Ab initio calculations of vibrational circular dichroism in propylene oxide: geometry and force field dependence

1988 ◽  
Vol 92 (14) ◽  
pp. 4035-4040 ◽  
Author(s):  
M. A. Lowe ◽  
J. S. Alper
Keyword(s):  
Circular Dichroism ◽  
Force Field ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Field Dependence ◽  
Propylene Oxide ◽  
Vibrational Circular Dichroism ◽  
Circular Dichroïsm

Skeletal vibrational circular dichroism of a series of bicyclic dilactones: the fingerprint region?

1998 ◽  
Vol 76 (6) ◽  
pp. 717-725 ◽  
Author(s):  
A Rauk ◽  
J L McCann ◽  
H Wieser ◽  
P Bour ◽  
Yu.I. El'natanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Circular Dichroism ◽  
Force Field ◽  
Ab Initio ◽  
Vibrational Circular Dichroism ◽  
Coupled Oscillator ◽  
Field Perturbation ◽  
Fingerprint Region ◽  
Circular Dichroïsm ◽  
Magnetic Field Perturbation

The vibrational circular dichroism (VCD) spectra of 2,5-dioxabicyclo[2.2.1]heptane-3,6-dione 1 (R = H) and the 1,4-dialkyl derivatives, 1 (R = Me) and 1 (R = t-Bu), were calculated by the ab initio magnetic field perturbation (MFP) procedure with a B3LYP/6-31G* force field, and the VCD spectra of the dimethyl and di-t-butyl derivatives were measured in the region 800-1500 cm-1. While the absolute configurations of 1 (R = Me) and 1 (R = t-Bu) could be assigned unambiguously by comparison of the experimental and predicted spectra, there is little obvious correspondence between the spectra of the series of compounds. The VCD spectra are analysed on the basis of operation of a coupled oscillator mechanism involving motions of the polar bonds. In the case of the parent dihydro system, bridgehead C-H bond motions appear to dominate contributions to the VCD of vibrational transitions into which they are mixed.Key words: vibrational circular dichroism (VCD), 2,5-dioxabicyclo[2.2.1]heptane-3,6-dione, dilactones, optical activity.

scholarly journals Absolute Configuration of Bromofluoroiodomethane after Preparative Gas Chromatographic Separation

2021 ◽  
Author(s):  
Benjamin Spenger ◽  
Stefan Näf ◽  
Stole Manov ◽  
Jürgen Stohner
Keyword(s):  
Gas Chromatography ◽  
Circular Dichroism ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Absolute Configuration ◽  
Chromatographic Separation ◽  
Vibrational Circular Dichroism ◽  
Preparative Scale ◽  
Circular Dichroïsm ◽  
Gas Chromatographic Separation

The enantiomers of bromofluoroiodomethane (CHBrFI) were separated on a preparative scale using gas chromatography (GC). The collected single enantiomers were analysed by vibrational circular dichroism spectroscopy and polarimetry in combination with ab initio calculations to determine the respective absolute configuration.

Electronic and Vibrational Circular Dichroism of Model β-Lactams: 3-Methyl- and 4-Methylazetidin-2-one

1996 ◽  
Vol 50 (5) ◽  
pp. 630-641 ◽  
Author(s):  
Jennifer McCann ◽  
Arvi Rauk ◽  
Gennadii V. Shustov ◽  
Hal Wieser ◽  
Danya Yang
Keyword(s):  
Circular Dichroism ◽  
Ab Initio ◽  
Electronic Transition ◽  
Vibrational Circular Dichroism ◽  
Protic Solvent ◽  
Free Energies ◽  
Chiroptical Properties ◽  
Circular Dichroïsm ◽  
Rotational Strengths ◽  
Simple Modeling

The chiroptical properties of the simplest chiral β-lactams, 3- and 4-methylazetidin-2-one, 1 and 2, respectively, were investigated. The experimental vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectra were measured and compared with ab initio predictions. Both compounds were found to form dimers with calculated binding enthalpies and free energies of about −51 kJ/mol and −6 to −8 kJ/mol, respectively. The experimentally measured IR and VCD spectra were measured in concentrated nonpolar (CCl4) solution and are in agreement with the predicted IR and VCD spectra of the dimeric forms, 12 and 22, but not the monomers. The most intense dimer VCD bands originate from in-plane N-H wags, which perturb the H-bonded cyclic array. At the more dilute concentrations employed for the ECD spectra, the experimental ECD spectra in heptane were interpreted satisfactorily as arising from a mixture consisting predominantly of monomers. In protic solvent (H2O, MeOH), the ECD spectra are consistent with H-bonded monomers. Simple modeling suggests that the rotational strengths of the first electronic transition gain most of their intensity from the nonplanarity of the amide chromophore, the contributions of which follow a spiral rule previously enunciated.

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