Fadhil S. Kamounah

Roskilde University, Roskilde, Zealand, Denmark

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Publications (49)94.57 Total impact

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    ABSTRACT: Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurements and advanced chemometrics. It has been found that in ethanol and DMSO the enol-amide tautomer is present mainly as a sandwich type dimer. The addition of water leads to distortion of the aggregate and to gradual shift of the equilibrium towards the zwitterionic tautomer. Quantitative data for the aggregation and the tautomeric equilibria are presented. Quantum chemical calculations (M06-2X/TZVP) have been used to explain stability of the tautomers as a function of the solvent and concentration.
    RSC Advances 03/2015; DOI:10.1039/C5RA03653D · 3.71 Impact Factor
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    ABSTRACT: A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-Hydroxy-1-naphthaldehyde a process of concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-Hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the nitrogen of the piperidine nitrogen exists. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform, methylene chloride and toluene the OH form is completely dominant. Both 4-Hydroxy-1-naphthaldehyde and 4-Methoxy-1-naphthaldehyde (fixed enol form) show a dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirms the existence of a cyclic dimer.
    Physical Chemistry Chemical Physics 03/2015; DOI:10.1039/C5CP00870K · 4.20 Impact Factor
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    ABSTRACT: It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)triethanone may be tautomeric. Using 13C NMR chemical shifts and deuterium isotope effects on 13C chemical shifts, it is demonstrated that this is not the case. This compound occurs as a strongly hydrogen bonded benzene structure with hydrogen bonds between OH groups and the acetyl groups in both non-polar and hydrogen donating solvents. Quantum-chemical calculations using MP2 and M06-2X methods show substantial preference for the phenol structure in both the gas phase, and in cyclohexane and methanol. In addition, conventional UV–vis spectroscopy data suggest not tautomeric, but aggregation behaviour of the molecule in methanol and acetonitrile.
    Tetrahedron Letters 01/2014; 55(2):354–357. DOI:10.1016/j.tetlet.2013.11.026 · 2.39 Impact Factor
  • Poul Erik Hansen, Fadhil S Kamounah, Daniel T Gryko
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    ABSTRACT: Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ's) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be negative, indicating transmission via the hydrogen bond. In addition unusual long-range effects are seen. Structures, NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using DFT methods. Two-bond deuterium isotope effects on 13C chemical shifts are correlated with calculated OH stretching frequencies. Isotope effects on chemical shifts are calculated for systems with OH exchanged by OD. Hydrogen bond potentials are discussed. New and more soluble nitro derivatives are synthesized.
    Molecules 04/2013; 18(4):4544-60. DOI:10.3390/molecules18044544 · 2.10 Impact Factor
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    ABSTRACT: 4-((Phenylimino)methyl)naphthalen-1-ol and 4-((phenylimino)methyl)-2-(piperidin-1-ylmethyl)naphthalen-1-ol have been synthesized and their tautomeric properties were investigated using molecular spectroscopy (UV Vis absorption/emission and NMR), X-ray crystallographic analysis and quantum chemical calculations. The results show that with the implementation of a flexible piperidine ring a controlled shift in the tautomeric equilibrium will be achieved upon protonation/deprotonation in acetonitrile. The addition of a metal salt also shifts the tautomeric equilibrium, but at very high concentrations, which is caused not by a complex formation, but a special effect of the salt addition. (C) 2012 Elsevier B.V. All rights reserved.
    Journal of Molecular Structure 03/2013; 1036:267-273. DOI:10.1016/j.molstruc.2012.11.055 · 1.60 Impact Factor
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    ABSTRACT: BACKGROUND: Friedel-Crafts acetylation is an important route to aromatic ketones, in research laboratories and in industry. The acetyl derivatives of 3,3' -dimethylbiphenyl (3,3' -dmbp) have applications in the field of liquid crystals and polymers and may be oxidized to the dicarboxylic acids and derivatives that are of interest in cancer treatment. FINDINGS: The effect of solvent and temperature on the selectivity of monoacetylation of 3,3'-dmbp by the Perrier addition procedure was studied using stoichiometric amounts of reagents. 4-Ac-3,3' -dmbp was formed almost quantitatively in boiling 1,2-dichloroethane and this is almost twice the yield hitherto reported. Using instead a molar ratio of substrate:AcCl:AlCl3 equal to 1:4:4 or 1:6:6 in boiling 1,2-dichloroethane, acetylation afforded 4,4' - and 4,6' -diacetyl-3,3' -dmbp in a total yield close to 100%. The acetyl derivatives were subsequently converted to the carboxylic acids by hypochlorite oxidation. The relative stabilities of the isomeric products and the corresponding sigma-complexes were studied by DFT calculations and the data indicated that mono- and diacetylation followed different mechanisms. CONCLUSIONS: Friedel-Crafts acetylation of 3,3' -dmbp using the Perrier addition procedure in boiling 1,2-dichloroethane was found to be superior to other recipes. The discrimination against the 6-acetyl derivative during monoacetylation seems to reflect a mechanism including an AcCl:AlCl3 complex or larger agglomerates as the electrophile, whereas the less selective diacetylations of the deactivated 4-Ac-3,3' -dmbp are suggested to include the acetyl cation as the electrophile. The DFT data also showed that complexation of intermediates and products with AlCl3 does not seem to be important in determining the mechanism.
