J . Natn. Sci. Coun. Sri Lanka 1998 26(3): 229-233
SHORT COMMUNICATION.
SYNTHESIS AND SPECTROSCOPIC STUDIES OF 4-ADIPOYL-BIS (1
-PHENYL-3-METHYL-PYRAZOLONE-5)
AS A BIS-(1,3-DIKETONE) B.A. UZOUKWU1", H. DUDDECK1 and S.I. OKEKE2lInstitut fir Organische Chernie, ~ n i v e r s i t a t Hannover, Scltneiderberg IB, Hannouer, Germany.
'Environmental Study Unit, Evergreen University, Los Angeles, USA.
(Received: 16 January 1997; accepted: 12 June 1998)
Abstract: I - A d ~ ~ o ~ l b i s (1-phenyl-3-methylpyrazolone-5) has been synthes~sed ancl characterised spectroscopically using UV, IR, NMR and mass spectroscopy.
The compound was synthesised through a condensation reactlon between pyrazolone and adipoyl chloride. The spectral data showed that the compound existed a s a bis (1,3-diketone). Assignments of the IR, NMR, and mass spectral results a r e reported
Key Words: Adipoyl pyrazolone, chelating agents, pyrazolone,spectroscopic clata
INTRODUCTION
1-phenyl-3-methyl-4-acylpyrazolones-5 have been found to possess valuable spectroscopic1-" and extra~tion"~properties for metal ions from aqueous media.
Synthesis of derivatives of the ligand and their application in the extraction of Mn(II)\ Cu(I1) alkaline earth and alkali earth metals6 from aqueous media and in the separation of metal i0ns~9~ from one another have been carried out.
However, the search for new derivatives of this ligand for better selective extraction and cliemico-spectrographic analysis of metal ions continues. Some of the different methods tried included increasing the acidity of the chelating ring by introducing electron withdrawing substituentslO a t the 4-acyl position or increasing the number of the carbon atoms of the 4-acyl substituent. 4-Acylpyrazoloi~es have been characterized as bidentate ligands existing in solution as the ket~enoll.".~
tautomer.
The present study reports the synthesis of the 4-adipoyl derivative which is quadridentate, though a modified method described by Jensen.11 Characterization ofthe ligand spectroscopically showed that unlike other derivatives of 4-acylpyrazolone, it existed as the bis(l,3-diketone) shown in Fig 1.
METHODS AND MATERIALS Experimental:
Sylztlzesis of 4-adipoylbis (1-pkenyl-3-metlzylpyrazolo~~e-5) : The ligand was syntliesised by dissolving 10 g (57.4 mmol) of 1-phenyl-3-methyl-pyrazolone in 100 ml of dioxane in a one-litre 3-neck quick-fit flask carrying a reflw condenser
<Corresponding author-Present address : Department of Pure and Industrial Chemistry, University of Port Harcourt, PMB 5323, Port Harcourt, Nigeria.
B.A. IJzoulzwz~ et. al.
Figure 1: The molecular structure of 4-adipoylbis (1-phenyl.3-methyl-pyra~oloi~e-5).
by warming. Calcium hydroxide (6.g) was added to the solution and the tempera- ture of the suspension raised to 100°C before 4.5 m l ( 3 1 mmol) of adipoyl chlo- ride was added dropwise within 5 min with stirring. After 20 mill of stirring, t h e exothermic reaction mixture changed from green to dull orange. T h e tem- perature of t h e oil b a t h heating t h e reaction mixture was raised to 125°C and stirring continued for another 15 min when the product became a clay brown thick paste.
The thick paste was poured into 400 ml of 4 M HCl solution. Some pieces of ice were added to assist precipitation. The brown solid t h a t settled was filtered off a n d washed i n a suspension of hot ethanol to obtain 83% yield of a light pink fluffy product, m.p=193 O C Anal. Cal.for C,,H,,N,O,:C, 68.1; H,5.7;
N,12.2 found C,68.0;H,5.7;N7 12.0%. When the experiment was carried out a t temperatdres below 80°C, stickly brown products with low yield and of low qual- ity were obtained.
Physical measurements:
The IR spectrum was recorded on a Heydon and Sons Infrared speckophoto- meter, dispersed in chloroform and NaCl windows. The NMR spectrttm was obtained from Bruker Data Systems spectrometer using CDCl, as solvent and reported a s 6 ppm relative to TMS.
