The effect of deuterium substitution in the amino group on the internal-rotation barrier of acetamide

Hirota, Eizi; Kawashima, Yasunaru; Usami, Tsuyoshi; Seto, Koichi

doi:10.1016/j.jms.2009.12.008

Cited by 6 publications

(13 citation statements)

References 19 publications

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“…According to our results on acetamide [15], the deuterium substitution effect in the amino group on the CH 3 internal-rotation potential may be interpreted to be due to the change in the electronic structure of the central peptide linkage. We may transfer the same mechanism to NMFA; the change in electronic structure in trans upon imino deuteration takes place such that the V 3 decreases, while that in cis makes V 3 higher.…”

Section: Ch 3 Internal-rotation Potential Barriermentioning

confidence: 59%

“…We have demonstrated [15] that in acetamide the NH 2 wagging is coupled with the CH 3 internal rotation to produce a quite large V 6 term to the potential function of the latter. Unfortunately, we could not observe spectra of NMFA in the excited states of CH 3 internal rotation, prohibiting us from deriving the V 6 constant for this molecule.…”

Section: Ch 3 Internal-rotation Potential Barriermentioning

confidence: 86%

“…In order to determine the molecular structure of NMFA, we observed spectra of the 13 C, 15 N and 18 O isotopomers in natural abundance. For ease of detecting and analyzing the spectra, we limited the observations to the trans form in the A internal-rotation state, i.e.…”

Section: Trans Isotopomers In the A Statementioning

confidence: 99%

“…It would thus be interesting to detect spectra of the N-D species in the E internal-rotation state and to derive the potential barrier V 3 for this species, which might provide us with further information on the coupling between the CH 3 internal rotation and the N-H out-of-plane bending and on the origin of V 3 . In this respect, we should mention our recent study of acetamide by FTMW spectroscopy [15]. This molecule has been known to have an extremely low V 3 : 25.043857 cm À1 [16], and we have traced the origin of this low barrier by examining the effect of deuterium substitution in the amino group.…”

Section: Introductionmentioning

confidence: 95%

“…The cis/trans ratio reported ranges from 11/89 to 5/95 at room temperature. Dorman and Bovey [9] and Nakanishi and Roberts [10] extended the method to 13 C and 15 N resonances and demonstrated that these signals were useful not only in determining the cis/trans abundance ratio, but also in elucidating the conformations of peptides as a whole. Kitano and Kuchitsu [11] investigated NMFA by electron diffraction and determined the molecular structure (r g and h a ) of the trans form, but they failed to detect the cis form.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy and ab initio calculations of N-methylformamide

Kawashima

Usami

Suenram

et al. 2010

Journal of Molecular Spectroscopy

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Section: Ch 3 Internal-rotation Potential Barriermentioning

confidence: 59%

Section: Ch 3 Internal-rotation Potential Barriermentioning

confidence: 86%

Section: Trans Isotopomers In the A Statementioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy and ab initio calculations of N-methylformamide

Kawashima

Usami

Suenram

et al. 2010

Journal of Molecular Spectroscopy

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Analysis of Uncertainty in the Calculation of Ideal-Gas Thermodynamic Properties Using the One-Dimensional Hindered Rotor (1-DHR) Model

2016

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The uncertainty analysis of the calculation of ideal-gas thermodynamic properties using the one-dimensional hindered rotor (1-DHR), which is designed for quantum chemical treatment of internal rotations, is presented. The sensitivity of ideal-gas heat capacities and entropies to the input parameters of the 1-DHR model, that is, the reduced moments of inertia and barriers to internal rotation, is analyzed and evaluated. The calculations of energy barriers to internal rotations using the B3-LYP functional coupled with six basis sets and the empirical D3 correction accounting for dispersion interactions for a set of 60 molecular structures containing internal rotation motions were also performed, compared with available experimental values, and statistically evaluated to estimate the impact of uncertainty associated with the calculated barriers to internal rotation (15% on average, underestimated in two-thirds of cases) on ideal-gas thermodynamic properties.

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Conformational Properties of cis- and trans-N-Cyclopropylformamide Studied by Microwave Spectroscopy and Quantum Chemical Calculations

2015

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The microwave spectra of cis- and trans-N-cyclopropylformamide, C3H5NHC(═O)H, have been investigated in the 31-123 GHz spectral region at room temperature. Rotational isomerism about the Cring-N bond is possible for both cis and trans. MP2/cc-pVTZ and CCSD/cc-pVTZ calculations indicate that there are two conformers in the case of cis, called Cis I and Cis II, while only one rotamer, denoted Trans, exists for trans-N-cyclopropylformamide. The quantum chemical methods predict that Cis I has an electronic energy that is 8-9 kJ/mol higher than the energy of Cis II. The CCSD H-Cring-N-H dihedral angle is 0.0° in Cis I, 93.0° in Cis II and 79.9° in Trans. The CCSD and MP2 calculations predict a slightly nonplanar structure for the amide moiety in both Trans and Cis II, whereas Cis I is computed to have a planar amide group bisecting the cyclopropyl ring. Surprisingly, the MP2 and CCSD methods predict practically the same energy for Trans and Cis II. The spectra of Cis II in the ground state and in two vibrationally excited states were assigned, while the spectrum of Cis I was not found presumably because of a low Boltzmann population due to a relatively large energy difference (8-9 kJ/mol). The spectra of the ground vibrational state and seven vibrationally excited states of Trans, were assigned. Vibrational frequencies of several of the excited state of both Cis II and Trans were determined by relative intensity measurements. The experimental and CCSD rotational constants are in satisfactory agreement. The MP2 values of the quartic centrifugal distortion constants of both species are in relatively poor agreement with their experimental counterparts. The MP2 vibration-rotation constants and sextic centrifugal distortion constants have little resemblance with the corresponding experimental values.

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The effect of deuterium substitution in the amino group on the internal-rotation barrier of acetamide

Cited by 6 publications

References 19 publications

Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy and ab initio calculations of N-methylformamide

Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy and ab initio calculations of N-methylformamide

Analysis of Uncertainty in the Calculation of Ideal-Gas Thermodynamic Properties Using the One-Dimensional Hindered Rotor (1-DHR) Model

Conformational Properties of cis- and trans-N-Cyclopropylformamide Studied by Microwave Spectroscopy and Quantum Chemical Calculations

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