A molecular orbital study of the conformation (inversion and rotational barriers) and electronic properties of sulfamide

1989 ◽  
Vol 67 (12) ◽  
pp. 2227-2236 ◽  
Author(s):  
Otilia Mó ◽  
José L. G. De Paz ◽  
Manuel Yáñez ◽  
Ibon Alkorta ◽  
José Elguero ◽  
...  
Keyword(s):  
Multiple Bond ◽  
Amino Groups ◽  
Orbital Exponent ◽  
Nitrogen Inversion ◽  
Rotational Barriers ◽  
Polarization Functions ◽  
D Orbitals ◽  
Bond Character ◽  
Abinitio Calculations

Abinitio calculations have been used to study the conformational potential surface of sulfamide, by considering the S—N bond rotations and the nitrogen inversion processes. The lowest energy conformation (b) is found for a cis–trans arrangement of the amino groups, although conformations with cis–cis (a), trans–trans (c), and near staggered (c′) arrangements lie close in energy. Nitrogen inversion barriers are very low, and consequently one may expect forms b and c′ to be the only ones present in the gas phase. Conformer a is very polar, its dipole moment being twice that of b, so it may be favored in condensed media or in polar-solvent solutions. The relative stability of the different isomers is governed by interactions between the amino protons and between the nitrogen lone pairs. Our results show that d–π backbonding, involving the d orbitals on sulfur, is responsible for the multiple bond character of the S—O linkage, but is very small in the S—N interactions. The role of the sulfur d-orbital exponent, when a 6-31G* basis is used, is analyzed on a series of model compounds containing SII, SIV, and SVI. Although the inclusion of d functions on sulfur is crucial to describing correctly the bonding in sulfamide, the results obtained do not change appreciably if a second set of d functions is centered on sulfur. Nevertheless, only when polarization functions are also included for first-row atoms is the description of the system reliable. Keywords: sulfamide, inversion and rotational barriers, sulfur d-functions.

d Orbitals in the noble-gas dihalides

1970 ◽  
Vol 48 (17) ◽  
pp. 2695-2701 ◽  
Author(s):  
R. C. Catton ◽  
K. A. R. Mitchell
Keyword(s):  
Noble Gas ◽  
Valence Bond ◽  
Ionic Character ◽  
Orbital Exponent ◽  
Covalent Bonds ◽  
Model Calculations ◽  
Pair Bonds ◽  
Electron Repulsion Integrals ◽  
D Orbitals

Model calculations are reported for ArF2, KrF2, XeF2, ArCl2, KrCl2, and XeCl2. The approach is to compare the energies of a number of valence-bond structures for each molecule. The calculations use Slater-type radial functions and simplify the electron repulsion integrals with the Mulliken approximation. Energies are optimized by varying the d orbital exponent and a parameter which governs the ionic character of the covalent bonds. For all the molecules it is found that the structures such as (X—M+X− + X−M+—X) and X−M2+X−, which maintain the octet rule and exclude the use of d orbitals, are less stable than the structure X—M—X which implies localized electron-pair bonds based on pd hybrids at the noble-gas atom M.Approximate molecular wave functions are obtained from a configuration interaction calculation, and the general conclusion is that the valence-bond structures incorporating d orbitals become more important as the atomic number of the central atom increases. A preliminary study of the role of the [Formula: see text] orbital is also presented, but it seems this orbital contributes mainly as a polarization effect.

Nonadditive effects of polysubstitution in CH4 and CH3: a test of abinitio and semiempirical MO methods

1983 ◽  
Vol 61 (7) ◽  
pp. 1567-1572 ◽  
Author(s):  
N. Colin Baird
Keyword(s):  
Basis Set ◽  
Semiempirical Methods ◽  
Valence Shell ◽  
Bond Lengths ◽  
Hartree Fock ◽  
Nonadditive Effects ◽  
D Orbitals ◽  
Split Valence ◽  
Abinitio Calculations

The effects to the bond lengths and molecular energy of making multiple substitutions at the same carbon atom in methane and the methyl free radical are studied using various molecular orbital methods. All abinitio calculations were based upon the Hartree–Fock formalism (unrestricted in the case of free radicals) and employed the STO-3G (with d orbitals on chlorine), 3-21G, and 4-31G bases, the last both with and without a set of Gaussian d orbitals on the carbon. The semiempirical methods used were the MINDO/3 and MNDO methods of Dewar and co-workers; computations for polysubstituted ethanes by these two methods also arc reported. The abinito methods which use a split valence shell basis set account very well for the trends in bond lengths and heats of formation, at least when the polysubstituent is fluorine or hydroxyl. In contrast, the semiempirical calculations and the abinitio STO-3G results gave very poor results. Finally, the role of interactions between the AH bonds in a variety of hydrides AHn is illustrated using experimental energetics.

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

On the role of amino groups and aliphatic hydroxyls in the structure of human haemoglobin

1963 ◽  
Vol 28 (12) ◽  
pp. 3290-3296
Author(s):  
Z. Vodrážka ◽  
J. Salák ◽  
J. Čejka
Keyword(s):  
Amino Groups ◽  
Human Haemoglobin

scholarly journals Role of Lysyl ε-Amino Groups in Adenosine Diphosphate Binding and Catalytic Activity of Pyruvate Kinase

1971 ◽  
Vol 246 (4) ◽  
pp. 946-953 ◽  
Author(s):  
Paul F. Hollenberg ◽  
Michael Flashner ◽  
Minor J. Coon
Keyword(s):  
Catalytic Activity ◽  
Pyruvate Kinase ◽  
Adenosine Diphosphate ◽  
Amino Groups

scholarly journals On the Role of Amino Groups in the Structure and Function of Glutamate Dehydrogenase

1966 ◽  
Vol 241 (16) ◽  
pp. 3652-3660 ◽  
Author(s):  
Roberta F. Colman ◽  
Carl Frieden
Keyword(s):  
Glutamate Dehydrogenase ◽  
Structure And Function ◽  
Amino Groups ◽  
And Function

ChemInform Abstract: THE ROLE OF D ORBITALS ON PHOSPHORUS IN THE BONDING OF TRIMETHYLPHOSPHINE AND TRIS(TRIFLUOROMETHYL)PHOSPHINE

1982 ◽  
Vol 13 (33) ◽  
Author(s):  
M.-H. WHANGBO ◽  
K. R. STEWART
Keyword(s):  
D Orbitals

The role of sulfur d-orbitals in the charge-transfer complexation of carbonyl cyanide with alkyl sulfides

Tetrahedron ◽  
1976 ◽  
Vol 32 (12) ◽  
pp. 1345-1346 ◽  
Author(s):  
T. Fueno ◽  
Y. Yonezawa
Keyword(s):  
Charge Transfer ◽  
Carbonyl Cyanide ◽  
Charge Transfer Complexation ◽  
D Orbitals

scholarly journals Role of amino groups in formation of human lymphocyte-xenogeneic erythrocyte rosettes; a proposed mechanism for antigen recognition.

1975 ◽  
Vol 72 (2) ◽  
pp. 697-700 ◽  
Author(s):  
P. Lalezari ◽  
S. L. Nehlsen ◽  
J. Novodoff ◽  
I. Lalezari
Keyword(s):  
Human Lymphocyte ◽  
Antigen Recognition ◽  
Amino Groups
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