Rotational Barriers in Vinyl Compounds

1981 ◽  
pp. 371-377
Author(s):  
George R. Maré
Keyword(s):  
Rotational Barriers

Catalyst-Control over Sixfold Stereogenicity

2020 ◽  
Author(s):  
Xingxing Wu ◽  
Reto M. Witzig ◽  
Rodolphe Beaud ◽  
Christian Fischer ◽  
Daniel Häussinger ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Higher Order ◽  
Binary Codes ◽  
Rotational Barriers ◽  
Molecular Architectures

Governing higher-order stereogenicity is a long-standing goal in stereoselective catalysis, because it allows to achieve selectivity for more than a twofold number of stereoisomers per stereogenic unit. Current methods warrant control over the power of two stereoisomers and the configurations are routinely assigned using the descriptors ( R ) and ( S ), or related binary codes. In contrast, conformational analysis ranges beyond this dualistic treatment of stereoisomerism, which constitutes an unmet challenge for catalyst stereocontrolled processes. Herein, we now report that sixfold stereogenicity can be governed by stereoselective catalysis. By controlling a configurationally stable stereogenic axis with six large rotational barriers, a catalytic [2+2+2]-cyclotrimerization selectively governs the formation of one out of six stereoisomers with up to 0:0:2:98:0:0 stereocontrol. The underpinnings of conformational analysis and stereoselective catalysis are thereby conceptually reunited. Novel molecular architectures featuring distinct chemical topologies and unexplored chemical designs are anticipated from catalystcontrol over higher-order stereogenicities

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.

scholarly journals Structural Parameters and Internal Rotational Barriers of tert-Butylammonium Ion: AM1 and ab initio Calculations

1992 ◽  
Vol 47 (12) ◽  
pp. 1255-1256
Author(s):  
Hiroyuki Ishida ◽  
Yoshihiro Kubozono ◽  
Setsuo Kashino ◽  
Ryuichi Ikeda
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Internal Rotation ◽  
Barrier Height ◽  
Structural Parameters ◽  
Mo Calculations ◽  
Ab Initio Mo Calculations ◽  
Rotational Barriers ◽  
Ab Initio Mo ◽  
Internal Rotational Barriers

Semiempirical and ab initio MO calculations were performed to estimate the structural parameters of tert-butylammonium ion and its potential energies for the internal rotation of the CH3 and NH3+ groups. The barrier height for the rotation of NH3+ was found to be lower than for that of CH3 , corresponding to the C - N bond being longer than the C - C bond.

scholarly journals Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations

2013 ◽  
Vol 135 (25) ◽  
pp. 9366-9376 ◽  
Author(s):  
Cyprien Lemouchi ◽  
Konstantinos Iliopoulos ◽  
Leokadiya Zorina ◽  
Sergey Simonov ◽  
Pawel Wzietek ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Molecular Rotors ◽  
Inversion Symmetry ◽  
Rotational Barriers ◽  
Correlated Motion ◽  
Space Inversion

High rotational barriers about CN bonds in aryl substituted heterocyclic compounds lacking bulky ortho substituents

1972 ◽  
Vol 13 (51) ◽  
pp. 5239-5240 ◽  
Author(s):  
L.D. Colebrook ◽  
H.G. Giles ◽  
A. Rosowsky
Keyword(s):  
Heterocyclic Compounds ◽  
Rotational Barriers
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