Fadhil Kamounah - Academia.edu (original) (raw)
Papers by Fadhil Kamounah
Journal of Labelled Compounds and Radiopharmaceuticals, 2011
ABSTRACT Acetylation of cedarwood oil (Virginia) leads besides acetyl cedrene also to a minor pro... more 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.
Phys Chem Chem Phys, 2003
ABSTRACT
Spectrosc Lett, 2002
Enol-Keto tautomerism in a new novel series of naphthylidi-neaniline Schiff bases were studied us... more Enol-Keto tautomerism in a new novel series of naphthylidi-neaniline 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) ...
Spectroscopy Letters, Aug 19, 2006
... Hansen PE, Duns F., Schmitt P. Org. Magn. Reson. 1982, 18,58. Page 8. 666 KAMOUNAH ANDSALMAN ... more ... Hansen PE, Duns F., Schmitt P. Org. Magn. Reson. 1982, 18,58. Page 8. 666 KAMOUNAH ANDSALMAN 12. Salman SR, Kanber SK, Arsalan KL Spectrosc. Letters 1991, 24(9), 1153. 13. Salman SR, Farrant RD, Lindon JC Spectrosc. Letters 1991, 24, 1071. 14. ...
The Journal of Physical Chemistry a, Sep 1, 2004
The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T an... more The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T and ∆S T , of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy. Polar solvents shift the equilibrium toward the quinone form (for the unsubstituted derivative 1c, K T ) 0.20 (cyclohexane) and K T ) 1.49 (ethanol)). Both donor (MeO, NMe 2 ) and acceptor (CN, NO 2 ) substituents lead to a decreased K T independent of solvent polarity. In apolar solvents, for all derivatives 1a-1e, the enol imine a enaminone equilibria are endergonic but exothermic. Linear solvation energy relationships allow extrapolation of ∆G T to the gas phase. Density functional theory calculations (B3LYP/6-311+G**) yield good agreement with these extrapolated ∆G T values. Solvent effects on 1c are also successfully reproduced by the calculations. Geometric (O‚‚‚N distance) and energetic criteria (conformer energy differences, homodesmotic reactions) establish the importance of intramolecular hydrogen bonding for the tautomerism of these compounds. The results obtained for 1a-1e are compared with tautomeric properties of the isomeric naphthaldehyde anils 2-4, the monocyclic analogues 5 and 6, the corresponding azo derivatives 7-9, and the N-alkyl derivative 10.
Spectrosc Lett, 1990
The O‒H…π interaction between proton donor systems phenol, substituted phenols, benzyl alcohol an... more The O‒H…π interaction between proton donor systems phenol, substituted phenols, benzyl alcohol and cyclohexanol and proton acceptor systems benzene, toluene, m- and p-xylenes, naphthalene and anthracene have been studied by infrared spectroscopy. It is found that the strength of the O‒H…π hydrogen bonding decreases in the following order: phenol > benzyl alcohol > cyclohexanol, and phenol > cresol> 2,6-dimethyl phenol > 2,4,6-tri-tret&utyl phenol. The strength of the proton acceptors, on the other hand, decreases in the fol lowing order: xylene > toluene > benzene > chlorobenzene, and for polyaromatic bases the trend is benzene > naphthalene > anthracene.
Bioconjugate Chemistry, Jun 16, 2010
Attachment of molecules and proteins to surfaces is of great interest for the development of a la... more 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.
Spectroscopy Letters, Sep 23, 2006
Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE F... more Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE Fadhil S. Kamounah Chemistry Department, College of Education, University of Sasrah, Basrah, Iraq Sawsan H. Shawkat and Salman R. Salman* ...
Journal of the Chemical Society, Perkin Transactions 2, 1981
Spectroscopy, 2003
Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of... more Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of solution 13 C NMR chemical shifts. NMR spectroscopic data and comparison with two anils model compound, namely, salicylideneaniline (1A) and naphthalylidinequinoline (2A) were used to represent the enol (A) and the keto (H) forms. The 13 C NMR chemical shifts data of the novel series 4A (compounds, 4-12) were used together with the values 13 C chemical shifts data of compounds 1A and 2A to calculate the % keto form. The calculated % keto form of 3A was compared to that calculated for series 4A compounds.
