Fluoroalcohols—XXI. Infrared, matrix infrared and Raman spectra of 1,1,1-trifluoro-2-propanol and its three deuterated analogues

Murto, Juhani; Kivinen, Antti; Edelmann, Kari; Hassinen, E.

doi:10.1016/0584-8539(75)80039-0

Cited by 32 publications

(13 citation statements)

References 17 publications

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“…Communications aCH stretch of the alkoxide occurs at afrequency more than 500 cm À1 lower than the a-CH stretch of the neutral alcohol. [10] While IR excitation of unfluorinated alkoxides leads to expulsion of H 2 to produce the corresponding enolate anion, fluorinated alkoxides,b yc ontrast, dissociate to give CF 3 À , except for 3 and 3-d 2 which give CF 3 CF 2 À and HF (or DF) loss. Forp rimary alkoxides the presence of two a-hydrogens implies ap air of low-frequencyC Hs tretches.I nt he case of 2,2,3,3,3-pentafluoro-n-propoxide (3,illustrated in panel Cof Figure 1) and 2,2,2-trifluoroethoxide (4,illustrated in panel D of Figure 1) the two bands are resolved and have widths comparable to the absorption profiles of the secondary alkoxides (for each of which as ingle band appears in this domain).…”

Section: Angewandte Chemiementioning

confidence: 99%

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Berden

Morton

2016

Angew Chem Int Ed

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CH stretches in hydrocarbon cations often shift to lower frequencies relative to neutral molecules, because they do not have sufficient electrons to give every bond an electron pair. A parallel effect in negatively charged species has not been previously observed. Here we show that CH bond weakening occurs in alkoxide anions as a consequence of hyperconjugation. The reasoning differs somewhat from the case of positively charged ions, but the net effect is the same: to lower CH stretching frequencies by hundreds of wavenumbers.

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Section: Angewandte Chemiementioning

confidence: 99%

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Berden

Morton

2016

Angew Chem Int Ed

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“…In particular it has been reported that the two CD stretching bands of CH3CDOHCH3, corresponding to the two conformers, are separated by 73 cm-1,9 but this frequency separation falls to less than half this value in CF3CDOHCF335 and CH3CDOHCF3. 36 If aldehydes possess low CH stretching frequencies due to "trans" lone pair interactions via the double bond, it might be anticipated that similar perturbed CH stretching frequencies would occur in systems containing the CH2=N group. In Table I are listed the CH2= and CH= stretching frequencies of a number of representative compounds of this kind.…”

Section: Data and Interpretationmentioning

confidence: 99%

Infrared frequency effects of lone pair interactions with antibonding orbitals on adjacent atoms

Bellamy¹,

Mayo²

1976

J. Phys. Chem.

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makes it possible to obtain a spectrum which reflects the effective symmetry E' of this ion at its lattice site. The site symmetry S of the NH4+ in the undeuterated crystal may be deduced from E', within the restrictions imposed by theory (Table I).This method and the analysis presented in this paper are capable of natural extension to the PH4+ and BH4~ions and in principle to any tetrahedral species XY4 in crystalline compounds. References and Notes(1) NRCCNo. 15064.(2) Postdoctoral Research Associate with Richard C. Lord, 1960-1962. (3) Our designation of vibrational modes follows that of G.

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“…14,18 Besides, the Raman and infrared spectra of HFP and HFP-d 2 have been previously characterized. 14,26 To calculate the isotope effect, nuclear shielding was calculated on DFT optimized structures using the gauge independent atomic orbital (GIAO) method. 27−29 The calculated isotope effect was compared to the experimental results.…”

Section: Introductionmentioning

confidence: 99%

C_α–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines

2014

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Experimental measurement of the contribution of H-bonding to intermolecular and intramolecular interactions that provide specificity to biological complex formation is an important aspect of macromolecular chemistry and structural biology. However, there are very few viable methods available to determine the energetic contribution of an individual hydrogen bond to binding and catalysis in biological systems. Therefore, the methods that use secondary deuterium isotope effects analyzed by NMR or equilibrium or kinetic isotope effect measurements are attractive ways to gain information on the H-bonding properties of an alcohol system, particularly in a biological environment. Here, we explore the anharmonic contribution to the C-H group when the O-H group of 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) forms an intermolecular H-bond with the amines by quantum mechanical calculations and by experimentally measuring the H/D effect by NMR. Within the framework of density functional theory, ab initio calculations were carried out for HFP in its two different conformational states and their H-bonded complexes with tertiary amines to determine the (13)C chemical shielding, change in their vibrational equilibrium distances, and the deuterium isotope effect on (13)C2 (secondary carbon) of HFP upon formation of complexes with tertiary amines. When C2-OH was involved in hydrogen bond formation (O-H as hydrogen donor), it weakened the geminal C2-H bond; it was reflected in the NMR chemical shift, coupling constant, and the equilibrium distances of the C-H bond. The first derivative of nuclear shielding at C2 in HFP was -48.94 and -50.73 ppm Å(-1) for anti and gauche conformations, respectively. In the complex, the values were -50.28 and -50.76 ppm Å(-1), respectively. The C-H stretching frequency was lower than the free monomer, indicating enhanced anharmonicity in the C-H bond in the complex form. In chloroform, HFP formed a complex with the amine; δC2 was 69.107 ppm for HFP-triethylamine and 68.766 ppm for HFP-d2-triethylamine and the difference in chemical shift, the ΔδC2 was 341 ppb. The enhanced anharmonicity in the hydrogen-bonded complex resulted in a larger vibrational equilibrium distance in C-H/D bonds. An analysis with the Morse potential function indicated that the enhanced anharmonicity encountered in the bond was the origin of a larger isotope effect and the equilibrium distances. Change in vibrational equilibrium distance and the deuterium isotope effect, as observed in the complex, could be used as parameters in monitoring the strength of the H-bond in small model systems with promising application in biomacromolecules.

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Fluoroalcohols—XXI. Infrared, matrix infrared and Raman spectra of 1,1,1-trifluoro-2-propanol and its three deuterated analogues

Cited by 32 publications

References 17 publications

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Infrared frequency effects of lone pair interactions with antibonding orbitals on adjacent atoms

C_α–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines

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Fluoroalcohols—XXI. Infrared, matrix infrared and Raman spectra of 1,1,1-trifluoro-2-propanol and its three deuterated analogues

Cited by 32 publications

References 17 publications

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Low‐Frequency CH Stretch Vibrations of Free Alkoxide Ions

Infrared frequency effects of lone pair interactions with antibonding orbitals on adjacent atoms

Cα–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines

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C_α–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines