SYNTHESIS AND SPECTROSCOPIC STUDIES OF 4-ADIPOYL-BIS ( 1-PHENYL-3-METHYL-PYRAZOLONE-5 ) AS A BIS-( 1 , 3-DIKETONE )

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 are reported


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 at 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.11Characterization 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  by warming.Calcium hydroxide (6.g) was added to the solution and the temperature of the suspension raised to 100°C before 4.5 ml(31 mmol) of adipoyl chloride was added dropwise within 5 min with stirring.After 20 mill of stirring, the exothermic reaction mixture changed from green to dull orange.The temperature of t h e oil bath heating the 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 and washed in 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;N712.0%.When the experiment was carried out a t temperatdres below 80°C, stickly brown products with low yield and of low quality were obtained.

Physical measurements:
The IR spectrum was recorded on a Heydon and Sons Infrared speckophotometer, 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.
B.A. ZJzonkw~r el.al. Structure I11 is supported by the very strong CO absorption band at 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 the rcsonance peaks all supported t h e bis(c1tkctone) struct 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 resonance signal as 7.29 ppm (integrated for 2H) due to the two CH-p1.oto11~ of the two pyrazole ring moietles of the ligand.