![Research paper thumbnail of Synthesis and properties of unsymmetrical azatrioxa[8]circulenes](https://attachments.academia-assets.com/46670870/thumbnails/1.jpg)
](Org. Biomol. Chem., 2015
Insights to the subtle reactivity patterns of hydroxy-substituted carbazoles allows the precise s... more Insights to the subtle reactivity patterns of hydroxy-substituted carbazoles allows the precise synthesis of unsymmetrical azatrioxa[8]circulenes by the reaction of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones in the presence of an oxidant (chloranil) and a Lewis acid (BF 3 OEt 2 ). The unique synthetic control obtained originates from the selectivity obtained upon reacting N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with an electron-rich benzoquinone to give first the C-C bond formation and then subsequently the dibenzofuran formation with high regioselectivity. Herein the first synthesis of unsymmetrical antiaromatic azatrioxa[8]circulenes and the full characterization using NMR spectroscopy, optical spectroscopy, electrochemistry, computational techniques and single crystal X-ray crystallography is reported. The controlled stepwise condensation of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones gives selectively the unsymmetrical azatrioxa[8]circulenes. † Electronic supplementary information (ESI) available: NMR spectra for new compounds, general experimental procedures, a detailed NMR assignment and further electrochemical assignments. CCDC 1032471. For ESI and crystallographic data in CIF or other electronic format see Scheme 1 Logic of diazadioxa[8]circulene (1) 15b and azatrioxa[8]circulene (2) 15a synthesis. Scheme 2 Pathway to unsymmetrical azatrioxa[8]circulene. R 2 of the first 1,4-benzoquinone must be an electron donating group, otherwise the diazadioxa[8]circulene is the main product. Fig. 1 Azatrioxa[8]circulenes (2) described in this paper.
Journal of the Chemical Society, Perkin Transactions 2, 1980
... and M. Tiecco, Gazzetta, 1967, 96, 1792. l6 K. F. Fieser and LM Joshel, J . Amer. Chem. Soc.,... more ... and M. Tiecco, Gazzetta, 1967, 96, 1792. l6 K. F. Fieser and LM Joshel, J . Amer. Chem. Soc., 1940, 62, l7 HV Ansell, P. J. Sheppard, C. F. Simpson, M. A. Stroud, F. Masetti, G. Batrocci, arid G. Galiazzo, Gazzetta, 1975,105, ...
Spectroscopy, 1997
The abundance 1 H-NMR spectra of some new mono-and diacetyl compounds derived from 2,2 -dimethyl-... more The abundance 1 H-NMR spectra of some new mono-and diacetyl compounds derived from 2,2 -dimethyl-, 3,3dimethyl-, and 4,4 -dimethylbiphenyls were recorded. Unambiguous signal assignment of the methyl groups of the aromatic biphenyl rings were made for the structure elucidation.
Physical chemistry chemical physics : PCCP, 2015
A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectrosc... more 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 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 piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.
RSC Adv., 2015
ABSTRACT Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurem... more 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.
Tetrahedron Letters, 2014
ABSTRACT It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)trieth... more 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.
The Journal of Physical Chemistry A, 2004
The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T an... more The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T and ∆S T , of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy. Polar solvents shift the equilibrium toward the quinone form (for the unsubstituted derivative 1c, K T ) 0.20 (cyclohexane) and K T ) 1.49 (ethanol)). Both donor (MeO, NMe 2 ) and acceptor (CN, NO 2 ) substituents lead to a decreased K T independent of solvent polarity. In apolar solvents, for all derivatives 1a-1e, the enol imine a enaminone equilibria are endergonic but exothermic. Linear solvation energy relationships allow extrapolation of ∆G T to the gas phase. Density functional theory calculations (B3LYP/6-311+G**) yield good agreement with these extrapolated ∆G T values. Solvent effects on 1c are also successfully reproduced by the calculations. Geometric (O‚‚‚N distance) and energetic criteria (conformer energy differences, homodesmotic reactions) establish the importance of intramolecular hydrogen bonding for the tautomerism of these compounds. The results obtained for 1a-1e are compared with tautomeric properties of the isomeric naphthaldehyde anils 2-4, the monocyclic analogues 5 and 6, the corresponding azo derivatives 7-9, and the N-alkyl derivative 10.
Tetrahedron, 1979
Ab&a&-Direct cyanation, using the heterogeneous Friedel-Crafts system cyanogen bromide/aluminium ... more Ab&a&-Direct cyanation, using the heterogeneous Friedel-Crafts system cyanogen bromide/aluminium chloride, has given good yields of the following carbonitriles: anthracene-9-,
Spectroscopy Letters, 1992
Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE F... more Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE Fadhil S. Kamounah Chemistry Department, College of Education, University of Sasrah, Basrah, Iraq Sawsan H. Shawkat and Salman R. Salman* ...
