Effectiveness of Ultrasound-Assisted Synthesis of 4-ethyl-4-chloro Chalcone and Its Antibacterial Activity Elfi Susanti VH, Sri Mulyani, Sri Retno Dwi Ariani, Suryadi Budi Utomo, Muhammad Hizbul Wathon, Widiastuti Agustina Eko Setyowati, Annisa Zahronita Utami
Universitas Sebelas Maret
Abstract
This study aimed to synthesize and evaluate the antibacterial activity of 4-ethyl-4-chloro chalcone using ultrasonic irradiation as an environmentally friendly and energy-efficient approach. The Claisen-Schmidt condensation reaction was carried out between 4-ethylacetophenone and 4-chlorobenzaldehyde in ethanol with NaOH as a base catalyst at room temperature. The reaction results showed an increase in synthesis efficiency compared to conventional methods, with a shorter reaction time and higher yield. The structure of the synthesized compound was confirmed by FTIR, H, and C NMR spectroscopy, which revealed the presence of α-,β--unsaturated carbonyl groups characteristic of chalcones. Antibacterial activity was conducted against Escherichia coli (a Gram-negative bacterium) and Staphylococcus aureus (a Gram-positive bacterium) using the disc diffusion method. The test results showed that 4-ethyl-4-chloro chalcone produced an inhibition zone of 15.5 mm against E. coli and 11.4 mm against S. aureus. This value indicates that the compound is more active against E. coli than S. aureus, possibly due to the highly lipophilic nature of the ethyl (-C₂-H₅-) and chloro (-Cl) groups, which increases its ability to penetrate the bacterial lipid membrane. Based on the results of this study, the ultrasonic-assisted synthesis method has been proven effective in producing chalcone compounds with potential antibacterial activity, supporting the application of the sonochemical approach in the synthesis of environmentally friendly bioactive compounds.
