Tautomerization tendencies of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and cyclic β-keto esters of five- and six-membered rings

2001 ◽  
Vol 79 (4) ◽  
pp. 448-454 ◽  
Author(s):  
Antonio Rojas ◽  
Alfonso Perez-Encabo ◽  
Ignacio Herraiz-Sierra ◽  
Carlos A Blanco

NMR and kinetics studies of the tautomeric equilibrium of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and methyl 2-oxocycloalkanecarboxylates of five- and six-membered rings have been carried out. By comparing 1H NMR and 13C NMR spectra recorded in D2O–DOCD3 and CDCl3, with those results derived using a bromination kinetic procedure in dilute aqueous solution, information concerning tautomeric interconversion is provided. Some discussions considering ionisation equilibria and rate constants involved have also been considered. Solvent and concentration effects on keto-enol equilibria have also been discussed.Key words: 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, methyl 2-oxocycloalkanecarboxylates, equilibrium, tautomerization, ionization.

2004 ◽  
Vol 59 (6) ◽  
pp. 716-720 ◽  
Author(s):  
Frank Biesemeier ◽  
Klaus Harms ◽  
Ulrich Müller

1,4-Bis(p-pentazolylphenyl)butane (1), 1-p-azidophenyl-4-p-pentazolylphenyl-butane (2) and 1,4-bis(p-azidophenyl)butane (3) were obtained by the reaction of 1,4-diphenylbutane-4’,4”- bis(diazonium) ions with sodium azide in methanol at −50 °C. In the 1H and 13C NMR spectra the three compounds can be distinguished unequivocally. At −50 °C a mixture with a composition 1:2:3 of 10:30:60 was obtained. By recrystallization first from dichloromethane/methanol and then from dichloromethane/petroleum ether the pentazole components were enriched to a composition ratio of 21:62:17. The rate constants of the decompositions 1→2 and 2→3 at 0 °C were determined from the variation of the 1H NMR intensities. At room temperature all of the material is converted to 3. 3 crystallizes in two monoclinic modifications. At −70 °C a modification 3-LT having space group P21/c (a = 950.8, b = 1192.6, c = 701.3 pm, β = 92.55°, Z = 2; R = 0.075) was obtained. The modification crystallizing at room temperature (3-HT) has space group I2/a (a = 1514.5, b = 498.1, c = 2027.9 pm, β = 92.73°, Z = 4; R = 0.040). Whereas both modifications consist of nearly identical molecules, their packings are quite different. When the low temperature modification is warmed to room temperature, its crystals jump like flees and are disrupted to a fine powder.


1981 ◽  
Vol 46 (8) ◽  
pp. 1913-1929 ◽  
Author(s):  
Bohdan Schneider ◽  
Pavel Sedláček ◽  
Jan Štokr ◽  
Danica Doskočilová ◽  
Jan Lövy

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.


1995 ◽  
Vol 60 (4) ◽  
pp. 619-635 ◽  
Author(s):  
Václav Křeček ◽  
Stanislav Hilgard ◽  
Miloš Buděšínský ◽  
Alois Vystrčil

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1H NMR, 13C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1H and 13C NMR spectra are discussed.


2020 ◽  
Author(s):  
Abdulbasit Haliru Yakubu ◽  
Iliya Ibrahim ◽  
Abdulqadir bukar bababe ◽  
Hassan Yesufu ◽  
mohammed Garba Tom

