Strukturbestimmungen von ungesättigten Ketonen mit Hilfe von Infrarot‐ und Ultraviolett‐Spektren

Mecke, R.; Noack, K.

doi:10.1002/cber.19600930132

Cited by 95 publications

(10 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Siiiiilar effects in tlie ultraviolet spectra of conjugated carbonyl compounds and certain differences in the infrared and Raman spectra of coinpounds of kno\vn geometry (7)(8)(9)(10)(11)(12) have been suggested to distinguish between tlie two planar cornforiiiations. Tlie general characteristics of the two forms are sumiilarized iii Table VIII.…”

Section: Steric I~zlzibition Of Conjugationmentioning

confidence: 99%

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

Marr¹,

Stothers²

1965

Can. J. Chem.

View full text Add to dashboard Cite

The 15.1 Mc/s I3C n.1n.r. spectra of 34 a,p-unsat~~rated carbonyl compounds have been obtained and the chemical shifts of the olefnic and carbonyl carbon nuclei are reported. Esamples were drawn from the acyclic and five-and six-membered ring alicyclic series. A few aldehydes are included although most of the con~pounds are ketones. In the case of compounds ass~~rned to be planar, variations of the olefinic shieldings with alkyl substitution parallel those observed previously for olefinic hydrocarbons. The key factor governing the chemical shifts of the carbo~lyl-carbon nuclei appears to be the extent of conjugation in a given system. Conseq~~ently, the 13C results prov~de evidence for steric interference to coplanarity in the hi~ldered systems. This approach is compared with other methods of estimating the extent of steric inhibition of co~ljugation and its merits are assessed.

show abstract

Section: Steric I~zlzibition Of Conjugationmentioning

confidence: 99%

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

Marr¹,

Stothers²

1965

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…We assume that the rotation defined by Â 3 is too strongly hindered, 27 and optimize the geometry with no constraints on this dihedral angle.…”

Section: Ab Initio Calculationsmentioning

confidence: 99%

Application of the model‐free approach to low molecular weight systems with hindered internal rotation: cinnamoylmesitylene

Denkova

Dimitrov

Bakalova

et al. 2003

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

We investigated the molecular dynamics of the molecule of cinnamoylmesitylene, a substituted chalcone. Known rotation barriers for the O C-4 -C-3 C-2 bond of substituted chalcones are in the range of values accessible to modern NMR techniques. The internal rotation about the C-3 -C-4 bond is found to be fast relative to the complete lineshape analysis (CLSA) time-scale. To determine the activation parameters of overall and internal motions of the molecule, the Lipari-Szabo model-free analysis of the relaxation times and heteronuclear NOE data was used instead. Simultaneous analysis of both heteronuclear spin-lattice relaxation times and NOE data for the two carbon atoms C-2 and C-7 in the O C-4 -C-3 C-2 and mesitylene fragments at different temperatures was performed. The correlation times and activation energies of overall and internal motions and the generalized order parameter, which are measures of the molecular mobility, were thus determined. The standard enthalpies of activation, 1H 6 = , calculated from the experimental data for C-2 and C-7, are 5.6 and 6.6 kcal mol −1 , respectively. Theoretical estimates of the barriers to internal rotations by ab initio MO calculations were made to verify the experimental results. The agreement between the NMR and theoretical results was good.

show abstract

“…The preparation and purification of the ketones have been described by IIIeclte and Koacli (2). The infrared spectra were measured on Perkin-Elmer A/Iodel 21 and NIodel 112 spectronleters using the low-temperature technique described previously (6).…”

Section: Esperiaienti-\l Meti-iods a N D R E S U L T Smentioning

confidence: 99%

“…The s-cis (I) and s-trans (11) conformations of open-chain a,p-unsaturated ketones can be distinguished from the positions and intensities of the C=O and C=C stretching bands in the infrared (1)(2)(3)(4) and Ranla11 (5) spectra. In the liquid state most conjugated ketones exist predorni~la~ltly or perhaps exclusively in one or other of the two conformations, but NIecke and Noacli (2) have observed that the infrared spectrum of tratzs-A3-penten-2-one (IIIa) and related colnpoullds (IIIb-IIId) exhibit two carbony1 bands near 1700 cm-I and 1680 cm-I in tetracl~loroetl~yle~~e solution.…”

