Search results for "Computation"
showing 10 items of 7362 documents
NMR spectroscopy in environmental chemistry:1H and13C NMR chemical shift assignments of chlorinated dibenzothiophenes based on two-dimensional NMR te…
1999
Ab initio study of lithiated N-methylpyridones
1996
Liquid-phase Chemistry
2003
Inherently Chiral Calixarenes
1994
Due to the nonplanarity of the basic 1 n -metacyclophane system, calixarenes and resorcarenes can be transformed into molecules with inherent chirality. Various attempts to achieve this goal are reviewed. Special emphasis is given to derivatives with C n -symmetry, including derivatives of spherand calixarenes and other calixarene-like macrocycles.
1H and13C NMR assignments and conformational analysis of some podocarpene derivatives
2000
This paper reports on the assignment of the 1 Ha nd 13 C NMR spectra of five podocarpene derivatives. Resonance assignments were made on the basis of one- and two-dimensional NMR techniques which included 1 H, 13 C, DEPT and HMQC and also 1D NOE difference spectroscopy. The ratio of the different conformers in the six- membered C-ring of the podocarpene system was determined by molecular mechanics calculations and analysis of proton spin-spin coupling constants. Copyright © 2000 John Wiley & Sons, Ltd.
Ab initio study of halogenated diphenyl ethers. NMR chemical shift prediction
2000
Theoretical study of degenerate Boulton-Katritzky rearrangements. Semiempirical and ab initio procedures
1998
Abstract A theoretical study of degenerate Boulton–Katritzky rearrangements concerning the anions of the 3-formylamino-1,2,4-oxadiazole, 3-formylmethyl-isoxazole and 3-hydroxy-iminomethyl-1,2,5-oxadiazole has been carried out by using semiempirical MNDO and ab initio Hartree–Fock procedures. Different transition structures and reactive pathways were obtained in the two cases. Semiempirical treatment shows asymmetrical transition states and non-concerted processes via symmetrical intermediates. By contrast, ab initio procedures describe concerted and synchronous processes involving symmetrically-located transition states. Some comments and criticisms on the theoretical treatment of these typ…
ChemInform Abstract: New Structural Aspects of 3-Vinyl-1H-indoles for Predicting the Outcome of Diels-Alder Reactions
1989
Some selected 3-vinyl-1H-indoles have been synthesised and the first13C-NMR studies performed; in addition He(Iα) photoelectron spectra and the results of perturbation MO calculations of some examples of this class of compounds are presented. The molecular characteristics obtained thereby can be used to predict the results of [π4s+π2s]-cycloaddition reactions with 3-vinylindoles.
Influence of Benzoannulation on the Molecular and Electronic Structures of Tetracyanoquinodimethanes
1996
The molecular and electronic structures of TCNQ and its π-extended derivatives benzo-TCNQ and TCAQ have been investigated using the semiempirical PM3 method and ab initio 6-31G* calculations. The s...
ChemInform Abstract: The Reaction of Aromatic α,β-Unsaturated Ketones with 4,5- Diamino-1,6-dihydropyrimidin-6-ones.
2010
The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m. The structure elucidation of the products is based on detailed nmr investigations including selective 13C[1H] decoupling experiments.