Structure and vibrational assignment of the enol form of 1,1,1-trifluoro-2,4-pentanedione

Zahedi-Tabrizi, Mansoureh; Tayyari, Fariba; Moosavi-Tekyeh, Zainab; Jalali, Alireza; Tayyari, Sayyed Faramarz

doi:10.1016/j.saa.2005.11.019

Cited by 59 publications

(45 citation statements)

References 31 publications

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“…Hence, it is reasonable to expect four C-H bands, corresponding to CH (EE), CH (EZ), CH (EE), and CH (EZ) vibrations. In 1,1,1-tri�uoro-2,4-pentanedione [11], which is exclusively in (ZZ) con�guration due to intramolecular H-bonding, the ole�nic CH stretching mode occurs at 3120 cm −1 . Similarly, in cis-1,2-di�uoroethylene the (C-H) wavenumber is 3133 cm −1 [4], therefore we ascribed the bands at 3134 and 3099 cm −1 to (C-H ) mode.…”

Section: Resultsmentioning

confidence: 99%

“…e pro�le of a very intensive (C=C) band ( Figure 1) ex facte creates an impression of single band, but thorough analysis showed [8] that there are two overlapped bands at 1588 and 1593 cm −1 (DMTBN), which we attributed to the (EZ) and (EE) conformers, respectively. It is worthy to note that in highly conjugated systems -C=C-C=O (C=O) and (C=C) vibrations are strongly coupled, possessing, in large measure, the character of out-of-phase and in-phase vibrational modes, respectively [10,11,[15][16][17]. Nevertheless, we shall continue to use the (C=O) and (C=C) as a convenient form of shorthand.…”

Section: Int(c-h ) (Ez)mentioning

confidence: 99%

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C–H⋯F Hydrogen Bond and Integral Intensities of Vinyl C–H Vibtations in Push-Pull β-Dimethylaminotrifluoromethyl Ketone and Its Deuterated Analog

et al. 2013

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The accurate analysis of infrared spectra (both wavenumbers and intensities) of (E)-4-(dimethylamino)-1,1,1-trifluorobut-3-en-2-one (DMTBN) and (E)-4-(hexadeutero-dimethylamino)-1,1,1-trifluorobut-3-en-2-one (d6-DMTBN) revealed that besides intramolecular hydrogen bond in the (EE) conformer, these enaminoketones form cyclic dimers between the (EZ) and (EE) conformers due to intermolecular hydrogen bonds, namely, O=C and . Evaluation of constant and enthalpy of formation of these H-bonds revealed that O=C bond has greater and more negative than bond (cf. 214.4 M−1, −21.7 kJ M−1dm3, and 16.4 M−1, −6.7 kJ M−1dm3, resp.). Consequently, stronger H-bond ⋯O=C is formed in the first place, whereas weaker H-bond is formed afterward. Moreover, formation of intermolecular hydrogen bond has influence on C–F vibrations, but analysis of this influence must take into account the fact that these vibrations in some cases are coupled with . True enthalpy of the equilibrium (EZ)⇌(EE) is positive (25.3 kJ M−1dm3), thus confirming results of DFT calculations, according to which the (EZ) conformer is more stable than the (EE) one.

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Section: Resultsmentioning

confidence: 99%

Section: Int(c-h ) (Ez)mentioning

confidence: 99%

C–H⋯F Hydrogen Bond and Integral Intensities of Vinyl C–H Vibtations in Push-Pull β-Dimethylaminotrifluoromethyl Ketone and Its Deuterated Analog

et al. 2013

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“…So the intramolecular hydrogen bond strength (IHBs) of these molecules are affected by varying in the bond lengths of chelated ring. The EWG tend to reduce IHB strength by two manners, the first conjugation with the enol double bond and the second by increasing positive charges on the carbonyl oxygen atom [10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

Correlation Between Parameters Related to Intramolecular Hydrogen Bond Strength and Hammett Constant in Para Substituted Benzoylacetone (A Theoretical and Experimental Study)

Darugar¹,

Vakili²,

Tayyari³

et al. 2017

Orient. J. Chem

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Conformational stability, equilibrium constant between two stable cis-enol forms, and intramolecular hydrogen bonding (IHB) of benzoylacetone (BA) and p-substituted benzoylacetone (X-BA), where X=NO 2 , OCH 3 , CH 3 , OH, CF 3 , Cl, F, and NH 2 , have been investigated by means of density functional theory (DFT) calculations and compared with the reported experimental results. According to our calculations, the energy difference between the two stable chelated enol forms is negligible, about 0.35-1.1 kcal/mol ranges in the gas phase and different solvents. The electronic effects of p-substituted benzoylacetone on IHB strength were determined and established by NMR, IR spectra, geometry, and topological parameters with Hammett linear free energy relationships. Also, the linear correlation coefficients between σ p and selected parameters related to IHB strength, such as geometrical, topological parameters, IR and NMR spectroscopic data, and NBO results related to IHBs were considered. Good linear correlations between σ p and the mentioned parameters were obtained

