Planar tetraco-ordinate carbon candidates: MNDO calculations on substituted phenyl-lithium dimers

1981 ◽  
pp. 260 ◽  
Author(s):  
Jayaraman Chandrasekhar ◽  
Paul Von Ragu� Schleyer
Keyword(s):  
Mndo Calculations ◽  
Lithium Dimers

Tautomerism of pyrazoline-5-thione and triazoline-5-thione studied by variable temperature photoelectron spectroscopy

1983 ◽  
Vol 61 (6) ◽  
pp. 1197-1203 ◽  
Author(s):  
Claude Guimon ◽  
Geneviève Pfister-Guillouzo ◽  
Mlkael Begtrup
Keyword(s):  
Gaseous Phase ◽  
Photoelectron Spectroscopy ◽  
Variable Temperature ◽  
Thermal Isomerization ◽  
Photoelectron Spectra ◽  
Planar Form ◽  
Mndo Calculations

Photoelectron spectra at variable temperatures demonstrate that the rate of thermal isomerization of pyrazoline-5-thione (1a) into methylthiopyrazole(s) in the gaseous phase is metal catalysed. Similar isomerizations of triazolethione (2a and 3a) are at best only slightly so.Furthermore, photoelectron spectra and MNDO calculations show that gaseous methylthiopyrazoles (1b and 1c) and methylthiotriazoles (2b and 2c) exist predominantly in planar form for the b isomer and in nonplanar form for the c isomer. The ΔH0 for the rotameric equilibria is 2.7–4.2 kJ•mol−1.

Chemistry of Fenchonesulfonic Acid Derivatives

1995 ◽  
Vol 50 (2) ◽  
pp. 283-288 ◽  
Author(s):  
Gabriele Wagner ◽  
Uwe Verfürth ◽  
Rudolf Herrmann
Keyword(s):  
Acetic Anhydride ◽  
Thionyl Chloride ◽  
Sulfonic Acid ◽  
Reaction Rate ◽  
Enantiomeric Excess ◽  
Methyl Group ◽  
Close Analogy ◽  
Chiral Sulfoxides ◽  
Mndo Calculations ◽  
Nmr Techniques

(1 S) - (+)-Fenchone is sulfonated by SO3 or H2SO4/acetic anhydride in the bridgehead methyl group. This could be confirmed by NMR techniques (INADEQUATE). The fenchonesulfonic acid obtained is converted (SOCl2/NH3) to the cyclic fenchonesulfonimide, which can be oxidized to the corresponding oxaziridine, in close analogy to 10-camphorsulfonimide. Improved procedures for this reaction sequences are given. During the treatment of the sulfonic acid with thionyl chloride, a byproduct with a rearranged bicyclic skeleton is observed whose structure has been determined by ozonolytic degradation and NMR techniques. A possible mechanism for this rearrangement is suggested, based on MNDO calculations of the intermediate carbocations. The fenchonesulfonyloxaziridine oxidizes sulfides to chiral sulfoxides with appreciable enantiomeric excess, but very low reaction rate. A comparison with camphor-derived oxaziridines having similar steric requirements is made.

Wechselwirkungen in Molekülkristallen, 126 [1,2]. Die Kationen-Solvatation in solvens-umhüllten und solvens-getrennten Ionen- Multipeln von 1,2,3,4-Tetraphenylcyclopentadienyl-Natrium-Salzen / Interactions in Molecular Crystals, 126 [1,2]. The Cation Solvation in Solvent-Shared and Solvent-Separated Ion Multiples of 1,2,3,4-Tetraphenylcyclopentadienyl-Sodium Salts

1997 ◽  
Vol 52 (4) ◽  
pp. 524-534 ◽  
Author(s):  
Hans Bock ◽  
Tim Hauck ◽  
Christian Nather ◽  
Zdenek Havlas
Keyword(s):  
Molecular Crystals ◽  
The Novel ◽  
Sodium Salts ◽  
Mndo Calculations ◽  
Counter Cation

The 1,2,3,4-tetraphenyl-shielded sodium cyclopentadienide, Na⊕[HC5⊖(C6H5)4], demonstrates essential facets of structure-determining cation solvation. The following solvent-shared or solvent-separated ion multiples have been crystallized from the respective aprotic ether solutions and structurally characterized: [(C29H21⊖)Na⊕(THF)7/2], [(C29H21⊖)Na⊕(DME)2]. [(C29H21⊖)]⊖[Na⊕(diglyme)2]⊕, [(C29H21⊖)]⊖[Na⊕(triglyme)2]⊕ and, from 18-crown-6 solution, the novel tripeldecker ion triple, [(C29H21⊖)]⊖[Na⊕(18-crown-6)Na⊕(18-crown-6)Na⊕(18-crown-6)]⊕⊕, which contains two Na⊕ counter cations between three 18-crown-6 discs. The structures, discussed in comparison with literature data and based on MNDO calculations, demonstrate the essential effects of Na⊕ counter cation solvation by various ether ligands.

MNDO calculations on tetrathiafulvalenes

1989 ◽  
Vol 32 (2) ◽  
pp. 179-190 ◽  
Author(s):  
Søren Bøwadt ◽  
Frank Jensen
Keyword(s):  
Mndo Calculations
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