Correlation Engine 2.0
Clear Search sequence regions


  • esters (4)
  • fourier transform (1)
  • fruit (3)
  • methyl (10)
  • microwaves (1)
  • Sizes of these terms reflect their relevance to your search.

    The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm-1 and 415 cm-1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methyl internal rotation of methyl hexanoate to those of other CH3-O-(C=O)-R molecules leads to the conclusion that though the barrier height is relatively constant at about 420 cm-1, it decreases in molecules with longer R.

    Citation

    Nhu-Ngoc Dang, Hoang-Nam Pham, Isabelle Kleiner, Martin Schwell, Jens-Uwe Grabow, Ha Vinh Lam Nguyen. Methyl Internal Rotation in Fruit Esters: Chain-Length Effect Observed in the Microwave Spectrum of Methyl Hexanoate. Molecules (Basel, Switzerland). 2022 Apr 20;27(9)

    Expand section icon Mesh Tags

    Expand section icon Substances


    PMID: 35565991

    View Full Text