<p><i>Cyphostemma adenocaule </i>(Steud. ex A. Rich.) is one of the specie plant that belongs to the family vitacea. In this study, Trilinolein was isolated and characterized from the methanol root extract of the plant. Column chromatography over silica gel granules as the stationary phase and eluted with a mobile phase mixture of n-Hex-EtA; EtA-CHCL3 and CHCL<sub>3</sub>-MeOH with gradient increasing polarity, followed by a second column using saphadex-LH20 and 100% MeOH as stationary and mobile phase vehicle respectively. TLC was developed with EtA 15: CHCL3<sub> </sub>8: MeOH 4: H<sub>2</sub>O 1 as solvent system; sprayed with 10% H<sub>2</sub>SO<sub>4 </sub>,Vanillin-sulphuric acid, and/ or Polyethylene glycol PEG and heat for spot detection and confirmation of bioactive principles. Compound CA1 was obtained and purified with CHCL3 to give a yellow semi-solid compound (0.23g). The <sup>1</sup>H-NMR spectra showed 9 different signals; a signal peak of a glycerol (-C<b>H<sub>2</sub></b>OCOR-) moiety on the first α-C chain and on the third αʹ-C at 4.143-4.187ppm and 4.296-4.325ppm respectively, while that of a β glycerol (-C<b>H</b>COR-) at 5.286ppm. Signals of an allylic methylene group at 2.023-2.035ppm, Olefenic hydrogen group at signal peak of 5.362ppm and a diallylic methylene group at signal 2.790ppm were also observed. In the <sup>13</sup>C NMR spectra of compound CA1, 57 carbon atoms where observed, multiple signals overlapping at a range of 14.13-34.21ppm corresponding to the aliphatic CH3 (<b>C18</b>), CH2 (<b>C2, C3, C4, C5, C6, C7, C15, C16, and C17</b>) and allylic (<b>C8, C14</b>) carbon atoms. Signals at 127.90-130.24ppm were assigned to the olefienic C atoms (<b>C9, C10, C12</b>, and <b>C13</b>) while signal of 172.87ppm and 173.32ppm were assigned to the carbonyl (<b>C</b>=O) carbon atoms (<b>C1 </b>and<b> C2</b>) respectively (Table 2). </p> <p>Analysis with DEPT-135, H-H COSY, HMBC and HSQC assignments of CA1 augments assignment of signals made for CA1 from <sup>1</sup>H-NMR and <sup>13</sup>C-NMR and corresponded to that of Trilinolein <u>(<a href="https://pubchem.ncbi.nlm.nih.gov/#query=C57H98O6">C<sub>57</sub>H<sub>98</sub>O<sub>6</sub></a>, </u>MW 879.4 g/mol). The isolated compound was positive for the acrolein test for triglycerides; fat & oil and had an IC<sub>50</sub> of 46.08µg/ml radical scavenging activity.</p>


2018 ◽  
Vol 14 ◽  
pp. 3011-3017
Author(s):  
Akın Sağırlı ◽  
Yaşar Dürüst
Keyword(s):  
2D Nmr ◽  
X Ray ◽  
H Nmr ◽  
Tof Ms ◽  

The present work describes an unfamiliar reaction of 5-(chloromethyl)-3-substituted-phenyl-1,2,4-oxadiazoles with KCN affording trisubstituted 1,2,4-oxadiazol-5-ylacetonitriles and their parent alkanes, namely, 1,2,3-trisubstituted-1,2,4-oxadiazol-5-ylpropanes. To the best of our knowledge, the current synthetic route leading to decyanated products will be the first in terms of a decyanation process which allows the transformation of trisubstituted acetonitriles into alkanes by the incorporation of KCN with the association of in situ-formed HCN and most likely through the extrusion of cyanogen which could not be detected or isolated. In addition, the plausible mechanisms were proposed for both transformations. The structures of the title compounds were identified by means of IR, 1H NMR, 13C NMR, 2D NMR spectra, TOF–MS and X-ray measurements.


2007 ◽  
Vol 62 (3) ◽  
pp. 397-406 ◽  
Author(s):  
Stephan W. Kohl ◽  
Katharina Kuse ◽  
Markus Hummert ◽  
Herbert Schumann ◽  
Clemens Mügge ◽  
...  

