Investigation of Infrared Spectroscopy and Raman Spectroscopy for Functional Group Identification and Structural Confirmation of Trisubstituted Benzaldehyde

Abstract

Background
Vibrational spectroscopy gives organic molecules unique identifying marks on their structures (Schrader, 1995). The infrared bands become apparent by measuring the changes to the dipole moment of a molecule as it vibrates (Atkins & de Paula, 2002); whereas, Raman bands become apparent by measuring the changes in polarizability of a molecule as it vibrates (Albrecht, 1961).
Objective
The IR and Raman spectra are employed to describe the 2-hydroxy-3,4- dimethoxy-benzaldehyde, identifying functional groups and ensuring that the structure is correct (Silverstein et al., 2016).
Methods
IR-band assignments are based on established group-frequency correlations as well as region references (Banwell, 1966), while Raman-mode assignments are based on aromatic skeletal markers and substituent markers. (Schrader, 1995). All the band-mode assignments were verified using bond-strength and force-constant relationships (Badger, 1934).
Results
Raman and IR spectroscopy confirm an O-H group (phenolic), C=O carbonyl (aldehyde), and C-O bond (methoxy) presence in this sample (Silverstein et al., 2016). Strong C=C and ring breathing vibrational features were observed with Raman spectrometry (Schrader, 1995). Bands observed by IR and Raman spectroscopy correlated with one another (Banwell & McCash, 1994).
Comparison with Literature
The location of bands corresponds well with the range of frequencies for aromatic aldehydes and substituted phenyls reported (Silverstein et al., 2016), indicating that minor shifts in band positions may be attributable to Hydrogen Bonding/Substitution (Badger, 1934). A recent publication indicates that much improved analysis of spectral information can now be completed through an application of current Spectroscopic methods (Darmawan et al, 2025; Wang et al., 2025).
CONCLUSION
The combination of IR and Raman Spectroscopy represents a definitive means for characterizing the tested compound (Schrader 1995), and the data presented here will allow for further computer-generated modelling and comparative analysis of Vibrational Spectroscopy (Henschel et al., 2020).