hypophosphite reacted with two-three dimethyl-one-butene, mono-DMBPA.Amantadine was adopted to remove the byproduct di-DMBPA, since only the mono-DMBPA can react with amantadine to form an amantadine mono-DMBPA salt, while the di-DMBPA cannot due to its large steric hindrance. The purified mono-DMBPA was then reacted with di-isobutylene to yield two, three-dimethylbutyl-two, four, four-trimethylpentylphosphinic acid. The unreacted mono-DMBPA can be easily removed by a simple base-acid post treatment, and other organic impurities can be separated out through the precipitation of the cobalt salt.First, weigh the appropriate reagents into a 100 milliliter teflon-lined stainless steel autoclave. Place a magnetic stirrer into the autoclave and seal it. Place the autoclave in a vertical tube furnace placed on a magnetic stirring apparatus.Start the magnetic stirring apparatus, and set the speed to 800 RPM. Then, start the heating program of the temperature controller connected to the autoclave. After the reaction is complete, transfer the mixture containing the product to a 250 milliliter one neck round bottom flask.Remove the solvent and unreacted oliphants using a rotary evaporator. Following this, transfer the residues to a 250 milliliter separating funnel. Add 50 milliliters of four percent sodium hydroxide solution to the separating funnel, and shake vigorously.After the phases have separated, transfer the bottom aqueous phase into a 500 milliliter separating funnel. Wash the organic phase three times with 20 milliliters of four percent sodium hydroxide solution to ensure that the aqueous phase exceeds pH 10. Then transfer the aqueous phases into the 500 milliliter separating funnel containing the first aqueous phase.Add 90 milliliters of 10%sulfuric acid solution and 50 milliliters of ethyl ether to the separating funnel containing the combined aqueous phases, and shake vigorously. After the phases have separated, transfer the top organic phase into another 500 milliliter separating funnel. Extract the aqueous phase three times with 30 milliliters of ethyl ether.Then transfer the organic phase into the 500 milliliter separating funnel containing the first organic phase. Wash the combined ethyl ether solution four times with 100 milliliters of saturated sodium chloride solution. After transferring the ethyl ether solution to a round bottom flask, add four grams of anhydrous magnesium sulfate to remove any soluble water.Filter it to remove the solid, and collect the liquid in a clean 250 milliliter one neck round bottom flask. Then remove the ethyl ether using the rotary evaporator to obtain the crude product. Add the crude product dropwise to a previously prepared amantadine solution.After allowing the solution to sit overnight, filter it under reduced pressure. Then wash the filter cake with 200 milliliters of ethyl ether. Transfer the filter cake to a 500 milliliter beaker.Add 80 milliliters of one molar hydrochloric acid, and stir the mixture for five minutes. Then add 70 milliliters of ethyl acetate, and stir the mixture for another five minutes. Now add the mixture to a 250 milliliter separating funnel, and transfer the bottom aqueous phase into a 250 milliliter separating funnel.After extracting the aqueous phase with ethyl acetate, wash the ethyl acetate solution twice with 30 milliliters of one molar hydrochloric acid and three times with 80 milliliters of saturated sodium chloride. After transferring the ethyl acetate solution to a round bottom flask, add four grams of anhydrous magnesium sulfate to remove any soluble water. Filter to remove the solid, and collect the liquid in a clean 250 milliliter one neck round bottom flask.Then remove the ethyl acetate using a rotary evaporator to obtain the pure product. Transfer the purified product to a 100 milliliter teflon-lined stainless steel autoclave. Add the appropriate reagents and a magnetic stirrer to the autoclave, and seal it.Place the autoclave in a vertical tube furnace placed on a magnetic stirring apparatus. Start the magnetic stirring apparatus and set the speed to 800 RPM. Start the heating program of the temperature controller connected to the autoclave.When the reaction system cools down to room temperature, add another 0.3 grams of DTBP to the autoclave and restart the heating program. After the reaction is complete, dilute the product with 100 milliliters of ethyl ether, and transfer the solution to a 250 milliliter separating funnel. Wash the ethyl ether solution three times with 30 milliliters of four percent sodium hydroxide solution to ensure that the aqueous phase exceeds pH 10.After removing the bottom aqueous phase, add 70 milliliters of 10%sulfuric acid solution to acidify the product. Wash the acidified ethyl ether solution several times with 80 milliliters of saturated sodium chloride solution until the aqueous phase pH is six to seven. After transferring the ethyl ether solution to a round bottom flask, add four grams of anhydrous magnesium sulfate to remove any soluble water.Filter to remove the solid, and collect the liquid in a clean 250 milliliter one neck round bottom flask. Then remove the ethyl ether and unreacted oliphants using the rotary evaporator to obtain the crude product. Dissolve 2.3 grams of sodium hydroxide in 40 milliliters of deionized water.Add the previously prepared sodium hydroxide solution to the flask containing the crude product, and shake vigorously for five minutes. Following this, add 0.5 molar cobalt chloride solution dropwise while shaking until no more blue precipitate is generated and the solution is pink. Filter the pink solution, and wash the blue precipitate with deionized water until the filtrate is colorless.Then transfer the filter cake back to the flask, and add 100 milliliters of acetone. On the following day, pulverize the blue filter cake using a stainless steel spoon to release any impurities trapped in the bulk. Filter the solid and wash it with 100 milliliters of acetone.After drying the filter cake at room temperature, add 120 milliliters of ethyl ether and 80 milliliters of 10%sulfuric acid solution to the filter cake. Transfer the resulting solution into a 250 milliliter separating funnel, and shake vigorously until the blue precipitate disappears. After removing the bottom aqueous phase, wash the ethyl ether solution several times with 30 milliliters of 10%sulfuric acid solution until the aqueous phase is colorless.Then wash with 80 milliliters of saturated sodium chloride solution until the aqueous phase pH is six to seven. After transferring the ethyl ether solution to a round bottom flask, add four grams of anhydrous magnesium sulfate to remove any soluble water. Filter to remove the solid, and collect the liquid in a clean 250-milliliter one neck round bottom flask.Finally, remove the ethyl ether using the rotary evaporator to obtain the pure product. Phosphorus NMR spectra were collected for the intermediate monoalkylphosphinic acid before and after purification by the amantadine method. During the monoalkylphosphinic acid synthesis, it is difficult to avoid the generation of the dialkylphosphinic acid byproduct, which is the reason for the peak at 62.507 PPM in the spectra.Phosphorus NMR spectra, proton NMR spectra, MS spectra, and FTIR spectra, were collected for the acid product after purification by the cobalt salt precipitation method. Potentiometric titration curves of the acid product indicate that the purity of the product can exceed 96%High-purity nonsymmetric dialkylphosphinic acid can be obtained through this method, which allows exploration of new extractants. This class of extractants can be used to aid the extraction and the separation of rare earth irons, nonferrous metals, rare metals, et cetera.The separation and extraction performance can be fine-tuned by modifying the alkyl chains.

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7.4K vistas.  University of Science and Technology Beijing. The overall goal of this protocol, is to introduce a universal synthetic method for nonsymmetric dialkylphosphinic acid extractants to a free radical addition reaction using sodium hypophosphite as a phosphorus source. The method can for a potential in the hydrometallurgy to develop a new dialkylphosphinic acid extractants. And novel potential extraction and separation with class of extractants.Compared to the traditional method, which use phosphate as a phosphorus source, this method ...