Combination of functional group between hydroxyl-aromatic and prenyl in certain compounds or materials, according to literature research analysis, would have antibacterial property. Conjugation of tyrosine and citronellal to produce new compound which has antibacterial activity has been done. The result was embedded chemically onto neutral material surface so that the combined materials have antibacterial activity. However, the product of conjugation has low antibacterial activity. Therefore, computational chemistry analysis was deployed to investigate the effectiveness of reaction. Computational analysis was done by electronic quantum and application of time dependent density functional theory (infra-red spectra analysis). This analysis was applied to the reactant and product. The analytical results were compared to the infra-red spectral experiment data. The findings show that there was the relevant result between computational analysis result and experimental data in particular to the both wave lengths and vibrational frequencies were still in range of the determinant functional groups range. In addition, the imine bond formation to the product which indicates that the conjugation has happened.