Indiap Journal of ChemistryVol. 23A, June 1984, pp. 537-538

o-Cyanobenzoylacetanilide as anAnalytical Reagent for Uranium(VI)

MOHAMED M SHOUKRY

Department of Chemistry, Faculty of Science. Cairo University,Giza, Egypt

Received 25 March 1983; recised and accepted to 6 March 1984

Reaction of o-cyanobenzoylacetanilide with uranium(VI) hasbeen studied and the complex obtained has been characterised on thebasis of analytical data, electrolytic conductance and IR spectra. Theligand has been found to be suitable for gravimetric determination ofuranium(VI). The complex is precipitated quantitatively in the pHrange 6.0-8.0; its separation from a large number of metal ions isdescribed.

A critical examination! of the important gravimetricmethods for the determination of uranium(VI)indicates that the reagents used are mostly oxygen-containing and the complexes formed are often ofindefinite compositions or the procedures have poorselectivities. Among the reagents used for thegravimetric determination of UO~ + is benzoylacetani-1ide(BA). However, composition of the precipitateformed depends on experimental conditions+",Benzoylacetanilide has been reported? to react withUO~ + as an enolate. It occurred to us that a derivativeof(BA) with a substituent that enhances the formationof the enolate would improve the chelatingpotentiality. In the present investigation the UO~ +

complex of a-cyanobenzoylacetanilide(1) has beensynthesised and investigated by physicoanalyticaltechniques. The complex formation reaction has beenutilized for the gravimetric determination of UG~ ".Previously, we have reported'v" the use of (1) as ananalytical reagent for iron(II1).

Solution of uranyl nitrate (AR grade) was preparedin triply distilled water and standardised by standardprocedures". Aqueous solutions of diverse ions wereprepared from the nitrates or chlorides. 'l.-

Cyanobenzoylacetanilide(l) was prepared frombenzoylacetonitrile and phenyl isocyanate using theprocedure reported":" earlier (yield, 85~~o)'Solution ofthe reagent was prepared in I: I ethanol-dioxanemixture.

pH measurements were carried out on a Pye UnicumpH -meter. The IR spcctr.. (K Br) were recorded on:\ICOLET 7i99-FTiR spcc t ro p hot o mc te r .Electrolytic conductance was measured at ~5 1:('.02 Cusing a WTW LBR conductivitv meter Magneticsusceptibility measurements were carried out using a

"Galilee-Sartorius" air damped analytical balance.Preliminary investigation showed that the optimum

conditions for complete precipitation of the complexwere: pH, 6.0-8.0 and reagent concentration 2-3 timesthe amount of metal ion taken in solution.

o-cyanobenzoylacetanilide can exist in any of thepotentially tautomeric structures Ia-Id. Structure Iaseems to be the most likely in the solid state on the basisof its IR spectrum. In a previous publication", the p K;of the ligand was determined to be 3.40. This acidic p K,indicates that in solution phase the enol forms Ib, Ieand/or the resonance hybrid Id are predominant.

o 0II II

Ph- C C<,CH»< >; NHPh

ICN

o OHII I

Ph- C C<, C"""" <, NHPh

ICN

Ib10

OH 0I II

Ph-C C<, c -r >: NHPh

ICN

Ie

O/H··,O

I: :1Ph-C', )C

...::.'( .......••.. NHPh

ICN

Id

Composition ofthe complexAnalytical data of the solid complex show the

stoichiometry of the complex to be I: 2 (metal: ligand).The electrolytic conductance in DMF at 25' (AM 8n 1 ern", cone. = 0.00 I M), indicates the nonelec-trolytic nature of the complex and nonprotonatedform of the ligand in the chelating species.

Regarding the mode of chelation, there are threepossible structures (l la-IIc).

~/2 UOzI2,/ .•...... /' ..•...

o 0 0 NHPh

I: ;11: ;1Ph-C', •. 'C Ph-C. __'Co

"( NHPh "c .I I

CN CN

UOzI20...... <,

I: ,N

Ph-C' "o~"-c'#/1

CONHPh

IJo IIb lIe

IR spectrum of the ligand exhibits a broad band atJ635 ern -I, characteristic of benzoyl and anilidecarbonyl groups. On chelation with uranyl ion thisband disappears which indicates that coordinationoccurs through the two oxygen atoms as in lIa anddoes not involve either the anilide nitrogen atom (lIb)or the cyano group (I Ic). The presence of the uranium-oxygen covalent bond in the complex was established.The complex exhibits a very strong band ~H930 em 1

537

INDIAN J. CHEM., VOL. 2JA, JUNE 1984

characteristic of asymmetric stretching of uranyl ion inaccordance with the earlier+? observation in manyuranyl complexes (900-950 em -I). The magneticsusceptibility measurements showed the complex to bediamagnetic as expected for 5.f configuration.

Procedure for gravimetric determination of U022+

An aliquot containing 10 to 60 mg of metal ion washeated to 70-80°. The reagent solution of con-centration 2-3 times that of uranyl ion was then slowlyadded with constant stirring. The pH of the mixturewas raised to 6.0-8.0 by the addition of ammoniumhydroxide solution (1 :4). The complex was pre-cipitated and digested on a water bath for 30 min andthen filtered through a sintered-glass crucible(G4),washed with water and finally with ethanol-watermixture (1: I). It was weighed as UOz{CI6HIIN202hafter drying at II 0-130°C. The complex was crystallineand yellow in colour [Found: C,47,97; H, 3.13;N, 6.87;for U02(CI6HllN202)2 Reqd.; C,48.24; H, 2.76; N,7.03%].

Effect of diverse ionsCu(ID, Co(ll) , Ni(II), Zn(II), Mn(ll), Sr(ID, Ba(II),

Pb(II), Hg(II), Al(III), Th(IV), Zr(IV) and Bi(III)

538

interfere in the estimation of U022+ by the presentreagent. However, these ions can be completelymasked by adding magnesium-EDTA solution to thetest solution, so that the total EDT A content is aboutfive times the total concentration of the diverse ionspresent.

The present method has the advantage of beingreproducible and precise as indicated by the low valueof the standard deviation (0.11) for determination ofsolutions containing 30 mg uranium (10determinations).

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69 (1979) 211.5 Shoukry M M, Mahgoub A E & Elnagdi M H, Ann Chim (Rome),

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