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  • Fenchone, camphor, 2-methylenefenchone and 2-methylenecamphor: a vibrational circular dichroism study.

Fenchone, camphor, 2-methylenefenchone and 2-methylenecamphor: a vibrational circular dichroism study.

The journal of physical chemistry. A (2006-04-14)
Giovanna Longhi, Sergio Abbate, Roberto Gangemi, Egidio Giorgio, Carlo Rosini
ABSTRACT

We report and discuss the infrared (IR) vibrational circular dichroism (VCD) spectra of the enantiomeric pairs of the olefin derivatives of fenchone (1,3,3-trimethyl-2-methylenebicyclo[2.2.1]heptane) and camphor (1,7,7-trimethyl-2-methylenebicyclo[2.2.1]heptane), respectively, together with those of the parent molecules. The VCD spectra were taken in three spectral regions: the mid-IR region, encompassing the fundamental deformation modes, the region of CH-stretching fundamental modes and the NIR-region between 1100 and 1300 nm, which corresponds to the second CH-stretching overtone. The VCD and absorption spectra in the first two regions are analyzed by use of current density functional theory (DFT) calculations. The NIR region is analyzed by a protocol that consists of the use of DFT-based calculations and in assuming local mode behavior: the local mode approach is found appropriate for interpreting the absorption spectra and, for the moment, acceptable for calculating NIR-VCD spectra. The analysis of the first region allows us to track the contribution of the C=O group in the vibrational optical activity of C-C stretching modes; notable differences are indeed found in olefins and ketones. On the contrary, in the other two regions the VCD spectra of olefins and ketones are more similar: in the normal mode region of CH stretching fundamentals the spectra are determined by the mutual orientation of the CH bonds; in the second overtone local mode region olefins and ketones signals show some differences.

MATERIALS
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Supelco
(+)-Fenchone, analytical standard
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Sigma-Aldrich
(+)-Fenchone, purum, ≥98.0% (sum of enantiomers, GC)
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Sigma-Aldrich
L-Fenchone, ≥98%
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Sigma-Aldrich
(1R)-(−)-Fenchone, ≥98%
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