Neutron diffraction at 16 K and <i>ab initio</i> molecular-orbital studies of the structure of formamide oxime

Ruble, J. R.; McMullan, R. K.; Defrees, D. J.; Pople, J. A.

doi:10.1107/s0567740881005980

Cited by 28 publications

(11 citation statements)

References 10 publications

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“…The order of the energetic stability of the A isomers ( A1 > A5 > A7 > A2 ) is the same at each level of theory and confirms that the Z configuration is the most favorable for amidoximes. This configuration has been also found for the crystal structures of other amidoximes, e.g., H 2 NCHNOH, H 2 NC(Ph)NOH, and its derivatives, and also H 2 NC(2‐Pyridyl)NOH …”

Section: Resultssupporting

confidence: 75%

“…PAOX can be considered as the diaza derivative of benzamidoxime {H 2 NC(Ph)NOH}. Benzamidoxime itself, being the hydroxy derivative of benzamidine, displays prototropic tautomerism . It possesses two labile protons, one at the hydroxy O atom and the other one at the amino N atom, and four conjugated sites, the O‐hydroxy, C‐functional, N‐imino, and N‐amino atoms.…”

Section: Resultsmentioning

confidence: 99%

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Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

Głębocka

Raczyńska

Chylewska

et al. 2016

J of Physical Organic Chem

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The results of the first structural studies (with the use of both experimental and theoretical methods) on pyrazine‐2‐amidoxime (PAOX) were shown and discussed. FT‐IR spectra were recorded in different concentrations of the PAOX in apolar solvent to check the possibility of the inter‐ or intramolecular hydrogen‐bond formation. All possible tautomers–rotamers of PAOX were then theoretically considered at the DFT(B3LYP)/6‐311+G** level in vacuo. For selected isomers, calculations were also performed at higher levels of theory {B3LYP/6‐311+G(3df,2p) and G3B3}. Based on the results of DFT calculations, the most stable isomers were found, and their total free energies and infrared spectra were calculated. The energy variation plots for the N8C7N9O10 and N1C2C7N9 dihedral angles were also computed to find two energy barriers, one for E/Z isomerization around the C7N9 double bond and the other one for rotation of the pyrazinyl ring around the C2C7 single bond. The results show that the stability of the PAOX isomers strongly depend on their configuration and orientation of the substituents. The possibilities of inter‐ and intramolecular hydrogen bonds were also experimentally and theoretically checked. Finally, a potential of mean force was determined in CHCl3 for a dimer of PAOX with hexamethylphosphoramide. Both, experimental and theoretical results are in agreement. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

Głębocka

Raczyńska

Chylewska

et al. 2016

J of Physical Organic Chem

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“…8 Calculations were done in both the STO-3G and 3-21G basis sets, using the "Berny" optimization scheme for the energy as given in the GAUSSIAN 82 program package.12 The same program package was used to calculate the energy of (E)-acetaldoxime in the 6-31G" basis set (which includes polarization functions on the heavy atoms). In the search for the optimum geometry of the two oximes, all the parameters were optimized given the constraints of the structure of the (El-conformer of the oximes (see Figs.…”

Section: Methodsmentioning

confidence: 99%

A conformational study of a biologically active conjugated syn‐oxime

Venanzi

1988

J Comput Chem

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The conjugated system (El-tiglaldoxime is the simplest example of a perillartine analog which exhibits sweetness with a taste potency greater than sucrose with almost no bitter aftertaste. In previous studies, the structure of this biologically active compound has been assumed to be planar with the C = C double bond trans to the C=N bond of the oxime moiety. In this article a conformational analysis of this molecule is reported. The results indicate that, although the trans conformer of the planar molecule is indeed the global minimum, other conformers lie within a few kilocalories of this minimum. Hence, other accessible conformations may be available for interaction with the receptor and, therefore, may be biologically active. The structural parameters obtained for this conjugated syn-oxime are nearly identical to those of (El-acetaldoxime. This fact has implications for the transferability of these parameters to the more complicated perillartine analogs.

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“…The quantum-chemical calculations for the oximes have been reported. − Nguyen and Ha 12 have studied the aldoximes (RCHNOH, R = H, CH 3 , NH 2 , OH, and F) by ab initio SCF techniques, employing the double-zeta (DZ) basis sets. Glaser and Streitwieser 14 performed ab initio studies for several conformers of acetaldoxime and carbanions of acetaldoxime.…”

Section: Introductionmentioning

confidence: 99%

Molecular Structures and Rotational Potential Energy Surfaces of E and Z Geometrical Isomers of Propionaldehyde Oxime: ab Initio and DFT Studies

et al. 1997

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Molecular structure and conformational stability of E and Z geometrical isomers of propionaldehyde oxime (C(1)H3C(2)H2C(3)HNOH) have been studied by using the ab initio and DFT methods. The molecular geometries were optimized by employing the atomic basis sets 6-31G* at the HF-SCF and MP2 levels of theory in the ab initio method. The basis sets 6-31G and 6-31G* are used in the BLYP method of DFT to optimize the molecule. The optimized structural parameters of the above methods are discussed in the light of the electron diffraction results of the molecule. The variations in CN bond length, C1C2C3 and C2C3N angles of the sp and ac conformers of E isomer and of the ap conformer of Z isomer have been discussed in terms of nonbonding interactions of CH3 and NOH groups. The rotational potential energy surfaces of E and Z isomers were obtained for the C2−C3 rotational angle of propionaldehyde oxime at HF/6-31G*, MP2/6-31G*, and BLYP/6-31G* levels of theory. The global minimum occurs at φ(CCCN) = 120° and φ = 0° for the ac and sp conformations of the E isomer and φ = 180° for the Z isomer. The ac form is found to be more stable than the sp form by 0.16 kcal/mol in HF/6-31G* level of theory; this difference agrees very well with the experimental value of 0.15 kcal/mol. The rotational potential curve of Z form shows that it has large-amplitude motion. The chemical hardness values obtained for the different conformers of the two isomers are in disagreement with the statement that the higher stable conformation has higher chemical hardness, but the trend obeys the general trend of oxime molecules. The Fourier decompositions of the rotational potential of the propionaldehyde oxime are analyzed.

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Neutron diffraction at 16 K and ab initio molecular-orbital studies of the structure of formamide oxime

Abstract: The crystal structure of formamide oxime (N-hydroxymethaneimidamide), CH4N20, has been refined using single-crystal neutron diffraction data measured at 16K [P212~21, a = 8.187 (1)

Cited by 28 publications

References 10 publications

Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

Experimental (FT‐IR) and theoretical (DFT) studies on prototropy and H‐bond formation for pyrazine‐2‐amidoxime

A conformational study of a biologically active conjugated syn‐oxime

Molecular Structures and Rotational Potential Energy Surfaces of E and Z Geometrical Isomers of Propionaldehyde Oxime: ab Initio and DFT Studies

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