Vibrational spectroscopy investigation using ab initio and density functional theory on p-anisaldehyde

Area of Science:

• Molecular Spectroscopy
• Computational Chemistry
• Organic Chemistry

Background:

• p-Anisaldehyde is an aromatic aldehyde with applications in synthesis and fragrance.
• Understanding its molecular vibrations is crucial for identifying the compound and its interactions.
• Spectroscopic techniques combined with theoretical calculations offer a comprehensive approach to molecular analysis.

Purpose of the Study:

• To record and analyze the FTIR and FT Raman spectra of p-anisaldehyde.
• To perform theoretical calculations for optimized geometry and vibrational frequencies.
• To assign and validate the observed vibrational bands using computational methods.

Main Methods:

• Experimental recording of FTIR (4000-400 cm⁻¹) and FT Raman (3500-100 cm⁻¹) spectra.
• Ab initio and Density Functional Theory (DFT) calculations using the 6-31G(d,p) basis set.
• Complete relaxation in the potential energy surface for accurate geometry optimization.

Main Results:

• Optimized geometry and vibrational band intensities were calculated.
• A comprehensive vibrational assignment was proposed based on theoretical harmonic frequency analysis.
• Calculated harmonic vibrational frequencies showed good agreement with experimental FTIR and FT Raman spectra.
• Experimental spectra satisfactorily matched theoretically constructed bar spectrograms.

Conclusions:

• The combined experimental and theoretical approach successfully validated the vibrational assignments for p-anisaldehyde.
• The study provides a detailed spectroscopic profile of p-anisaldehyde.
• This work serves as a reference for future studies involving p-anisaldehyde and related compounds.