    Chemistry Central Journal 06/2012; 6(1):52. DOI:10.1186/1752-153X-6-52 · 1.66 Impact Factor
  • Fadhil S. Kamounah, Peter Christensen, Poul Erik Hansen
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    ABSTRACT: Acetylation of cedarwood oil (Virginia) leads besides acetyl cedrene also to a minor product, 1,7,7-trimethyl-2,3-(3′,4′-dimethylbenzo)bicyclo[3.2.1]octane (follower). This product is identified by 2D NMR. Acetylation of cedarwood oil with 13C-1 labeled acetic acid anhydride leads to a product labeled at the aromatic carbon C-3′. From the 13C-labeled compound 13C-13C coupling constants could be measured.Acetyl cedrene is conveniently deuteriated by an acid-catalysed exchange reaction using trifluoroacetic anhydride and D2O. The product is found to be deuteriated both at the acetyl group and at the methyl group at the double bond (carbon 6).The reaction condition during deuteriation of cedrol leads to the elimination of the hydroxyl group at C-6 with the formation of α-cedrene deuteriated at H-5 and the methyl group at C-6.Deuteriation of the follower leads to deuterium exchange at the aromatic carbons C-5′ and C-6′. Copyright © 2010 John Wiley & Sons, Ltd.
    Journal of Labelled Compounds 03/2011; 54(3). DOI:10.1002/jlcr.1830
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 08/2010; 28(32). DOI:10.1002/chin.199732141
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 06/2010; 27(26). DOI:10.1002/chin.199626163
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    ABSTRACT: Attachment of molecules and proteins to surfaces is of great interest for the development of a large variety of applications. We present herein a novel approach to efficiently couple a molecule of choice to biological building blocks. We synthesized and employed a new derivative of 5-bromo-7-nitroindoline to attach nucleophilic molecules and proteins to gold surfaces by photochemical activation. The reaction can be seen as a photoactivated alternative to the activated ester type chemistries that are commonly used to attach proteins or molecules to surfaces. We characterize the reaction by UV-vis and NMR spectroscopy, and as test of principle experiment, we show that we can attach proteins to surfaces and demonstrate that we can functionalize gold nanoparticles by this optically induced cross-linking reaction.
    Bioconjugate Chemistry 06/2010; 21(6):1056-61. DOI:10.1021/bc900561m · 4.82 Impact Factor
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    ABSTRACT: Alkylated hydroxyflavothiones, namely flavothione, 5-hydroxyflavothione, 5,7-dihydroxyflavothione (chrysinthione), 7-dodecyloxy-5-hydroxyflavothione, 7-butyloxy-5-hydroxyflavothione, 2',3,4',7-tetramethoxy-5-hydroxyflavothione, 3,3',4',7-tetramethoxy-5-hydroxyflavothione, 7-butyloxy-4',5-dihydroxyflavothione and 7-butyloxy-4',5-hydroxyflavanonethione have been synthesized from the corresponding hydroxyflavones in two steps, alkylation of the non-hydrogen-bonded hydroxyl groups by bromoalkanes or dimethyl sulfate followed by conversion of the carbonyl group to a thione using Lawesson's Reagent under microwave irradiation and solvent-free conditions. Part of the alkylated flavanone, 7-butyloxy-4',5-dihydroxyflavanone, was oxidized during the treatment with Lawesson's reagent to yield a second product 7-butyloxy-4',5-dihydroxyflavothione in addition to the target product butyloxy-4',5-hydroxyflavanonethione. Deuterium isotope effects on 13C chemical shifts have been measured in hydroxyflavones, isoflavones, flavanones and the thio analogs. Formal four-bond deuterium isotope effects on 13C chemical shifts, nDeltaC=S(OD) are very sensitive to variations in structures and substitution patterns. Density functional theory (DFT) calculations are carried out to obtain geometries. Correlations relating distances around the hydrogen bond system to the deuterium isotope effects on 13C chemical shifts are discussed. 13C chemical shifts are calculated by DFT methods. Effects of thiocarbonyl anisotropies are suggested.
