State-to-State Quantum Mechanical Calculations of Rate Coefficients for the D+ + H2 → HD + H+ Reaction at Low Temperature

2013 ◽  
Vol 117 (39) ◽  
pp. 9778-9784 ◽  
Author(s):  
P. Honvault ◽  
Y. Scribano
Keyword(s):  
Low Temperature ◽  
Rate Coefficients ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations

Diastereoselective Addition of α-Metalated Sulfoxides to Imines Revisited: Mechanism, Computational Studies, and the Effect of External Chiral Ligands

2003 ◽  
Vol 68 (5) ◽  
pp. 885-898 ◽  
Author(s):  
Brian Pedersen ◽  
Tobias Rein ◽  
Inger Søtofte ◽  
Per-Ola Norrby ◽  
David Tanner
Keyword(s):  
Reaction Time ◽  
Low Temperature ◽  
Asymmetric Synthesis ◽  
Chiral Ligands ◽  
Quantum Mechanical ◽  
Kinetic Control ◽  
Computational Studies ◽  
Quantum Mechanical Calculations ◽  
Short Reaction Time ◽  
Diastereoselective Addition

Some new results on asymmetric synthesis via the addition of α-metalated methyl tolyl sulfoxides to imines are presented. Good diastereoselectivity (up to >98% d.e. for product 3g) can be obtained under conditions of kinetic control (short reaction time, low temperature). The transition state (a six-membered "flat chair") was probed by quantum mechanical calculations, which underpinned the idea of using external chiral ligands to enhance the diastereoselectivity of otherwise moderately selective reactions. In this way, the diastereomeric ratio of the product 3a could be raised from (84:16) to (>99:1) by use of a readily available C2-symmetric bis(sulfonamide) ligand.

scholarly journals Can polarity-inverted membranes self-assemble on Titan?

2020 ◽  
Vol 6 (4) ◽  
pp. eaax0272 ◽  
Author(s):  
H. Sandström ◽  
M. Rahm
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Lipid Bilayers ◽  
Self Assembly ◽  
Liquid Hydrocarbon ◽  
Bilayer Membrane ◽  
Cryogenic Liquid ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Dynamics Simulations

The environmental and chemical limits of life are two of the most central questions in astrobiology. Our understanding of life’s boundaries has implications on the efficacy of biosignature identification in exoplanet atmospheres and in the solar system. The lipid bilayer membrane is one of the central prerequisites for life as we know it. Previous studies based on molecular dynamics simulations have suggested that polarity-inverted membranes, azotosomes, made up of small nitrogen-containing molecules, are kinetically persistent and may function on cryogenic liquid hydrocarbon worlds, such as Saturn’s moon Titan. We here take the next step and evaluate the thermodynamic viability of azotosome formation. Quantum mechanical calculations predict that azotosomes are not viable candidates for self-assembly akin to lipid bilayers in liquid water. We argue that cell membranes may be unnecessary for hypothetical astrobiology under stringent anhydrous and low-temperature conditions akin to those of Titan.

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

Chemical accuracy from ‘Coulomb hole’ extrapolated molecular quantum-mechanical calculations

2001 ◽  
Vol 567-568 ◽  
pp. 375-384 ◽  
Author(s):  
K.L Bak ◽  
A Halkier ◽  
P Jørgensen ◽  
J Olsen ◽  
T Helgaker ◽  
...  
Keyword(s):  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Coulomb Hole
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