Section: Introductionmentioning

confidence: 99%

“…In the liquid state most conjugated ketones exist predorni~la~ltly or perhaps exclusively in one or other of the two conformations, but NIecke and Noacli (2) have observed that the infrared spectrum of tratzs-A3-penten-2-one (IIIa) and related colnpoullds (IIIb-IIId) exhibit two carbony1 bands near 1700 cm-I and 1680 cm-I in tetracl~loroetl~yle~~e solution. The positions of these bands suggested an equilibriu~n between the s-cis and s-trans isomers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

CONFORMATIONAL EQUILIBRIA IN OPEN-CHAIN Α,β-Unsaturated KETONES

Noack¹,

Jones²

1961

Can. J. Chem.

View full text Add to dashboard Cite

The infrared and Raman spectra of trans-43-penten-2-one have beer1 ~neasured over the temperature range +30° to -75' and +8j0 to 4-5' respectively. The temperat~~re-dependent changes observed in the spectra indicate that this Icetone exists as an equilibrii~rll mixture of s-cis and s-trans conformational isorners in the liquid state. 'The s-trans forrn is the Inore stable and is present exclusively in the crystalline solid.Silllilar measurements have been carried out on A3-buten-Zone. The infrared and Raman spectra of this Icetone also exhibit temperature effects that can be explained by a similar equilibrium, though the evidence is not as conclusive as for tralcs-43-penten-2-one.The influence of allcyl substitution a t the ol-and 8-carborl atoms OII the relative stability of the s-cis and s-trans forms of a,8-u1lsaturated ketones is discussed. INTRODUCTIONThe s-cis (I) and s-trans (11) conformations of open-chain a,p-unsaturated ketones can be distinguished from the positions and intensities of the C=O and C=C stretching bands in the infrared (1-4) and Ranla11 (5) spectra. In the liquid state most conjugated ketones exist predorni~la~ltly or perhaps exclusively in one or other of the two conformations, but NIecke and Noacli (2) have observed that the infrared spectrum of tratzs-A3-penten-2-one (IIIa) and related colnpoullds (IIIb-IIId) exhibit two carbony1 bands near 1700 cm-I and 1680 cm-I in tetracl~loroetl~yle~~e solution. The positions of these bandssuggested an equilibriu~n between the s-cis and s-trans isomers. Si~nilar doublet carbonyl bands were noted by Mecke and Noack for ketones of structure IVa-IVb. T i~n~n o l l s and collaborators (4) have co~ll~llented si~nilarly on the spectrunl of trans-kR-penten-2-one, and other exanlples of this behavior have been cited by Erslcine and Waight (3).111 the present investigation the effects of temperature on the infrared and Ramall spectra of trans-A3-penten-2-one and A3-buten-2-one have been exaini~led in a n attempt to confirm the existence of these equilibrium systems.'Manuscript

show abstract

Strukturbestimmungen von ungesättigten Ketonen mit Hilfe von Infrarot‐ und Ultraviolett‐Spektren

Cited by 95 publications

References 19 publications

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

Application of the model‐free approach to low molecular weight systems with hindered internal rotation: cinnamoylmesitylene

CONFORMATIONAL EQUILIBRIA IN OPEN-CHAIN Α,β-Unsaturated KETONES

Contact Info

Product

Resources

About

Strukturbestimmungen von ungesättigten Ketonen mit Hilfe von Infrarot‐ und Ultraviolett‐Spektren

Cited by 95 publications

References 19 publications

13C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

13C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

Application of the model‐free approach to low molecular weight systems with hindered internal rotation: cinnamoylmesitylene

CONFORMATIONAL EQUILIBRIA IN OPEN-CHAIN Α,β-Unsaturated KETONES

Contact Info

Product

Resources

About

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS

¹³C N.M.R. STUDIES: PART VI. CARBON-13 SPECTRA OF α,β-UNSATURATED CARBONYL COMPOUNDS