Simulations on the structure, vibrations and electronic properties of 1,2–epoxy–3–phenoxy propane and 1,2–epoxy–3–( p –tolyloxy)propane by FT–IR, FT–Raman, FT–NMR and DFT methods

Abstract

Abstract Complete structural, electronic and vibrational properties of 1,2–epoxy–3–phenoxy propane (EPOP) and 1,2–epoxy–3–(p–tolyloxy)propane (ETOP) molecules have been investigated with the help of FT–IR, FT–Raman and FT–NMR spectra of the compounds with the support of the theoretical calculations carried out by DFT/B3LYP method of calculations with 6–311 + + G** and cc–pVTZ basis sets. Various possible conformers of the compounds are determined by analyzing the potential energy profile. In EPOP, the stable conformer I is more stable than the second II by 0.1776 kcal mol–1. Similarly, the conformer I of ETOP is more stable than the conformer II 0.8435 kcal mol–1. The various modes of vibrational frequencies are assigned and analysed with the help of FT–IR and FT–Raman spectra. The electronic properties, such as HOMO and LUMO energies are determined. In both the cases of EPOP and ETOP, the HOMO space distribution reveals that all the carbon atoms of the phenyl ring, the methyl carbon atom and the methylene hydrogen atoms H8 and H9 are more favourable for electrophilic attack. The lone pair donor orbital, n(O10) → π*C11–C16 interaction in EPOP is strongly stabilised by 29.34 kcal mol–1. In the case of ETOP compound, πC12–C13 → π*C11–C16 interaction has more stabilisation energy, 21.34 kcal mol–1. The stabilisation energy of lone pair donor orbital, n(O10) → σ*C11–C16 is 28.80 kcal mol–1. 1H and 13C chemical shifts of the molecules are calculated by GIAO method and discussed. For EPOP, the hydrogen atoms H4, H5 and H6 present in the epoxy ring shows peaks at 2.72, 2.85 and 3.32 ppm, respectively. In the case of ETOP the epoxy hydrogen shows up field peak at 2.70, 2.84 and 2.30 ppm, because of the presence of hyperconjugative effect of the methyl group. The chemical reactivity and site selectivity of the molecule has been determined with the help of global and local reactivity descriptors. The Δfk, Δsk and Δωk values of ETOP suggests that C14 and C11 carbon atoms are more prone to nucleophilic attack while in EPOP the Δfk and Δωk values shows that C14 and C11 is the active sites for the nucleophilic attack but Δsk is only favourable for C11 and not for C14 atom.