    Magnetic Resonance in Chemistry 12/2009; 47(12):1043-54. DOI:10.1002/mrc.2510 · 1.56 Impact Factor
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    ABSTRACT: The solid state tautomerism of 2-((phenylimino)methyl)naphthalene-1-ol was studied using X-ray measurements and absorption spectroscopy. In the solid state, the keto tautomer predominates. The observed shift in the equilibrium from the enol (dilute solution) to the keto (solid state) forms is explained by the formation of dye aggregates using ab initio quantum chemical calculations.
    Dyes and Pigments 10/2009; 83:121. DOI:10.1016/j.dyepig.2009.04.002 · 3.47 Impact Factor
  • A. Filarowski, A. Kochel, M. Kluba, F. S. Kamounah
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    ABSTRACT: The synthesis and X-ray measurements of four Schiff bases were carried out at 100 K. The HOMA and HOSE aromaticity indices were estimated on the basis of the experimental data. The aromaticity of the phenyl ring and the chelate chain was analysed. A comparison of the aromaticity of naphthalene and phenyl derivatives of hydroxy aryl Schiff bases is presented. The balance between the aromaticity of adjacent rings of the naphthalene fragment and its effect on proton transfer is defined. Research on the interrelations between aromaticity and the intramolecular proton transfer in hydroxy aryl Schiff bases is shown. Copyright © 2008 John Wiley & Sons, Ltd.
    Journal of Physical Organic Chemistry 11/2008; 21(11):939 - 944. DOI:10.1002/poc.1403 · 1.23 Impact Factor
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    ABSTRACT: Friedel-Crafts acetylation of 9H-fluorene is an effective route for the preparation of mono- and diacetyl-9H-fluorenes. Using acetylchloride as the reagent and aluminum chloride as the Lewis acid catalyst the effect of the solvent polarity, the temperature, the reaction time and the mode of addition (Perrier or Bouveault) on the reactivity-selectivity pattern was investigated. The results showed that monoacetylation of 9H-fluorene in chloroalkanes and nitromethane gives mixtures of 2-acetyl- and 4-acetyl-9H-fluorene with the former dominating. In addition to these two isomers, 2,7-diacetyl-9H-fluorene was obtained in 5-11 % yield when carbon disulfide was used as the solvent. Acetylation of 9H-fluorene in dichloroethane and carbon disulfide, using an excess of acetyl chloride and aluminum chloride at reflux temperature, gives 2,7-diacetyl-9H- fluorene exclusively in high yields (> 97%). Attempts to carry out diacetylation in nitromethane on the other hand resulted in the formation of monoacetyl derivatives only. The ketones obtained were isolated and identified by various physico-chemical techniques. The 1 H NMR spectrum of 4-acetyl-9H-fluorene is reported for the first time. Values of the total energies and the Gibbs free energies at 298K for 9H-fluorene, the five isomeric monoacetyl-9H-fluorenes and the four σ- complexes leading to 1-, 2-, 3- and 4-acetyl-9H-fluorene, respectively, were computed at the DFT B3LYP 6-31G** level of theory. The data serve as a basis for the discussion of the reactivity-selectivity pattern observed and it is concluded that the distribution of products is partly kinetically controlled.
  • Poul Erik Hansen, Fadhil S. Kamounah, Saif Ullah
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    ABSTRACT: o-Hydroxyaromatic esters, β-hydroxyketoesters, Meldrums acids, other o-hydroxyesters and a few o-hydroxyacid anhydrides are investigated by deuterium isotope effects on 13C chemical shifts, xΔC(OD). Especially the ester carbons show unusual deuterium isotope effects. A principal component analysis based on bond lengths and distances around the hydrogen bond six-membered ring make it possible to predict isotope effects. The ratio nΔCO(OD)/2ΔC(OD) can be used to predict the extent of transmission via the hydrogen bond. Furthermore, deuterium isotope effects can be used to gauge possible tautomerism.
    Journal of Molecular Structure 11/2007; 844:300-307. DOI:10.1016/j.molstruc.2007.06.012 · 1.60 Impact Factor
  • Salam J. J. Titinchi, Fadhil S. Kamounah, Hanna S. Abbo
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    ABSTRACT: Shape selective acetylation of 4,4′-dimethylbiphenyl using anhydrous aluminum chloride as catalyst is an effective route for the production of mono- and di-acetyl-4,4′-dimethylbiphenyl. Preparations, characterization and a catalytic study of the Friedel-Crafts acetylation of 4,4′-dimethylbiphenyl, involving use of the Perrier addition procedure are carried out in a range of solvents and under a variety of experimental conditions. The obtained ketones are isolated and identified by various physico-chemical techniques. Mono acetylation of 4,4′-dimethylbiphenyl afforded a mixture of two isomeric acetyl dimethylbiphenyls. In chloroalkane or carbon disulfide solvent, the yields of isomers were in the order: 2->3-; in nitromethane 3-isomer predominated. On the other hand diacetylation of the hydrocarbon gave only the 2,3′-diacetyl isomer. The mono- and di-ketones are converted to the corresponding carboxylic acids. 2-Acetyl-4,4′-dimethylbiphenyl was prepared by indirect multi-step synthetic routes. 3-D molecular modelling supports the positional assignment of the acetyl group with the results obtained from the electronic spectra.
