Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1 H, 13 C NMR) investigations of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane V. Arjunan a,⇑ , R. Anitha b , L. Devi c , S. Mohan d , Haifeng Yang e a Department of Chemistry, Arignar Anna Government Arts & Science College, Karaikal 609 605, India b Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Puducherry 605 008, India c Research and Development Centre, Bharathiar University, Coimbatore 641 046, India d School of Sciences and Humanities, Vel Tech University, Avadi, Chennai 600 062, India e Department of Chemistry, Shanghai Normal University, Shanghai 200234, China highlights  (1,2-Epoxyethyl)benzene (EEB) and (1,2-epoxy-2-phenyl)propane (EPP) have been studied.  The conformations of the molecules are titled.  The tilt angle of the phenyl ring in EEB is 74.4° and in EPP is 23.6°.  The barrier height between more and less stable conformers in EEB is 3.01 kcal mol 1 .  The barrier height between more and less stable conformers in EPP is 3.47 kcal mol 1 . graphical abstract article info Article history: Received 4 May 2014 Received in revised form 25 June 2014 Accepted 2 July 2014 Available online 10 July 2014 Keywords: FTIR FT-Raman NMR (1,2-Epoxyethyl)benzene (1,2-Epoxy-2-phenyl)propane abstract Aromatic epoxides are causative factors for mutagenic and carcinogenic activity of polycyclic arenes. The 1,2- or 2,3-epoxy compounds are widely used to a considerable extent in the textile, plastics, pharmaceutical, cosmetics, detergent and photochemical industries. The FTIR and FT-Raman spectra of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane are recorded in the regions 4000–400 cm 1 and 4000–100 cm 1 , respectively. The observed fundamentals are assigned to different normal modes of vibration. The structure of the compound has been optimised with B3LYP method using 6-311++G ** and cc-pVTZ basis sets. The IR and Raman intensities are determined. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/6- 311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of the compounds has been performed to indicate the presence of intramolecular charge transfer. The 1 H and 13 C NMR chemical shifts of the molecules have been analysed. Ó 2014 Elsevier B.V. All rights reserved. Introduction Epoxides (oxiranes, ethylene oxides, oxacyclopropanes) belong to the most widely used functional groups in organic synthesis. http://dx.doi.org/10.1016/j.saa.2014.07.001 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +91 413 2211111, mobile: +91 9442992223; fax: +91 413 2251613. E-mail address: varjunftir@yahoo.com (V. Arjunan). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 120–136 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa