“…The υC = O [48] is usually found at 1750-1650 cm −1 and these are assigned at 1685, 1666 cm −1 (IR), 1675 cm −1 (Raman), 1671, 1669 cm −1 (DFT) for BZL, 1720, 1660 cm −1 (IR), 1660 cm −1 (Raman), 1667, 1665 cm −1 (DFT) for DMB, 1670, 1655 cm −1 (IR), 1672, 1658 cm −1 (Raman), 1668, 1666 cm −1 (DFT) for DFB, 1665 cm −1 (IR), 1670, 1667 cm −1 (DFT) for DCB and at 1670, 1650 cm −1 (IR), 1669, 1666 cm −1 (DFT) for DBB. For the title compounds, the ring breathing modes for para-substituted phenyl ring are assigned at 808 cm −1 (IR), 810, 788 cm −1 (Raman), 812, 787 cm −1 (DFT) for DMB, 805 cm −1 (IR), 808 cm −1 (Raman), 810, 806 cm −1 (DFT) for DFB, 835, 766 cm −1 (IR), 832, 769 cm −1 (DFT) for DCB and at 833, 763 cm −1 (IR), 829, 764 cm −1 (DFT) for DBB [49, 50]. The ring breathing mode of the mono substituted phenyl ring is assigned at 1013, 1006 cm −1 (IR), 1000 cm −1 (Raman) and at 1009, 1003 cm −1 (DFT) for BZL [51, 52, 53].…”