Adipoyl Plzenyl Methyl Pyrazoloize 231
UV (assignment): CHCl,, h = 270 nm, E = 7.8 x 104 (~c+~c:I:).
IR (assignment): 1620s ( v ..C=O); 1596s,1460m (phenyl ring v C=C); 1564s, 1392m;
(pyrazole ring stretch); 1500m ( I ) NsCYC4); 1428m (P,,CI-I,I); 1364m ( v ,C=O);
1304m ( v,C--C-C); 1192m, 1076s, 1028m ((3-11 in-plane deformation); 644w, 604w, cm-' (chelate ring vibration).
NMR, 6 (assingment): 1.88 (b, 41-1, -CH,-CI-1,CO-); 2.49 (s, 61-1, -CI-I:,); 2.83 (b, 411, -CO-CI-I,-CII,); 7.29 (s, 2H, pyrazole ring); 7.30 (t, 2H, J = 7.45 Hz, p-Ph);
7.45 (t, 4H, J = 8.0 Hz, m-Ph); 7.83 ppm (d, 411, J = 7.72 Hz, 0-1'11).
MS, m/e (%, assignment): 458 (6, M+); 457 (25, M+-1); 439 (13, (M+-1)-I3,O); 229 (26, M+/2); 201 (Mt/2-C,H,); 175 (79); 91 (37, C,H,N+); 77 (75, C,H,').
DISCUSSION
Tlle synthesis of 4-adipoylbis (lphenyl-3-methyl-pyrazolol~e-5) can be repre- sented. by the condensation reaction shown below.
T h e chelating agcnt can exist in the tautomeric fbrms given in Fig 2,already reported for 4-acylpyrazoloncs'~~~'
T l ~ e ketoenol, structures I and I1 presented i n Fig. 2 are e%i.misatecl nruon.g the possible structures because the IR data did not h.ave vibrat:io~.l.al ti-ecluen- cjes near 3100 cm-' and 2700 cm-' t h a t are assigned" to v 01-1 and 11 O I i . . . O of ketoenol respectively. Proton NMR data presented also do not have any reso- nance signal near 11 ppm usually assigned
"
to OH group of'the ligand. Absence of vibrational frequency bands in the 3100-4000 cm-l 'egion which could. be due to v NH also eliminates the diketone structure IV. That leaves the diketone str~lcture I11 as the form in which kadipoylbis (I-phenyl-3-methyl-pyrazolone-5) is existing.232 B.A. ZJzonkw~r el. al.
Structure I11 is supported by the very strong CO absorption band a t 1620 cm-I
Ketoenol forms Diketone forms
Fiyurc 2 : l'automoric foniis ol' the ligand.
and another strong absorption band of equal intensity at 1564 cm
'
assigned to the pyrazole ring stretch. The chemical shift assignments, spectral lntcgration and multiplicity of t h e rcsonance peaks all supported t h e bis(c1tkctone) struc- t u r e I11 presented in Fig 2. Further evidence of bis(diketone) structural form of 4-adipoylbis(1-phenyl-3-methylpyrazolone-5) is the presence of proton reso- nance signal a s 7.29 ppm (integrated for 2H) due to the two CH- p1.oto11~ of the two pyrazole ring moietles of the ligand.Acknowledgenlent
The authors wish to thank Alexander von Humboldt Foundation for a Research Fellowsl~ip awarded to BAU.
R e f e r e n c e s
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2. Uzoultwu B.A. (1995). Spectrophotometric studies on 4-acyl derivatives of 1-phenyl-3-methylpyrazolone-5 in various solvents. Spectrochin~icn Acta 51A:1081-1082.
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4. Uzoukwu
B.A.
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N.T.
(1970).Extraction of copper (11) and niclccl (11) as their 1-pl~e~lyl-3-methyl-4-ber~zoyl-pyrazolone-5 cl~elates. Jounf,uc! of Ailc~- 1.ytical Cl~,emistr.y,USSR 25: 40-44.8. Bukowslry H., Uhlemanll E., Gloe K. & Muhl P. (1992). Liquid-liquid ex- traction of alkal.ine earth. and a1lral.i metal ions with acyl.pyrazolo.nes.
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