Interpretation of vibrational and NMR spectra of allyl acrylate: An evidence for several conformers

• Published in: Vibrational spectroscopy 2009-07, Vol.50 (2), p.231-244
• Main Authors: Jamróz, Michał H., Jamróz, Małgorzata E., Rode, Joanna E., Bednarek, Elżbieta, Dobrowolski, Jan Cz
• Format: Article
• Language: English
• Subjects: Allyl acrylate; Conformers; DFT; NMR; PED; Raman
• ISSN: 0924-2031; 1873-3697
• DOI: 10.1016/j.vibspec.2009.01.001

The mid-IR, far-IR, and Raman spectra of allyl acrylate were measured and interpreted with support of the B3LYP/aug-cc-pVDZ calculated anharmonic vibrational spectra followed by the potential energy distribution analysis. The experimental 1H and 13C NMR spectra of allyl acrylate dissolved in CDCl 3 or C 6D 6 were interpreted by means of the B3LYP/aug-cc-pVDZ-su2 calculated NMR chemical shifts and J( 1H, 1H) and J( 1H, 13C) coupling constants. Exactly ten stable allyl acrylate conformers (five s- cis and five s- trans) were found after careful B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ scan of the conformational space. The experimental IR and Raman spectra are in good agreement with the theoretical spectra of the most stable conformers 1 with a presence of the second stable conformer 2, both exhibiting cis arrangement of the acrylic moiety. There are however two bands in the IR spectra, at ca. 1270 and 1260 cm −1, that definitely indicate the conformers with trans arrangement of the acrylic moiety to be present in liquid allyl acrylate. The bands at ca. 2990 and 1650 cm −1 are suggested to be due to Fermi resonances engaging CH and C C stretching vibrations, respectively. The careful inspection of the room temperature 1H and 13C NMR spectra of allyl acrylate suggest that a dominating form of the allyl acrylate molecule in an inert solvent exhibits the cis conformation of the acrylic moiety and an extended allyl group.