SPECTROSCOPIC STUDIES OF KETO–ENOL EQUILIBRIA: PART 1. SOLVENT EFFECTS

1962 ◽  
Vol 40 (12) ◽  
pp. 2267-2271 ◽  
Author(s):  
A. S. N. Murthy ◽  
A. Balasubramanian ◽  
C. N. R. Rao ◽  
T. R. Kasturi
Keyword(s):  
Infrared Spectra ◽  
Solvent Effects ◽  
Ethyl Acetoacetate ◽  
Spectroscopic Studies ◽  
Ultraviolet Spectroscopy ◽  
Keto Form ◽  
Local Association ◽  
Characteristic Frequencies ◽  
Solvent Molecules

Solvent effects on the keto–enol equilibria of ethyl acetoacetate, acetylacetone, ethyl cyclopentanone-2-carboxylate, and methyl 4-methylcyclopentane-1-,2-dione-3,4,5-tricarboxylate have been studied by ultraviolet spectroscopy. The extent of enolization is mainly determined by the stabilization of the keto form by local association with polar or proton-donating solvent molecules, just as in the case of n → π* transitions and infrared stretching frequencies. Solvent effects on infrared spectra reveal useful information regarding the characteristic frequencies of the tautomers.

Infrared spectroscopic studies of solvent effects on the conformation of n-alkanes

1986 ◽  
Vol 64 (8) ◽  
pp. 1544-1547 ◽  
Author(s):  
H. L. Casal ◽  
P. W. Yang ◽  
H. H. Mantsch
Keyword(s):  
Chain Length ◽  
Infrared Spectra ◽  
Solvent Effects ◽  
Spectroscopic Studies ◽  
Thermodynamic Quantities ◽  
Branched Hydrocarbons ◽  
Infrared Spectroscopic ◽  
Induced Changes

The infrared spectra of specifically deuterated n-tridecane-7,7-d2 pure and mixed with several linear and branched hydrocarbons have been measured as a function of temperature. The average gauche fraction at the middle of the n-tridecane chain has been determined from the intensities of conformation-specific CD2 rocking bands. The results indicate that the concentration of gauche rotamers in the centre of the n-C13 chains varies with the solvent. For example, when n-tridecane is dissolved in other n-hydrocarbons the gauche concentration decreases when the chain length of the solvent is shorter than n-C13 and increases when the solvent chains are longer than n-C13. However, no simple, direct correlation is found between these solvent-induced changes in gauche concentration and measured thermodynamic quantities of mixing.

Infrared and Photoacoustic Spectroscopic Studies of a Silica-Immobilized β-Diketone

1982 ◽  
Vol 36 (4) ◽  
pp. 436-440 ◽  
Author(s):  
D. S. Kendall ◽  
D. E. Leyden ◽  
L. W. Burggraf ◽  
F. J. Pern
Keyword(s):  
Infrared Spectra ◽  
Spectroscopic Studies ◽  
Basic Solution ◽  
Keto Form ◽  
Photoacoustic Spectrum ◽  
Acidic Solutions ◽  
Hydrogen Bonded

Infrared and photoacoustic spectroscopies have in combination produced useful information about an immobilized β-diketone, formed by the reaction of acetylacetone with p-chloromethylphenyltrimethoxysilane previously immobilized on silica. Evidence confirming the synthesis of immobilized 3-benzyl-2,4-pentanedione is presented. Comparisons with 3-benzyl-2,4-pentanedione, a model for the surface bonded ligand, were valuable. The bound β-diketone is largely in the keto tautomer on the surface. The photoacoustic spectrum shows that the remainder is in the form of an intermolecular hydrogen-bonded enol. In basic solution the enolate ion and metal-enolate complexes can be formed. Infrared spectra show that the keto form can bind metals in acidic solutions.

Structural and spectroscopic studies of transition metal nitrite complexes. VIII. Crystal structures and spectra of three pentanuclear species with stoichiometry [Ni5(N-substituted ethane-1,2-diamine)4(OH)2(NO2)8]

1981 ◽  
Vol 34 (10) ◽  
pp. 2139 ◽  
Author(s):  
AJ Finney ◽  
MA Hitchman ◽  
CL Raston ◽  
GL Rowbottom ◽  
AH White
Keyword(s):  
Transition Metal ◽  
Crystal Structures ◽  
General Formula ◽  
Infrared Spectra ◽  
Spectroscopic Studies ◽  
Molecular Structures ◽  
Structural Variations ◽  
Crystal And Molecular Structures

The preparation of a series of novel compounds of general formula [Ni5L4(NO2)8(OH)2] formed by ethane-1,2-diamine or one of five N-substituted ethane-1,2-diamines (L) is described. The crystal and molecular structures of the ethane-1,2-diamine, N,N'-diethylethane-1,2-diamine and N,N-dimethylethane-1,2-diamine complexes are reported. Each compound contains a planar, pentameric arrangement of nickel(II) ions, linked by bridging hydroxide and nitrite ligands. The details of the nitrite bridges differ among the complexes, causing differences in their electronic and infrared spectra. The structural variations are probably caused by the differing steric requirements of the amine substituents.

