Makhijani, Santosh D.

Sangal, Satendra P.

English

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----------~---1INOTESTABLE 1- IRREVERSIBILITYANDKINETIC PARAMETERDATA[Tryptophan]E314-El/4By Meitesand Israel treatment(mM) cxnaLlGtkl"(kcal)10·130,5728·902·3X 10-1120 69 4953'31'34-6 2457 57 051 40 58,06' 9 386'70 ,60' 15 -81-639x98' -100'4 2X 0-115,2·*cxis derived from the relation E314-E114=0'0564focnand cx<0'5 at n=2 is regarded as a condition for totalirreversibility11.that the slopeincreasedsignificantlyrenderingtheelectrodeprocessfrom near reversibleto totallyirreversible(Table 1), indicateda changein basicnatureof the reactionard in analogywith Ni(II)-tryptophansystemit can be concludedthat thefirst wave correspondsto anirreversiblereductionof Zn(II)-tryptophan complex.Similar to Ni(II)-tryptophansystemreportedby Lal andChristian4thereis a secondwavealsobut it is maskedby amaximiumatlower[tryptophan].Theroleofaminoacids as maximiumsuppressors2is alreadyknownandasthe [tryptophan]is increasedin the presentstudy the maximiumgradually disappearsandthe secondwavecan be observed.However,theconcentrationof the maximiumsuppressor(i.e.tryptophan)at this stageis ratherhigh (7X to-3M)and possiblybecauseof this the height of thesecondwave is very much reducedrenderingareliable quantitativestudy of this secondwaveat this stagedoubtful. At 20 mM tryptophanit iscompletelyeliminated.Studiesregardingtheorigin,natureandkineticsof this waveunderalternativeexperimentalconditionsarein progress.The positive shift of the Et (first wave) at[tryptophan]>6 mM may be attributedto thedouble layer effectlO due to high [tryptophan].Tryptophanbeingchargedspeciesin solution(duetozwitterionformation)andalsosurface-activeis quitelikely to bring changesin doublelayer structurewhichmayleadto a positiveshift in Et·Authors are thankful to the Principal, AgraCollege,Agra, for providingthenecessaryfacilities.References1. QUINTIN, M. & FOGLIZZO,R., c.r. hebd.Acad. Sci. Ser.C., 262 (1966),1500.2. PLETICHA, R., Colln Czech.chem.Commun.,15 (1950),807; Chem.Listy, 45 (1951),185.3. CHANDRA,S. & SRIVASTAVA,S. N., Indian]. Chem.,7(1969),829.4. LAL, S. & CHRISTIAN,G. D., J. prakt. Chem.,313 (1971),99.5. JHA, S. K., JHA, S. & SRIVASTAVA,S. N., Z. Naturforsch.,30b (1975),859.6. ROBINSON,R. A., Electrolytesolutions (Butterworths,London), 1955,33.7. CHATURVEDI,R. K., Physico-chemicalstudiesonmurexide,Ph.D. thesis,Agra University, Agra, 1960.8. MEITES, L., PolarograPhictechniques(IntersciencePub-lishers),1965,239.9. STRASSNER,J. E. & DELAHAY, P., J. Am. chem.SQC.,74 (1952),6232.10. MEITES, L., PolarograPhictechniques(IntersciencePub-lishers),1965,291.11.GOTO, R. & TACHI, I., Proc. Intern.PolarograPhyCongr.,Prague,Vol.1(HrirodovedeckeVydavatelstvi,Prague),1951.69.ThermodynamicFunctions& StabilityConstantsof SomeRare Earths withPhloroglucinolSANTOSHD. MAKHIJANI* & SATENDRAP. SANGALtLaxminarayan Institute of Technology, NagpurReceived27 August 1976;accepted12 January 1977StabilityconstantsofthecomplexesofphloroglucinolwithSc(III),Y(III), La(III), Ce(III),Pr(III) andNd(III)havebeenevaluatedin aqueousmediumat J1=O·02M(NaCI04), employingBjerrum-CalvinpH-titrationtech-nique,asusedby IrvingandRossoW. Thevaluesofoverallchangesin free energy(LlG), enthalpy(!i.H)andentropy(LlS) accompanyingthecomplexformationhavebeenreported.The order of stabilitycons-tant is Sc(III)>Y(III)>La(III) and La(III)<Ce(III)<pr(III) <Nd(III).IN this note the thermodynamicfULctionsandstability constants of some rare earths withphloroglucinolhave been evaluatedin aqueousmedium.Themethodsusedwerethesameas describedinpreviouscommunications1,2.The practicalproton-ligandstabilityconSlantsandmetal-ligar,dstabilityconstantsat various temperatureswere obtainedemployingBjerrum-CalvinpH-titrationtechrique3,4,as usedby Irving and Rossotti5.All the chemicalsusedwereof AR grade. Thestocksolution(O'OlM) of phloroglucinol(E. Merck)was preFaredin CO2-freedoubly distilled water.All other solutiors werepreFaredas describedinprevious papers1,2. Titratiols were carried outunder N2 atmosphereand temperaturewasmain-tainedwith an accuracyof ±0·10c.Titrationswerecarriedout with Q'909M NaOHas in previouspapers1,2at (J. =0'02M (NaCl04);total volumewas 100ml.The proton-ligandandmetal-ligandstabilityCon-stants were calculatedas describedin previouspapers1,2. Thevaluesofstabilityconstantsobtainedby interpolationat half n-values5methodaregivenin Table 1.The temperaturecoefficientandGibbs-Helmhc>ltzequationwereusedto determinetheoverallchangesin free energy(LlG), enthalpy(LlS) , and entropy(LlS). The total freeenergychangewas obtainedfromthe equationLlG =- RT ln ~,where~is the*Present address: National Environmental EngineeringResearchInstitute, Nehru