Microwave spectra and structure of the cyclopropanecarboxylic acid-formic acid dimer

Pejlovas, Aaron M.; Lin, Wei; Kukolich, Stephen G.

doi:10.1063/1.4931923

Cited by 13 publications

(6 citation statements)

References 25 publications

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“…No tunneling splittings were observed for formic acid-formamide, 10 1,2-cyclohexanedione-FA 11 or cyclopropanecarboxylic acid-FA. 12 No evidence for proton tunneling was observed in the present work on the Maleimide -Formic Acid complex.…”

Section: Introductioncontrasting

confidence: 64%

Rotational spectra and gas phase structure of the maleimide – Formic acid doubly hydrogen bonded dimer

Pejlovas

Kukolich

2016

Journal of Molecular Spectroscopy

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Rotational transitions were measured for the maleimide-formic acid doubly hydrogen bonded dimer using a Flygare-Balle type pulsed-beam Fourier transform microwave spectrometer. No splittings caused by possible concerted double proton tunneling motion were observed. Experimental rotational constants (MHz), quadrupole coupling constants (MHz), and centrifugal distortion constants (kHz) were determined for the parent and three deuterium substituted isotopologues. The values for the parent are A = 2415.0297(10), B = 784.37494(38), C = 592.44190(33), D J = 0.0616(64), D JK =-0.118(35), D K =-1.38(15), 1.5χ aa = 2.083(14), and 0.25(χ bb-χ cc) = 1.1565(29). The hydrogen bond lengths were determined using a nonlinear least squares structure fitting program. Rotational constants for this complex are consistent with a planar structure, with an inertial defect of ∆ =-0.528 amu Å 2. The B3LYP calculation yielded rotational constants within 0.1% of the experimental values.

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Section: Introductioncontrasting

confidence: 64%

Rotational spectra and gas phase structure of the maleimide – Formic acid doubly hydrogen bonded dimer

Pejlovas

Kukolich

2016

Journal of Molecular Spectroscopy

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“…It appears the tunneling frequencies tend to decrease and the probability of observing tunneling splittings in the spectra becomes less as the potential becomes more asymmetric. No tunneling splittings were observed for formic acid-formamide, 6 1,2-cyclohexanedione-formic acid 7 or cyclopropanecarboxylic acid-formic acid, 8 or the maleimide -formic acid complex. 9 Tropolone -formic acid has the C2v(m) symmetry but splittings were not observed due to the high barrier.…”

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confidence: 89%

Synthesis, microwave spectra, x-ray structure, and high-level theoretical calculations for formamidinium formate

Zhou

Aitken

Cardinaud

et al. 2019

The Journal of Chemical Physics

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An efficient synthesis of formamidinium formate is described. The experimental x-ray structure shows both internal and external H-bonding to surrounding molecules. However, in the gas phase this compound occurs as a doubly hydrogen bonded dimer. This doubly hydrogen-bonded structure is quite different from the solid state structure. Microwave spectra were measured in the 6-14 GHz range using a pulsed-beam Fourier transform microwave spectrometer. The two nonequivalent N-atoms exhibit distinct quadrupole coupling. The rotational, centrifugal distortion and quadrupole coupling constants determined from the spectra have values: A = 5880.05(2), B = 2148.7710(2), C = 1575.23473(13), 1.5 χaa (N1) =1.715(3), 0.5(χbb-χcc)(N1) =-1.333(4), 1.5χaa (N2) = 0.381(2), 0.25(χbb-χcc)(N2) =-0.0324(2), and D J = 0.002145(5) MHz. The experimental inertial defect, ∆ =-0.243 amu Å 2 , is consistent with a planar structure.

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“…Known experimental splittings for hydrogen atom tunneling span a range of more than eight orders of magnitudes, with most of them being (far) smaller than 1 cm

(

0.01 kJ mol

) [ 15 ]. For this reason, localization is the typical, but not the strict, outcome from symmetry breaking by chemical [ 3 , 16 , 17 , 18 , 19 ] or isotopic [ 4 , 5 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ] substitution, internal rotation of molecular groups [ 6 , 16 , 20 , 24 , 29 ], or from environmental influences such as solvation [ 16 , 30 ], matrix embedding [ 3 , 31 , 32 ] or crystallization [ 33 ]. However, delocalization can still be observed upon excitation if either the barrier [ 3 , 5 , 21 , 25 , 26 , 29 ] or the energetic asymmetry [ 22 , 34 ] are sufficiently lowered.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

et al. 2021

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Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second most stable torsional conformer, despite computational predictions that it is only very slightly higher in energy than the global minimum. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modeling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm−1hc for the protiated and deuterated alcohol, respectively, which further shrink to 9(1) and 3(1) cm−1hc upon OH or OD stretch excitation. Comparisons are made with the more strongly asymmetric monoterpenols borneol and isopinocampheol as well as with the symmetric, rapidly tunneling propargyl alcohol. In addition, the third—in contrast localized—torsional conformer and the most stable dimer are assigned for α-fenchol, as well as the two most stable dimers for propargyl alcohol.

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Microwave spectra and structure of the cyclopropanecarboxylic acid-formic acid dimer

Cited by 13 publications

References 25 publications

Rotational spectra and gas phase structure of the maleimide – Formic acid doubly hydrogen bonded dimer

Rotational spectra and gas phase structure of the maleimide – Formic acid doubly hydrogen bonded dimer

Synthesis, microwave spectra, x-ray structure, and high-level theoretical calculations for formamidinium formate

Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol

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