Two improved routes to synthesize 1-benzyl-1,4,7,10-tetraazacyclododecane (6) and 1,4,7,10- tetraazacyclododecane-1-acetic acid ethyl ester (11) are described as well as the synthesis of 1-{2-[4-(maleimido-N-propylacetamidobutyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane- 4,7,10-triacetic acid (17) and its Y, Ho, Tm, and Lu complexes. The 1H and 13C NMR spectra of the new compounds as well as the single crystal X-ray structure analyses of the intermediates 4-benzyl-1,7-bis(p-toluenesulfonyl)diethylenetriamine (3) and 1,4,7-tris(p-toluenesulfonyl)diethylenetriamine (7) are reported and discussed. The rare earth complexes of 17 have been characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry.


1986 ◽  
Vol 64 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Daniel Cozak ◽  
François Gauvin ◽  
Jacques Demers

The paramagnetic 1H nmr spectra for manganocene (1) and 1.1′-dimethylmanganocene (2), and the 13C nmr spectra for 1,1′-diethylmanganocene (3) have been recorded in toluene solvent over a −90 to 90 °C temperature range. 1 shows a low field and a high field ring proton resonance in its spectrum near −59 °C. At higher temperatures the low field resonance is prevalent and becomes gradually averaged due to a fast spin exchange process that dominates the spectrum at 90 °C. For the ring substituted derivatives 2 and 3, resonances due to only one paramagnetic species were detected in the low temperature range. Above ambient temperature a new spectrum due to rapid spin exchange averaging is observed for these complexes. Results are readily interpreted in terms of ground state molecular cross-over exchanges between the 2E2g, 6A1g, and 2A1g spin states of the complexes.


1975 ◽  
Vol 30 (9-10) ◽  
pp. 788-793 ◽  
Author(s):  
Ludger Ernst

During a reinvestigation of the 13C NMR spectra of 1-fluoronaphthalene (1) and of 2-fluoronaphthalene (2) at 20 and 25.16 MHz, uncertainties that existed in the literature about signal assignments for 1 could be cleared. In the spectral analyses for 2 given so far, five out of ten signals were incorrectly assigned. The corrected assignment is supported by extensive 13C{1H} double resonance experiments, by recording of proton-coupled 13C and 13C{19F} spectra and by off-resonance 13C{1H} noise-decoupling. The results show a strong + M-effect of the fluorine substituents on 13C chemical shifts similar to the effects of OH and OCH3 groups. 1H NMR spectra of 1 and 2 could be partially assigned by decoupling of the 19F resonances and by iterative analysis.


1981 ◽  
Vol 36 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Helmut Burdorf ◽  
Christoph Eischenbroich

Abstract The thioanisole-π-complexes (methylthio-η-benzene)-(η-benzene)-chromium (2) and bis(methylthio-η-benzene)chromium (3) have been prepared via lithiation of bis(η-benzene)-chromium and consecutive reaction with dimethyldisulfide. 1H NMR and 13C NMR spectra of 2 and 3 as well as ESR-spectra of the corresponding radical cations 2.+ and 3.+ were recorded and analyzed. In contrast to C(η-arene)-Si and C(η-arene)-P bonds, C(y-arene)-S bonds are stable to solvolysis. With (norbornadiene)tetracarbonylmolybdenum, 3 readily forms [bis(methylthio-η-benzene)chromium]tetracarbonylmolybdenum (6) wherein 3 functions as a chelating ligand. 1H and 13C NMR evidence suggests, that at room temperature 6 undergoes rapid conformational interconversions.


RSC Advances ◽  
2014 ◽  
Vol 4 (85) ◽  
pp. 45433-45441 ◽  
Author(s):  
K. Sethuraman ◽  
P. Prabunathan ◽  
M. Alagar

In the present study three structurally different diamines namely bisphenol-A based ether diamine, octane diol based ether diamine, and capron based diamine were synthesized and characterized using FT-IR, 1H-NMR and 13C-NMR spectra.


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