Marg, Nagpur 440020.tAuthor to whom correspondencemay be addressed.565INDIAN J. CHEM., VOL. 15A, JUNE 1977TABLE 1 - PROTON-LIGAND AND METAL-LIGAND STABILITYCONSTANTS AT VARIOUS TEMPERATURES[[.L=0·02M (NaCIO.)]Metal Temp. (DC)--------------20 30 40log K;; 11·54 11-12 10·75log K!;' 9·17 8·94 8·74log K;: 8·41 8·17 7·97Sc(III) log KI 15·07 15·27 15·50Y(III) log KI 7·92 8·10 8·30La(III) log KI 6·08 6·25 6·40Ce(III) log KI 6·20 6·37 6·52Pr(III) log KI 6·68 6·85 7·10Nd(III) log KI 6·92 7·12 7·25TABLE 2 - VALUES OF THERMODYNAMIC PARAMETERS OFCOMPLEXATION REACTIONS[[.L=0·02M (NaCIO.)]Metal Temp. D.G D.H D.S°C kcal motc ? kcal mole ? cal deg-1mole"!Sc(III) 20 -20·33830 -21,311 +5·027 +86'92440 -22,346Y(III) 20 -10·68930 -11·304 +5'112 +54'17840 -11·966La (III) 20 -8·20630 -8·723 +7-321 +51'25940 -9'227Ce(III) 20 -8,36830 -8,890 +7·370 +53·66340 -9·400Pr(III) 20 -9·01830 -9·546 +5'973 +51·21840 -10·236Nd(III) 20 -9·33930 -9·937 +7'925 +58·95040 -10·596overall stability constant. The values of enthalpychanges (liH) were obtained by plotting log ~against liT, and equating slope of the linear plotto -liHI4·57. Overall entropy. changes (liS) ofthe reactions were evaluated from the equationliS = (liH-liG)IT.All the thermodynamic parameters so obtainedare given in Table 2.The proton-ligand stability constants decreaseas the temperature increases. The values of n inall the cases were found to be less than 1which showsthat only 1:1 complex is formed.The data in Table 1 show that as the temperatureincreases, metal-ligand stability constant increasesand also stability decreases as the ionic radiiincrease. The order of stability constants in Sc(III)> Y(IlI) > La(IIl) and La(IIl) < Ce(IIl) < Pr(IlI)< Nd(III)'Although liH values in all the cases are positive,the larger positive entropy changes make thecomplexes stable.566References1. MAKHIJANI, S. D. & SANGAL, S. P., J. Indian chem, Soc.,52 (1975), 788.2. MAKHIJANI, S. D. & SANGAL, S. P., J. Indian chem. Soc.,53 (1976), 448.3. BJERRUM, J., Metal ammine formation in aqueous solution(Haase, Copenhagen), 1941, 133.4. CALVIN, M. & 'WILSON, K. W., J. Am. chem. Soc., 67(1945), 2003.5. IRVING, H. & ROSSOTTI, H. S., J. chem. Soc., (1953), 3397;(1954), 2904.Ternary Cu(II) & Ni(II) ComplexesContaining Aromatic AldiminesRAKESH K. KOHLI & P. K. BHATTACHARYAChemistry Department, Faculty of ScienceM.S. University, Baroda 390002Received 17 May 1976; accepted 17 December 1976Reactions of aromatic amines with the mixed Schiffbase complexes of the type MLL', where M = Cu(II)or Ni(II); L = salicylaldimine and L'= 2-hydroxy-I-naphthaldimine, have been carried out. The newmixed Schiff base complexes (I-III) have also beensynthesized by treating the equivalent amounts ofpreformed Schiff bases of salicylaldehyde and2-hydroxy-l-naphthaldehyde with aromatic amineswith an equivalent amount of the metal salt solution.The complexes of the type [M(A(N-N)]+ClO,-,whereM = Cu(II), A = Schiff base of saficyldehyde withaniline and N,N-dipyridyl or o-phenanthroline, havealso been prepared. The complexes have beencharacterized on the basis of elemental and TLCanalyses, conductance, magnettc moment and spectraldata.WE have recently reported! the formation ofmixed ligand complexes of the type MLL',where M =Cu(lI) or Ni(lI), L =salicylaldimine, andL = 2-hydroxy-1-naphthaldimine. In. the presentinvestigation, transamination reactions were carriedout by reacting such mixed Schiff base complexeswith aromatic amines. The mixed Schiff basecomplexes were also prepared by treating Cu(lI)or Ni(lI) salts with preformed Schiff bases derivedfrom salicylaldehyde and 2-hydroxy-1-naphthalde-hyde with aromatic amines.The mixed Schiff base complexes of Cu(lI) orNi(lI) containing one mole each of salicylaldimineand 2-hydroxy-1-naphthaldimine were prepared asreported earlier". Other chemicals, namely aniline,0-, m- and p-toluidines used were of analar grade.UV (CHC13) and IR (nujol) data of the complexeswere recorded on Beckmann DUZ and BeckmannIR-20 spectrophotometers, respectively. Conducti-vity measurements were carried out in CHC13 andH20 on a Toshniwal conductivity bridge typeCLOI01A. Except for the two Cu(lI) complexes(IVa, b) where CI04: happens to be in the outersphere, the molar conductances of all other com-plexes showed them to be non-electrolytes.The UV absorbance of (N-phenyl-salicylaldiminato)(4'-methyl-N-phenylsalicylaldiminato)Cu(1I) (lIa) wasfound to lie between those of bis(N-phenyl-salicyl-

Thermodynamic Functions & Stability Constants of Some Rare Earths with Phloroglucinol

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Thermodynamic Functions & Stability Constants of Some Rare Earths with Phloroglucinol

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