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“…Em IV, como em outras técnicas comparativas, é necessário obter o espectro para o padrão de cada isômero constitucional e assim estabelecer padrões para futuras comparações. 1 A técnica de RMN é muito eficaz na diferenciação de isômeros e a única capaz de realizar atribuições absolutas. A RMN usa, para estas atribuições, medidas de constantes de acoplamento e técnicas que identificam posicionamento bi e tridimensional de átomos ou grupo de átomos.…”

Section: Introductionunclassified

Atribuição absoluta e geral de isômeros constitucionais por espectrometria de massas: o caso das metilpiperidinas

Eberlin¹,

Benassi²

2012

Quím. Nova

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Recebido em 7/10/10; aceito em 20/5/11; publicado na web em 22/7/11 ABSOLUTE AND GENERAL ASSIGNMENT OF CONSTITUTIONAL ISOMERS BY MASS SPECTROMETRY: THE CASE OF METHYLPIPERIDINES. An absolute method is described via mass spectrometry (MS) for the structural assignment of isomers within the class of methylpiperidines. The method explores both the unimolecular and bimolecular gas phase behavior of structurally diagnostic fragment ions (SDFI). For the methylpiperidnes, the isomeric 2-methyl, 3-methyl and 4-methyl 2-azabutadienyl cations are found to function as SDFI. These fragment ions are expected to be formed from all members within the class, to be stable and to retain the structural information of the precursor molecule, and to not interconvert into one another. To characterize these SDFI, both the collision induced dissociation (CID) in argon and bimolecular ion/molecule chemistry with ethyl vinyl ether were compared.Keywords: mass spectrometry; diagnostic ions; methylpiperidines. INTRODUÇÃOA diferenciação de isômeros constitucionais, particularmente os que apresentam estruturas bastante similares, tais como as dos isômeros cis-trans ou orto/meta/para, tem representado um grande desafio químico e requerido o uso de diferentes técnicas analíticas. Isômeros são normalmente diferenciados por espectroscopia na região do infravermelho (IV), ressonância magnética nuclear (RMN) ou espectrometria de massas (MS, mass spectrometry). A técnica de IV permite atribuir grupos funcionais presentes na amostra, mas frequentemente não é capaz de caracterizar um isômero de forma absoluta (não comparativa). Em IV, como em outras técnicas comparativas, é necessário obter o espectro para o padrão de cada isômero constitucional e assim estabelecer padrões para futuras comparações. 1 A técnica de RMN é muito eficaz na diferenciação de isômeros e a única capaz de realizar atribuições absolutas. A RMN usa, para estas atribuições, medidas de constantes de acoplamento e técnicas que identificam posicionamento bi e tridimensional de átomos ou grupo de átomos. A sensibilidade de RMN é, porém, um limitante especialmente em análise de misturas e quando acoplada a técnicas de separação.Isômeros constitucionais podem apresentar diversas propriedades físico-químicas distintas, porém a massa molecular é a mesma. Como a MS se fundamenta principalmente na medida da massa (m/z) de moléculas isoladas na fase gasosa, tem apresentado em muitos casos fortes limitações quando a tarefa é distinguir isômeros. Para uma única nova molécula, para a qual espectros de massas de referência não estão disponíveis, a MS é incapaz de realizar atribuições absolutas de configuração.Diferentes estratégias baseadas na correlação entre estrutura e propriedades físico-químicas têm procurado suprir esta deficiência inerente da MS. Destacam-se as estratégias que exploram a diferença de reatividade unimolecular 2-4 ou bimolecular 5-7 de formas ionizadas de um determinado conjunto de moléculas isômeras. Estas técnicas não são, porém, absolutas pois é necessário comparar espe...

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Structure and vibrational assignment of the enol form of 1,1,1-trifluoro-2,4-pentanedione

Cited by 59 publications

References 31 publications

C–H⋯F Hydrogen Bond and Integral Intensities of Vinyl C–H Vibtations in Push-Pull β-Dimethylaminotrifluoromethyl Ketone and Its Deuterated Analog

C–H⋯F Hydrogen Bond and Integral Intensities of Vinyl C–H Vibtations in Push-Pull β-Dimethylaminotrifluoromethyl Ketone and Its Deuterated Analog

Correlation Between Parameters Related to Intramolecular Hydrogen Bond Strength and Hammett Constant in Para Substituted Benzoylacetone (A Theoretical and Experimental Study)

Atribuição absoluta e geral de isômeros constitucionais por espectrometria de massas: o caso das metilpiperidinas

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