Assignment of the Molecular Absolute Configuration through the ab Initio Hartree−Fock Calculation of the Optical Rotation:  Can the Circular Dichroism Data Help in Reducing Basis Set Requirements?

Abstract

In this paper the calculation of the optical rotation (OR) of some rigid organic molecules, using the Hartree-Fock method with small (6-31G, DZP) basis sets, has been studied thoroughly to carefully evaluate the scope and limitations of this method, previously introduced by other authors. Calculations on test molecules (compounds 1-13) together with a careful analysis of their CD spectra allow a simple criterion for the reliability of this approach to be formulated: for unsaturated and/or aromatic (i.e., absorbing in the near-UV region) molecules, if the [alpha](D) is quantitatively determined by the lowest energy Cotton effect (at wavelengths >220 nm), then the HF/6-31G result is reliable. The usefulness of this method for the experimental organic chemist has been further demonstrated because the OR (sign and order of magnitude) of compounds 14-19 (i.e., large molecules having considerable interest in organic chemistry), which fulfill the above criterion and for which an extended basis set treatment is not feasible owing to their size, is correctly predicted.

In the Quest for a Virtual Pseudo Receptor for Sandalwood‐Like Odorants. Part I

“…The enantiomer ()-11ca was then used in one of their further reports [70], and its absolute configuration is not unambiguously depicted in [71]. Astonishingly, and without other explanation than quoting the reference of the racemic material [43], they later claimed that the antipode (À)-11ca is responsible for the sandalwood scent [72] and finally used this latter compound for further studies [73] [80]. The independent synthesis and olfactive evaluations of both pure enantiomers of 17ca,cb and 11ca,cb by asymmetric deprotonation [81] will be reported elsewhere by Dr. C. Margot.…”

Solvent effects on the conformational distribution and optical rotation of γ‐methyl paraconic acids and esters

“…The implementation of (frequency-dependent) linear response theory-specifically for the calculation of the chiroptical tensors-at various levels of theory, from Hartree-Fock 8,9 to Density Functional Theory (DFT) [10][11][12][13][14][15] and coupled cluster (CC) methods, 14,16,17,18 often together with the use of London atomic orbitals (LAOs) 19 to remove unphysical origin dependencies in the magnetic-field dependent quantities, has allowed the accurate (and reliable) determination of the rotatory power for a large number of molecular systems. [20][21][22][23][24] Several studies, in particular on rigid molecules, have shown that values of specific rotations as accurate as 63 deg cm 2 g À1 can be obtained if the molecular geometry is optimized at the DFT/Becke-3-parameter-Lee-Yang-Parr (B3LYP) 25 (DFT/B3LYP) level using a basis set of (at least) 6-31G** quality, and the ORs are determined using time-dependent (TD)-DFT/B3LYP and a basis set of (at least) aug-cc-pVDZ quality. 11,24,26,27 Complications might arise when the systems under investigation are ''flexible''-that is, they exist in more than one stable conformation.…”

A Comparative Study of Overtone CH-Stretching Vibrational Circular Dichroism Spectra of Fenchone and Camphor

“…[1][2][3][4][5][6][7][8][9][10][11][12] We had already published in the past some NIR-VCD data for 1 and 2 and for some related compounds. 13,14 However, we have recently improved our apparatus for measuring NIR-VCD, obtaining better VCD data in the overtone region at ∆V ) 3, new VCD data at ∆V ) 4 for fenchone, and VCD data in the yet unexplored regions of CH-stretchings/HCH-bendings combinations.…”