FT-IR and FT-Raman spectra of 2-hydroxyethyl methacrylate – A conformational and vibrational analysis

• Optimized geometries of 2-hydroxyethyl methacrylate were obtained by DFT.
• Six stable conformations are found.
• Calculated and scaled vibrational normal modes.
• A comparison between the experimental and the computed spectra is made.
• Band assignment is made with the help of PED calculations.

A conformational search of the flexible 2-hedroxyethyl methacrylate molecule by semi-empirical AM1 and B3LYP formalisms leads to six stable conformations. Four of them are in the s-trans conformation. The optimized geometries at DFT using 6-311+G∗∗ basis set are in good agreement with experimental electron diffraction data of the methyl methacrylate molecule, thereby the s-trans is the most stable form.The harmonic frequencies at the fully optimized geometries of all conformers have been performed at the DFT//B3LYP/6-311+G∗∗ level of theory. Infrared and Raman intensities and potential energy distributions of the scaled harmonic frequencies are used for the assignment of the observed IR and Raman bands. We noticed a good agreement between the experimental and the computed spectra. The strong band at 1081 cm−1, in the infrared spectrum, maybe used as a characteristic band of the s-trans conformation. Henceforth, the less stable structure contribute alone for reproducing the Raman bands located at 276 (sh) and 3020 (vw) cm−1.

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