非極性溶媒中のトリフルオロアセチルアセトンによるバナジウム(III)の液-液分配平衡

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書誌事項

タイトル別名
  • Liquid-liquid partition equilibrium of vanadium(III) with trifluoroacetylacetone in nonpolar solvents.
  • 非極性溶媒中のトリフルオロアセチルアセトンによるバナジウム（ＩＩＩ）の液‐液分配平衡
  • ヒ キョクセイ ヨウバイチュウ ノ トリフルオロアセチルアセトン ニ ヨル バ

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説明

The extraction equilibrium of vanadium(III) has been studied with 0.0030.1 mol dm-3 trifluoroacetylacetone (Htfa) in heptane and benzene at pH 13 and ionic strength 0.1 mol dm-3 under an argon atmosphere. An aqueous vanadium(III) solution was prepared by reducing vanadium(IV) with sodium dithionite in aqueous solution. The extracted chelate was confirmed to be V(tfa)3 and the extraction constant (Kex) determined; log Kex was 2.79 in heptane and 2.40 in benzene. The distribution constant of the chelate, PM, was separately determined by the back extraction technique. A heptane solution containing 3×10-3 mol dm -3 V(tfa)3 and 0.4 mol dm-3 Htfa was equilibrated for 30 s with an aqueous solution at pH 4.14.2. The log PM, 3.66, was obtained in heptane and used for the calculation of the overall formation constant, β3. The log β3 was calculated to be 15.68 using the relation of Kex=PMβ3 KHA3/PHA3, where KHA and PHA are the acid-dissociation constant and the distribution constant of Htfa respectively. As the β3 was determined, the PM in benzene could be readily calculated from the Kexvalue, i.e., log PM=5.31. These equilibrium constants obtained were compared with those of tris(acetylacetonato)vanadium(III) (V(acac)3) previously studied. The Kexvalues of V(tfa)3 are 1001000 times larger than those of V(acac)3. This difference was discussed considering the equation for keto-enol tautomerism of β-diketones, Kex= PMβ3 KHE3/PHE3, in which the subscript, HE, stands for the enol. It was concluded that the term PM/PHE3 for V(tfa)3 was close to zero and much larger than that of V(acac)3.

収録刊行物

  • 分析化学

    分析化学 43 (12), 1163-1168, 1994

    公益社団法人 日本分析化学会

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