Crystal structure, spectroscopic studies and theoretical studies of thiobarbituric acid derivatives: understanding the hydrogen-bonding patterns

2018 ◽  
Vol 74 (12) ◽  
pp. 1703-1714 ◽  
Author(s):  
Anamika Sharma ◽  
Sizwe J. Zamisa ◽  
Sikabwe Noki ◽  
Zainab Almarhoon ◽  
Ayman El-Faham ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Materials Science ◽  
Thiobarbituric Acid ◽  
Intramolecular Hydrogen Bonding ◽  
Spectroscopic Studies ◽  
Enol Form ◽  
Keto Form ◽  
X Ray Crystallography ◽  
Schiff Base Formation ◽  
Intramolecular Hydrogen

In addition to their wide-ranging applications in the pharmaceutical industry, thiobarbituric acid (TBA) derivatives are also known to possess applications in engineering and materials science. 20 TBA derivatives, with diversity at the N and C-5 positions through acylation, Schiff base formation, Knoevenagel condensation, thioamide and enamine formation, were studied. The absolute configurations for six derivatives, namely 5-acetyl-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C10H14N2O3S, A01, 1,3-diethyl-5-propionyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C11H16N2O3S, A02, tert-butyl [1-(1,3-diethyl-4,6-dioxo-2-thioxohexahydropyrimidin-5-yl)-3-methyl-1-oxobutan-2-yl]carbamate, C18H29N3O5S, A06, 1,3-diethyl-4,6-dioxo-2-thioxo-N-(p-tolyl)hexahydropyrimidine-5-carbothioamide, C16H19N3O2S2, A13, 5-(1-aminoethylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C10H15N3O2S, A17, and 5-(1-aminopropylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C11H17N3O2S, A18, were confirmed by single-crystal X-ray crystallography, which indicates the formation of intramolecular hydrogen bonding in all six cases and intermolecular hydrogen bonding for A17. In A13, the presence of two intramolecular hydrogen bonds was observed. The stabilization of the enol form over the keto form was confirmed by computation. In order to convert the keto form to the enol form, an energy barrier of 55.05 kcal mol−1 needs to be overcome, as confirmed by transition-state calculations.

Spectroscopic Studies with N-Chloroarylsulphonamides: IR and 1H, 13C and 23Na Nmr Spectra of Sodium Salts of N-Chloro-Mono- and Di-Substituted-Benzenesulphonamides, 4-X-C6H4SO2NANCl (X = H; CH3; C2H5; F; Cl; Br; I or NO2) and i-X, j-YC6H3SO2NANCl (i-X, j-Y = 2,3-(CH3)2; 2,4-(CH3)2; 2,5-(CH3)2; 2-CH3, 4-Cl; 2-CH3, 5-Cl; 3-CH3, 4-Cl; 2,4-Cl2 or 3,4-Cl2)

2003 ◽  
Vol 58 (1) ◽  
pp. 51-56 ◽  
Author(s):  
◽  
J. D. D’Souza ◽  
B. H. Arun Kumar
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Infrared Spectra ◽  
Phenyl Ring ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spectroscopic Studies ◽  
Sodium Salts ◽  
Experimental Chemical Shift ◽  
23Na Nmr

In an effort to introduce N-chloroarylsulphonamides of different oxydising strengths, sixteen sodium salts of N-chloro-mono- and di-substituted benzenesulphonamides of the configuration, 4- X-C6H4SO2NaNCl (where X = H; CH3; C2H5; F; Cl; Br; I or NO2) and i-X, j-YC6H3SO2NaNCl (where i-X, j-Y = 2,3-(CH3)2; 2,4-(CH3)2; 2,5-(CH3)2; 2-CH3,4-Cl; 2-CH3,5-Cl; 3-CH3,4-Cl; 2,4- Cl2 or 3,4-Cl2) are prepared, characterized through their infrared spectra in the solid state and NMR spectra in solution. The υN-Cl frequencies vary in the range 950 - 927 cm−1. Effects of substitution in the benzene ring in terms of electron donating and electron withdrawing groups have been considered, and conclusions drawn. The chemical shifts of aromatic protons and carbon-13 in all the N-chloroarylsulphonamides have been calculated by adding substituent contributions to the shift of benzene. Considering the approximation employed the agreement between the calculated and experimental chemical shift values for different protons or carbon-13 is quite good. Effects of phenyl ring substitution on chemical shift values of both 1H and 13C are also graphically represented in terms of line diagrams.

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