    Journal of Molecular Catalysis A Chemical 08/2007; 273(1):169-176. DOI:10.1016/j.molcata.2007.03.069 · 3.68 Impact Factor
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    ABSTRACT: The aim of the current report is to shed light on the tautomerism of 4-((Phenylimino)methyl) naphthalene-1-ol in solution, which was studied by UV-Vis spectroscopy and quantum chemical calculations. It was found that this compound does not have the typical tautomeric behavior of its analog 4-Phenylazo-naphthalen-1-ol. The complicated equilibrium between the enol- and keto-like forms and two kinds of dimers that can exist in solution, is strongly dependent on the proton acceptor/donor abilities of the solvent. Using advanced data treatment quantitative information about the tautomeric and dimeric equilibrium constants was obtained. Copyright # 2007 John Wiley & Sons, Ltd.
    Journal of Physical Organic Chemistry 05/2007; 20(5):313 - 320. DOI:10.1002/poc.1143 · 1.23 Impact Factor
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    ABSTRACT: Tautomerism in aromatic systems with oxygen substitutents is rare. This is investigated in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (1) and in 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (2). The tautomeric nature of 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene is supported by long-range hydrogen-hydrogen coupling between the OH-1 and the OH-8 and by the isotope effects on 13C caused by deuteration at the CH3C==O methyl group. Compound 2 participates in a degenerate equilibrium between two equivalent nonsymmetrical rotamers (2A and 2B), each having two intramolecular O...HO hydrogen bonds: one involving an acetyl oxygen and the neighboring hydroxyl group, and the other between the oxygen centers at positions 1 and 8. In addition, each rotamer is involved in a tautomeric equilibrium, with a structure having an OH-substituted exocyclic double bond (2AT or 2BT).DFT calculations for a large set of compounds highlight the factors controlling the unusual rotational and tautomeric behaviors. A very important factor seems to be the repulsive interaction between the O-1 and O-8 centers, which is modulated by formation of an OH-1...O-8 or OH-8...O1 hydrogen bond. Steric interactions, mesomeric release of electrons from the oxygen at position 8, and a strong OH...O...C hydrogen bond are other factors.Solid-state 13C NMR spectra of 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene at different temperatures demonstrated no averaging in the solid, whereas partially deuterated 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene showed an isotope effect at C-1 of 1.5 ppm, indicating tautomerism in the solid state.
    Magnetic Resonance in Chemistry 02/2007; 45(2):106-17. DOI:10.1002/mrc.1925 · 1.56 Impact Factor
  • Salman R. Salman, Fadhil S. Kamounah
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    ABSTRACT: Enol-Keto tautomerism in a new novel series of naphthylidineaniline Schiff bases were studied using their mass spectrum. Two model compounds, namely, salicylidineaniline (Model compound 1, series 1) and naphthylidinequinolinamine Schiff base (Model compound 2, series 4) were used to represent the enol and the keto forms. The mass spectra of the novel series (compounds 4–12) (series 3) are compared with compound 3 which is a representative compound of series 2. The mass spectral measurements reveal the fragmentation pattern in all the new series compounds. It was found that the fragmentation in the new series (series 3) resembles that of the series 2.
    Spectroscopy Letters 08/2006; 35(3)(327–335 (2002)):327-335. DOI:10.1081/SL-120005669 · 0.72 Impact Factor
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    ABSTRACT: Linear (one-photon) and nonlinear (two-photon) spectral properties of 4-N,N-dimethylamino-4′-aminoazobenzene have been investigated under protonation in DMSO/water solvent mixtures. Observed spectral changes have been discussed in terms of ammonium–azonium tautomerism. The corresponding tautomeric constants have been determined for the first time for such kind of tautomeric equilibria. The process of protonation leads to changes of the two-photon absorption properties, suggesting that such process could be used as a tool for change of third-order nonlinear optical activity in solution.
    Journal of Photochemistry and Photobiology A Chemistry 07/2006; 181(2):274-282. DOI:10.1016/j.jphotochem.2005.07.025 · 2.29 Impact Factor

Publication Stats

781 Citations
94.57 Total Impact Points


  • 2005–2014
    • Roskilde University
      • Department of Science, Systems and Models (NSM)
      Roskilde, Zealand, Denmark
  • 1996–2001
    • IT University of Copenhagen
      København, Capital Region, Denmark
  • 1985–1992
    • University of Basrah
      • Department of Chemistry
      Omolgasr, Muḩāfaz̧at al Başrah, Iraq