Journal of Labelled Compounds and Radiopharmaceuticals, 2011
ABSTRACT Acetylation of cedarwood oil (Virginia) leads besides acetyl cedrene also to a minor pro... more 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.
Phys Chem Chem Phys, 2003
ABSTRACT
Spectrosc Lett, 2002
Enol-Keto tautomerism in a new novel series of naphthylidi-neaniline Schiff bases were studied us... more Enol-Keto tautomerism in a new novel series of naphthylidi-neaniline 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) ...
Spectroscopy Letters, Aug 19, 2006
... Hansen PE, Duns F., Schmitt P. Org. Magn. Reson. 1982, 18,58. Page 8. 666 KAMOUNAH ANDSALMAN ... more ... Hansen PE, Duns F., Schmitt P. Org. Magn. Reson. 1982, 18,58. Page 8. 666 KAMOUNAH ANDSALMAN 12. Salman SR, Kanber SK, Arsalan KL Spectrosc. Letters 1991, 24(9), 1153. 13. Salman SR, Farrant RD, Lindon JC Spectrosc. Letters 1991, 24, 1071. 14. ...
The Journal of Physical Chemistry a, Sep 1, 2004
The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T an... more The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T and ∆S T , of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy. Polar solvents shift the equilibrium toward the quinone form (for the unsubstituted derivative 1c, K T ) 0.20 (cyclohexane) and K T ) 1.49 (ethanol)). Both donor (MeO, NMe 2 ) and acceptor (CN, NO 2 ) substituents lead to a decreased K T independent of solvent polarity. In apolar solvents, for all derivatives 1a-1e, the enol imine a enaminone equilibria are endergonic but exothermic. Linear solvation energy relationships allow extrapolation of ∆G T to the gas phase. Density functional theory calculations (B3LYP/6-311+G**) yield good agreement with these extrapolated ∆G T values. Solvent effects on 1c are also successfully reproduced by the calculations. Geometric (O‚‚‚N distance) and energetic criteria (conformer energy differences, homodesmotic reactions) establish the importance of intramolecular hydrogen bonding for the tautomerism of these compounds. The results obtained for 1a-1e are compared with tautomeric properties of the isomeric naphthaldehyde anils 2-4, the monocyclic analogues 5 and 6, the corresponding azo derivatives 7-9, and the N-alkyl derivative 10.
Spectrosc Lett, 1990
The O‒H…π interaction between proton donor systems phenol, substituted phenols, benzyl alcohol an... more The O‒H…π interaction between proton donor systems phenol, substituted phenols, benzyl alcohol and cyclohexanol and proton acceptor systems benzene, toluene, m- and p-xylenes, naphthalene and anthracene have been studied by infrared spectroscopy. It is found that the strength of the O‒H…π hydrogen bonding decreases in the following order: phenol > benzyl alcohol > cyclohexanol, and phenol > cresol> 2,6-dimethyl phenol > 2,4,6-tri-tret&utyl phenol. The strength of the proton acceptors, on the other hand, decreases in the fol lowing order: xylene > toluene > benzene > chlorobenzene, and for polyaromatic bases the trend is benzene > naphthalene > anthracene.
Bioconjugate Chemistry, Jun 16, 2010
Attachment of molecules and proteins to surfaces is of great interest for the development of a la... more 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.
Spectroscopy Letters, Sep 23, 2006
Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE F... more Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE Fadhil S. Kamounah Chemistry Department, College of Education, University of Sasrah, Basrah, Iraq Sawsan H. Shawkat and Salman R. Salman* ...
Journal of the Chemical Society, Perkin Transactions 2, 1981
Spectroscopy, 2003
Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of... more Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of solution 13 C NMR chemical shifts. NMR spectroscopic data and comparison with two anils model compound, namely, salicylideneaniline (1A) and naphthalylidinequinoline (2A) were used to represent the enol (A) and the keto (H) forms. The 13 C NMR chemical shifts data of the novel series 4A (compounds, 4-12) were used together with the values 13 C chemical shifts data of compounds 1A and 2A to calculate the % keto form. The calculated % keto form of 3A was compared to that calculated for series 4A compounds.
