The shape of urea

Godfrey, Peter D.; Brown, R. D.; Hunter, Andrew

doi:10.1016/s0022-2860(97)00176-2

Cited by 98 publications

(110 citation statements)

References 23 publications

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“…It may be noted that several parameters of the equilibrium structure are rather far from the r s structure parameters derived in ref 61. This is not surprising because it is well-established that r s (XH) distances are not reliable.…”

Section: Equilibrium and Effective Structuresmentioning

confidence: 81%

“…Similarly to formamide, planarity of urea has been the subject of much debate. The early studies are reviewed nicely by Godfrey et al 61 These authors also analyzed the MW spectra of several isotopologues of urea which allowed them to obtain an r s structure (Table 4). They found that the conformer of lowest energy has C 2 symmetry and that a structure of C s symmetry has a slightly higher energy.…”

Section: Equilibrium and Effective Structuresmentioning

confidence: 99%

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Equilibrium vs Ground-State Planarity of the CONH Linkage

et al. 2007

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Planarity of the XC(d)NHY linkage has been investigated in unprecedented detail in a number of relatively simple compounds, including formamide (, and methyl carbamate (X ) OCH 3 , Y ) H). Reliable estimates of the equilibrium structures of formamide, cyanamide, acetamide, urea, carbamic acid, methylamine, dimethyl ether, and methyl carbamate are derived, mostly for the first time. It is shown that formamide, considered prototypical for the amide linkage, is not typical as it has a planar equilibrium amide linkage corresponding to a single-minimum inversion potential around N. In contrast, several molecules containing the CONH linkage seem to have a pyramidalized nitrogen at equilibrium and a double-minimum inversion potential with a very small inversion barrier allowing for an effectively planar ground-state structure. Observables of rotational spectroscopy, including ground-state inertial defects, quadrupole coupling and centrifugal distortion constants, and dipole moment components, as well as equilibrium CdO and C-N bond lengths are reviewed in their ability to indicate the planarity of the effective and possibly the equilibrium structures.

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Section: Equilibrium and Effective Structuresmentioning

confidence: 81%

Section: Equilibrium and Effective Structuresmentioning

confidence: 99%

Equilibrium vs Ground-State Planarity of the CONH Linkage

et al. 2007

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“…This is an indication of the inversion barrier of the amide group. We should note, however, from the ®ndings of Godfrey et al [19], that there is another intermediate way to go from the C 2 to the C s structure without proceeding though C 2v intermediate, but through an energy barrier that is four times lower in Table 3. Gas-phase calculated frequencies (cm )1 ) for the parent and deuterated urea molecule a [19].…”

Section: Gas Phase Urea Moleculementioning

confidence: 80%

Vibrational and theoretical studies of urea and magnesium-urea complexes

Raptis

Anastassopoulou

Théophanides

2000

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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The molecular structure and IR spectra of urea, H 2 NCONH 2 , in gas phase and in acetonitrile solution, as well as of the two complexes [MgU 4 Cl 2 ] and [MgU 6 ]Cl 2 have been observed. The in¯uence of environmental changes to geometry and spectra are shown. Various basis sets have been employed to safeguard the validity of the reported ®ndings, using polarization functions for all calculations to get the correct pyramidal amide con®guration. The erroneous low energy of the C 2v symmetry group, after the addition of the ZPVE correction, is discussed. For the solvated urea molecule a reduction of the energy barrier, compared to the gas phase urea, between the two minimum con®gurations, C 2 and C s , and the planar geometry, is observed. The lowest energy minimum in acetonitrile is found to be the C 2 symmetry group, while for the two complexes, the local symmetry of urea is C s or C 2 depending on the complex, or even on the coordination position of urea in the complex. The wagging motion of the amide group is also discussed in all the studied urea species. The computed geometries and most of the spectroscopic results are in good agreement with the available experimental data.

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“…[55][56][57][58][59] The heavy atoms (O-C-N) of urea are co-planar, but the NH 2 groups are pyramidal. This results in three key geometries, C 2 , C 2v and C s 70 urea (ESI, Figure S6).…”

Section: Urea Monomer and Urea-urea Dimersmentioning

confidence: 99%

“…This results in three key geometries, C 2 , C 2v and C s 70 urea (ESI, Figure S6). [56][57][58] The energy difference between the three conformers is small, and depends on the level of theory.…”

Section: Urea Monomer and Urea-urea Dimersmentioning

confidence: 99%

Doubly ionic hydrogen bond interactions within the choline chloride–urea deep eutectic solvent

Ashworth

Matthews

Welton

et al. 2016

Phys. Chem. Chem. Phys.

311

254

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5Deep eutectic solvents (DESs) are exemplars of systems with the ability to form neutral, ionic and doubly ionic H-bonds. Herein, the pairwise interactions of the constituent components of the choline chlorideurea DES are examined. Evidence is found for a tripodal CH⋅⋅⋅Cl doubly ionic H-bond motif. Moreover it is found that the covalency of doubly ionic H-bonds can be greater than, or comparable with, neutral and ionic examples. In contrast to many traditional solvents, an "alphabet soup" of many different types 10 of H-bond (OH⋅⋅⋅O=C, NH⋅⋅⋅O=C, OH⋅⋅⋅Cl, NH⋅⋅⋅Cl, OH⋅⋅⋅NH, CH⋅⋅⋅Cl, CH⋅⋅⋅O=C, NH⋅⋅⋅OH and NH⋅⋅⋅NH) can form. These H-bonds exhibit substantial flexibility in terms of number and strength. It is anticipated that H-bonding will have a significant impact on the entropy of the system and thus could play an important role in the formation of the eutectic.

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The shape of urea

Cited by 98 publications

References 23 publications

Equilibrium vs Ground-State Planarity of the CONH Linkage

Equilibrium vs Ground-State Planarity of the CONH Linkage

Vibrational and theoretical studies of urea and magnesium-urea complexes

Doubly ionic hydrogen bond interactions within the choline chloride–urea deep eutectic solvent

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