Org. Biomol. Chem., 2015
Insights to the subtle reactivity patterns of hydroxy-substituted carbazoles allows the precise s... more Insights to the subtle reactivity patterns of hydroxy-substituted carbazoles allows the precise synthesis of unsymmetrical azatrioxa[8]circulenes by the reaction of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones in the presence of an oxidant (chloranil) and a Lewis acid (BF 3 OEt 2 ). The unique synthetic control obtained originates from the selectivity obtained upon reacting N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with an electron-rich benzoquinone to give first the C-C bond formation and then subsequently the dibenzofuran formation with high regioselectivity. Herein the first synthesis of unsymmetrical antiaromatic azatrioxa[8]circulenes and the full characterization using NMR spectroscopy, optical spectroscopy, electrochemistry, computational techniques and single crystal X-ray crystallography is reported. The controlled stepwise condensation of N-benzyl-2,7-di-tert-butyl-3,6-dihydroxycarbazole with two different 1,4-benzoquinones gives selectively the unsymmetrical azatrioxa[8]circulenes. † Electronic supplementary information (ESI) available: NMR spectra for new compounds, general experimental procedures, a detailed NMR assignment and further electrochemical assignments. CCDC 1032471. For ESI and crystallographic data in CIF or other electronic format see Scheme 1 Logic of diazadioxa[8]circulene (1) 15b and azatrioxa[8]circulene (2) 15a synthesis. Scheme 2 Pathway to unsymmetrical azatrioxa[8]circulene. R 2 of the first 1,4-benzoquinone must be an electron donating group, otherwise the diazadioxa[8]circulene is the main product. Fig. 1 Azatrioxa[8]circulenes (2) described in this paper.
Journal of the Chemical Society, Perkin Transactions 2, 1980
... and M. Tiecco, Gazzetta, 1967, 96, 1792. l6 K. F. Fieser and LM Joshel, J . Amer. Chem. Soc.,... more ... and M. Tiecco, Gazzetta, 1967, 96, 1792. l6 K. F. Fieser and LM Joshel, J . Amer. Chem. Soc., 1940, 62, l7 HV Ansell, P. J. Sheppard, C. F. Simpson, M. A. Stroud, F. Masetti, G. Batrocci, arid G. Galiazzo, Gazzetta, 1975,105, ...
Spectroscopy, 1997
The abundance 1 H-NMR spectra of some new mono-and diacetyl compounds derived from 2,2 -dimethyl-... more The abundance 1 H-NMR spectra of some new mono-and diacetyl compounds derived from 2,2 -dimethyl-, 3,3dimethyl-, and 4,4 -dimethylbiphenyls were recorded. Unambiguous signal assignment of the methyl groups of the aromatic biphenyl rings were made for the structure elucidation.
Physical chemistry chemical physics : PCCP, 2015
A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectrosc... more 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 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 piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.
RSC Adv., 2015
ABSTRACT Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurem... more 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.
Tetrahedron Letters, 2014
ABSTRACT It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)trieth... more 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.
The Journal of Physical Chemistry A, 2004
The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T an... more The enol imine a enaminone tautomerization constants, K T , and thermodynamic parameters, ∆H T and ∆S T , of 1-hydroxy-2-naphthaldehyde Schiff bases are determined by UV/vis spectroscopy. Polar solvents shift the equilibrium toward the quinone form (for the unsubstituted derivative 1c, K T ) 0.20 (cyclohexane) and K T ) 1.49 (ethanol)). Both donor (MeO, NMe 2 ) and acceptor (CN, NO 2 ) substituents lead to a decreased K T independent of solvent polarity. In apolar solvents, for all derivatives 1a-1e, the enol imine a enaminone equilibria are endergonic but exothermic. Linear solvation energy relationships allow extrapolation of ∆G T to the gas phase. Density functional theory calculations (B3LYP/6-311+G**) yield good agreement with these extrapolated ∆G T values. Solvent effects on 1c are also successfully reproduced by the calculations. Geometric (O‚‚‚N distance) and energetic criteria (conformer energy differences, homodesmotic reactions) establish the importance of intramolecular hydrogen bonding for the tautomerism of these compounds. The results obtained for 1a-1e are compared with tautomeric properties of the isomeric naphthaldehyde anils 2-4, the monocyclic analogues 5 and 6, the corresponding azo derivatives 7-9, and the N-alkyl derivative 10.
Tetrahedron, 1979
Ab&a&-Direct cyanation, using the heterogeneous Friedel-Crafts system cyanogen bromide/aluminium ... more Ab&a&-Direct cyanation, using the heterogeneous Friedel-Crafts system cyanogen bromide/aluminium chloride, has given good yields of the following carbonitriles: anthracene-9-,
Spectroscopy Letters, 1992
Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE F... more Page 1. SPECTROSCOPY LETTERS, 25(4) 9 513-519 (1992) TBUTOMERISM IN SCIL LCYLIDENE PENZYLAM INE Fadhil S. Kamounah Chemistry Department, College of Education, University of Sasrah, Basrah, Iraq Sawsan H. Shawkat and Salman R. Salman* ...